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A guide to the scienti ic and medical research into McArdle Disease explained in plain English This handbook explains in layman s terms the cause method of inheritance history and current and future treatments of McArdle disease also known as Glycogen Storage Disease Type V The handbook puts into plain English the published information about McArdle Disease which is normally written in technical language as it is aimed at medical or scienti ic professionals Some sections are necessarily still rather technical but in general the handbook should be understandable to those without any medical or scienti ic training It is fully referenced to the source publications The AGSD UK is grateful to the Vodafone Foundation s World of Difference programme which allowed the winner to prepare this handbook Old Hambledon Racecourse Sheardley Lane Droxford Southampton SO32 3QY Telephone 0300 123 2790 Registered charity no 1132271 Further copies of this book are available via www agsd org uk Ask about other languages v 1 1 1a AGSD UK Kathryn Birch Ph D is a scientist who has worked on McArdle Disease for four years She completed a Ph D creating cell models of McArdle disease During her studies she read most of the papers published on McArdle disease building an up to date knowledge of the historical and current scienti ic and medical research on the condition She has attended McArdle Clinics and AGSD UK Annual Conferences during which she has met dozens of people with McArdle disease and learned from their experiences Kathryn Elizabeth Birch Ph D Each chapter has an introduction which summarises the coming pages as simply as possible Then more detail is given in the chapter text using slightly more technical language The McArdle Disease Handbook The McArdle Disease Handbook The McArdle Disease Handbook A guide to the scienti ic and medical research into McArdle Disease explained in plain English Kathryn Elizabeth Birch Ph D

First published August 2011 Version 1 1 1 published August 2015 Published by Association for Glycogen Storage Disease UK Ltd Old Hambledon Racecourse Sheardley Lane Droxford Hants SO32 3QY Registered Charity number 1132271 Company limited by guarantee registered in England number 698112 www agsd org uk ISBN 978 0 9569658 1 3 Copyright Kathryn Birch 2011 2015 For personal use only not to be copied distributed or sold in any form without the prior permission of the author and publisher In case of discrepancies between the different language versions of the Handbook the English version is the original version and will prevail Disclaimer Unless otherwise stated this Handbook represents the views and opinions of the author Kathryn Birch and does not represent the views and opinions of AGSD UK or Vodafone World of Difference The purpose of this Handbook is to explain scientific research and knowledge about McArdle disease in layman s language so that it can be understood by people with McArdle disease or those interested in McArdle disease It is not intended to replace medical advice from your family doctor or specialist The information provided in this Handbook is correct to the best of the author s knowledge If you have any doubts about the accuracy of the information in this Handbook it is recommended that you read the original source full details in the reference list Where no definitive information is available the author has sought to suggest scientific rationale behind anecdotal observations reported by people with McArdle s It is stated where a theory or opinion of the author is given Due to the nature of scientific research current theories and understanding of the science behind McArdle s may change over time and subsequently be proven or disproven It is recommended that you check the AGSD UK website frequently to ensure you are reading the most up to date version of this Handbook Page 2 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Cover pictures Left People with McArdle disease can experience severe muscle damage which is indicated by raised creatine kinase levels There is a risk of kidney damage so hospitalisation may be required Stacey Reason and Dan Chambers have both experienced severe muscle damage with creatine kinase levels of over 200 000 IU L about a thousand times the normal level Right By working to regain their fitness creating a high aerobic capacity and learning helpful techniques like the use of walking poles as shown here Stacey Reason and Dan Chambers completed the 210 mile Walk over Wales in the summer of 2010 Some people with McArdle s cannot achieve these results and remain badly affected ongoing research is trying to find the answers Thanks to Stacey and Dan for permission to use their photos Centre McArdle disease is caused by an absence of muscle glycogen phosphorylase McArdle disease can be diagnosed by muscle biopsy A chemical reaction is carried out which produces a red purple colour if muscle glycogen phosphorylase enzyme is present Muscle biopsy photographs are reproduced by kind permission of Professor Caroline Sewry Great Ormond Street Hospital London and RJAH Orthopaedic Hospital Oswestry Centre top Normal muscle showing muscle glycogen phosphorylase enzyme Centre bottom Muscle of a person with McArdle disease showing absence of the enzyme Definitions of terms used in this Handbook In this Handbook McArdle person is used to mean a person who has received a definitive diagnosis of McArdle disease who has no functional muscle glycogen phosphorylase enzyme in their skeletal muscle cells McArdle people have two faulty copies of the PYGM gene In a McArdle person both copies of the PYGM gene contain a mutation which prevents functional muscle glycogen phosphorylase being made Unaffected by McArdle s is used in this Handbook to describe a normal person who has no mutations in either copy of the PYGM gene People unaffected by McArdle s have two normal copies of the PYGM gene Normal copies of the PYGM gene contain no mutations and can be used to make functional muscle glycogen phosphorylase People unaffected by McArdle s have a normal amount of functional muscle glycogen phosphorylase in their muscle cells Carrier is used to describe a person who has one normal copy of the PYGM gene without any mutations and one faulty copy of the PYGM gene which contains a mutation A carrier is likely to have approximately half the normal level of muscle glycogen phosphorylase Carriers do not usually have symptoms of McArdle disease Further definitions are given where appropriate throughout the Handbook There is also a glossary at the end of the Handbook for scientific or medical words used frequently in the Handbook which would not be included in a standard English glossary The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 3

Acknowledgements I would like to acknowledge Vodafone World of Difference UK charitable foundation for providing two months funding for this project I would like to thank the AGSD UK for supporting my application for funding Thanks especially to Andrew Wakelin AGSD UK McArdle Co ordinator for his comments on the draft version of the Handbook My Ph D project funded by AGSD UK and The Institute of Orthopaedics RJAH Orthopaedic Hospital Oswestry provided me with an opportunity to develop an interest in McArdle disease I would like to thank all the McArdle people who have shared their experiences with me and asked the most interesting and fundamental questions Thanks also to Mum Dad and Madelyn for their continued interest and encouragement and comments on the Handbook I am very grateful to my husband James Birch for his endless patience and support Funding for this project Kathryn Birch nee Wright submitted a proposal and successfully obtained funding from the Vodafone World of Difference charitable foundation under the World of Difference UK scheme This grant enabled AGSD UK to employ Kathryn Birch from January to March 2010 to write this Handbook Further writing was carried out by Kathryn Birch on an unpaid voluntary basis Kathryn Birch has no competing financial or academic interests Comments and feedback about this Handbook To contact the author please visit the AGSD UK web site at www agsd org uk and use the Contact Us page choosing McArdle Disease Handbook Page 4 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Contents Chapter Page 1 Introduction to McArdle disease 7 2 Symptoms and diagnosis of McArdle disease 13 3 The genetics of McArdle disease 33 4 Exercise muscle contractions and contractures muscle cramps 49 5 Muscle damage causes raised creatine kinase levels and myoglobinuria 59 6 Sources of energy in muscle cells 65 7 Dietary supplements which have been considered for McArdle s 85 8 The effect of age on the symptoms of McArdle disease 95 9 Differences in severity of symptoms between people 107 10 Mental and emotional aspects of McArdle disease 119 11 The effect of McArdle s on sexual activity pregnancy and birth 129 12 Medicines activities and other things which may be a greater risk for McArdle people 137 13 McArdle disease may increase the chances of having some diseases and conditions 143 14 McArdle s specialists and family doctors 151 15 Models of McArdle s can be used to test treatments 157 16 Potential therapies for McArdle disease 161 17 Details about this Handbook and the information in it 175 18 Glossary 183 19 References 187 20 Index 205 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 5

Visit the McArdle Disease pages on www agsd org uk for information and regular updates Page 6 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

1 Introduction to McArdle disease McArdle disease is caused by the lack of the muscle glycogen phosphorylase enzyme in muscle cells This enzyme is a special protein which plays a key role in changing glycogen into glucose in the muscle cells Glucose can then be used to provide energy to allow the muscle to contract and generate movement In McArdle people muscle glycogen phosphorylase does not function During exercise the muscle cells of McArdle people use up all their energy and are not able to generate further energy The short term lack of glucose causes tiredness and stiffness in muscles of McArdle people when they carry out exercise and can lead to muscle pain and muscle breakdown Without muscle glycogen phosphorylase the glycogen which is stored in the muscle cells cannot be changed into glucose The glycogen therefore accumulates in the muscle cells which is the reason why McArdle disease is known as a glycogen storage disease McArdle disease is named after Dr Brian McArdle a doctor who published the first medical paper describing his patient who had this muscle disease The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 7

1 1 A brief introduction to McArdle disease Muscle contractions are required to generate movement Muscle cells require a source of energy in order to perform muscle contractions Anaerobic exercise is a short burst of high intensity effort such as a sprint for a bus During anaerobic exercise glucose within muscle cells is broken down to produce ATP ATP is the source of energy for muscle cells The breakdown of glucose to produce ATP is called glycolysis However only a small amount of glucose is present in the muscle cells and this is used up within a few minutes of anaerobic exercise Muscle cells also contain much larger stores of glycogen Glycogen can be converted into glucose by a process called glycogenolysis In people unaffected by McArdle disease the process of converting glycogen into glucose requires several enzymes one of which is called muscle glycogen phosphorylase McArdle disease is caused by the lack of the muscle glycogen phosphorylase enzyme in muscle cells In McArdle people muscle glycogen phosphorylase is either absent or not functional The muscle cells are not able to convert the stored glycogen into glucose The muscle cells therefore run out of glucose and run out of energy The short term lack of glucose causes tiredness and stiffness in muscles of McArdle people when they carry out anaerobic exercise Rommel et al 2006 but this improves once exercise ceases McArdle people must rest until energy ATP is produced in the muscle cells by another method such as fatty acid oxidation or until glucose is obtained through the blood from the liver A period of rest is necessary because these other methods are slower to produce energy than glycogenolysis the method which normally involves muscle glycogen phosphorylase Once these other methods begin to replenish the amount of ATP in the muscle cells McArdle people can continue to exercise This is known as a second wind Amato 2003 However if McArdle people continue to exercise without rest the muscle cells use up all the available ATP and have no energy source available This can lead to breakdown of muscle cells rhabdomyolysis and muscle cramps fixed contractures both of which cause McArdle people to experience muscle pain Following rhabdomyolysis the components of the broken muscle cells are released into the bloodstream An enzyme normally found in muscle cells called creatine kinase CK also known as creatine phosphokinase CPK is released into the bloodstream following muscle damage A blood test performed by a family doctor or at a hospital can be used to measure the amount of CK in the blood which can be used as an indicator of the extent to which muscle damage has occurred The components of the broken muscle cells are transported through the bloodstream to the kidneys Myoglobin is another protein released from broken muscle cells Myoglobin is transported in the bloodstream to the kidneys where it is removed from the body in the urine resulting in dark red cola coloured urine known as myoglobinuria or proteinuria A rare but serious effect of extreme muscle damage is that broken muscle cells may block the filtration system of the kidneys preventing them working and resulting in kidney failure Martin et al 2001 DiMauro et al 2002 Quinlivan et al 2008 1 2 What is the cause of McArdle disease McArdle disease is caused by the absence of the muscle glycogen phosphorylase enzyme Mommaerts 1956 Schmid et al 1959 An enzyme is a protein which has a special function of Page 8 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

changing or breaking down one compound to another Muscle glycogen phosphorylase breaks down glycogen into glucose 1 phosphate A mutation in the PYGM gene which is responsible for muscle glycogen phosphorylase prevents the production of functional muscle glycogen phosphorylase 1 3 McArdle disease is one of the family of glycogen storage diseases There are many enzymes involved in the breakdown of glycogen into glucose If a mutation occurs in the enzyme which prevents it from functioning it will result in an inability to break down glycogen and its components to form glucose Diseases caused by a mutation in an enzyme required to break down glycogen are called glycogen storage diseases GSDs The glycogen storage diseases identified to date are listed in Table 1 1 There is further information about the glycogen storage diseases on the AGSD UK website http www agsd org uk The major symptom of every glycogen storage disease is an intolerance to exercise Glycogen storage is characteristic of all the diseases except GSD 0 Tarnopolsky et al 2006 described McArdle disease as the most common glycogen storage disease GSD VIII is caused by a mutation in phosphorylase b kinase Phosphorylase b kinase is essential for activation of the muscle glycogen phosphorylase enzyme However disease symptoms for GSD VIII are not very similar to McArdle disease possibly because there are difference mechanisms for activation of muscle glycogen phosphorylase in the absence of phosphorylase b kinase Orngreen et al 2009 1 4 Why is it called McArdle disease McArdle disease is named after Dr Brian McArdle the British family doctor who first published a paper describing a patient with the disease In 1951 Dr McArdle described a 30 year old male patient for whom light exercise caused pain in the muscles and continued exercise led to weakness and stiffness Pain during exercise would occur in any muscle in the body the most noticeable being in the arms or legs The pain would force the patient to stop and rest but it was noted that after a period of rest the patient was then able to exercise further Dr McArdle realised that after exercise the lactate lactic acid level of the patient did not increase as expected and that glycogenolysis was incomplete He also noticed that the patient s muscles were very weak even though they had quite a large bulk His astonishingly perceptive theory was that it is the enzyme system that is at fault it seems that the patient has a disorder of carbohydrate metabolism during exercise a change took place in the muscle chemistry which effectively led to a breakdown in glycogenolysis McArdle 1951 Mommaerts et al 1956 realised that McArdle disease was caused solely by the loss of muscle glycogen phosphorylase not the loss of any other related enzymes Schmid et al 1959 took samples of different skeletal muscles from a McArdle person muscles located between the back and shoulder middle of the back and the calf and found there was a lack of functional glycogen phosphorylase in all of these muscles He tested the different enzymes involved in the breakdown of glycogen and identified the cause of the disease as the loss of the ability to produce glucose 1 phosphate because muscle glycogen phosphorylase wasn t functional The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 9

y of the glycogen storage diseases identified to date Page 10 Kathryn Birch Debranching enzyme Andersen disease Branching enzyme Liver glycogen phosphorylase Phosphofructokinase Phosphorylase b kinase lack of one of the PHKA2 four subunits Glucose transporter GLUT2 Table 1 1 Summary of the glycogen storage diseases identified to date Fanconi Bickel syndrome G6PC G6PT1 AGL GBE1 PYGM PFK The McArdle Disease Handbook Version 1 1 1 The McArdle Disease Handbook Version 1 1 1 GYS2 Kathryn Birch Gene name Page 10 PFK Phosphorylase b kinase lack of one of the PHKA2 four subunits Glucose transporter GLUT2 Phosphofructokinase PYGL Liver glycogen phosphorylase GBE1 AGL PYGM Glucose 6 phosphate translocase Muscle glycogen phosphorylase Branching enzyme Debranching enzyme Glucose 6 phosphatase Phosphorylase b kinase deficiency Tarui disease Hers disease G6PT1 G6PC GYS2 Gene name Endoplasmic reticulum inorganic NPT I NPT II NPT III not fully phosphate transporter determined 1 4 glucosidase and 1 6 glucosidase GAA Glycogen synthase GSD XI Muscle glycogen phosphorylase McArdle disease Andersen disease Cori disease Pompe disease Deficient enzyme GSD IX Fanconi Bickel syndrome GSD VII Phosphorylase b kinase deficiency GSD VI and X Hers disease GSD V Cori disease Glucose 6 phosphate translocase Alternative name GSD IV Pompe disease Endoplasmic reticulum inorganic NPT I NPT II NPT II phosphate transporter determined 1 4 glucosidase and 1 6 glucosidase GAA Glucose 6 phosphatase Von Gierke disease GSD III McArdle disease GSD II GSD Ic Tarui disease GSD Ib Glycogen synthase Deficient enzyme Von Gierke disease Alternative name GSD Ia GSD 0 Glycogen Storage Disease e Disease PYGL

1 4 1 Other names for McArdle disease McArdle disease is also known as McArdle s McArdle syndrome McArdle s syndrome Muscle Phosphorylase Deficiency Myophosphorylase Deficiency Phosphorylase Deficiency McArdle Myopathy McArdle s Myopathy Muscle Glycogen Phosphorylase Deficiency and Glycogen Storage Disease GSD type V It may be called MacArdle s but this is incorrect because it is named after Dr Brian McArdle Myopathy is a general name for muscle disease 1 4 2 Other names and abbreviations for muscle glycogen phosphorylase Glycogen phosphorylase Phosphorylase muscle phosphorylase a and b myophosphorylase PYGM GP M MGP alpha 1 4 glucan orthophosphate glycosyltransferase or EC 2 4 1 1 1 5 How can I explain my McArdle disease to my friends and family who have never heard of it before This is my suggestion of how I would describe it to friends and family who haven t heard of McArdle disease before Your muscles use glucose to provide energy to move There isn t much glucose in your muscles so after a couple of minutes of vigorous anaerobic exercise the glucose is all used up There are also stores of glycogen in the muscle and there is an enzyme called muscle glycogen phosphorylase which normally changes the glycogen into glucose which gives the muscles more energy to continue to exercise In people with McArdle disease this enzyme doesn t work so the muscles run out of energy and can t get any more If the McArdle people continue to exercise the muscles basically starve and can be damaged However if the McArdle person rests for a short period the muscles can get energy from glucose in the blood or from other sources such as fat which is stored in the body The McArdle person can then continue to exercise 1 6 The future is promising for people with McArdle disease The future is positive for McArdle people In the 60 years since Brian McArdle published the first paper describing McArdle disease a lot of research into understanding McArdle s has been done as outlined in this Handbook There are research groups around the world carrying out research into McArdle s These range from research into brain functioning by Drs Quinlivan and Edelstyn in the UK to the investigations into exercise and diet by Drs Vissing and Haller in Denmark and the US to Prof Howell and colleagues carrying out research to increase the amount of a different form of glycogen phosphorylase the brain isoform using a drug called valproate in the McArdle sheep in Australia In the shorter term there are some excellent specialists who are highly knowledgeable about McArdle s and can offer up to date advice on diet and exercise for people with McArdle s The internet has also enabled people with McArdle disease to compare symptoms and advice and to provide support with others around the world through online patient support groups Research into improving everyday life with McArdle s is ongoing including investigating whether other genes phenotype modulators may have an effect upon the severity of symptoms In the longer term many different avenues for treatment are being considered including correcting the The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 11

expression of muscle glycogen phosphorylase which contains a mutation or replacing it with the brain glycogen phosphorylase enzyme Online resources There is information about McArdle disease and the other glycogen storage diseases on the AGSD UK website http www agsd org uk Page 12 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

2 Symptoms and diagnosis of McArdle disease The typical symptom of McArdle disease is pain caused by anaerobic exercise e g repetitive movements rapid movements or holding a pose The onset of pain occurs within a few minutes of exercise If the McArdle person does not stop and rest then prolonged exercise can cause painful cramps and red cola coloured urine may be seen a few hours later If a McArdle person interrupts exercise with short rests they then can get into a second wind which will then allow them to continue to exercise for longer The presence of a second wind is unique to McArdle disease so it can be used by a specialist as a clue to suggest a diagnosis of McArdle disease At present diagnosis is most commonly by muscle biopsy and or DNA testing A muscle biopsy is an invasive procedure but has the advantage that one sample can be used to test for many different muscle diseases DNA testing is usually targeted to a specific area of the DNA so is more appropriate if McArdle disease is already suspected DNA testing is highly accurate and becoming more commonly used DNA is usually obtained from a blood sample so is minimally invasive As McArdle disease is rare many McArdle people are misdiagnosed before they receive the correct diagnosis of McArdle disease Diseases which McArdle people are misdiagnosed with can include other muscle diseases diseases which cause inflammation of the muscles or chronic fatigue The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 13

2 1 The personal history of symptoms described by a typical McArdle person A typical McArdle person will have pain which occurs within a few minutes of anaerobic exercise They will remember these symptoms from childhood Often they will have struggled in sports lessons at school Children with McArdle s have great difficulty in carrying out activities such as cross country running if their teacher does not allow them to rest and get into a second wind Outside of school many McArdle children and adults will have developed coping mechanisms to allow themselves to rest without other people noticing These techniques could include frequently pretending to tie up their shoelace stopping to look in shop windows or pretending to use a mobile phone Some McArdle people will have discovered the second wind phenomenon they will have learnt that if they rest when they feel muscle pain they are then able to continue to exercise for a much longer period of time Some McArdle people will not have experienced the second wind phenomenon but all are able to experience it if taught Quinlivan and Vissing 2007 Most McArdle people will have experienced fixed contractures stiff contracted enlarged muscles often following more intense exercise Examples of exercise which is likely to lead to contractures includes intense activity such as running for the bus repetitive activity such as chewing or peeling potatoes or an activity where the muscles hold the body in one place for a long time such as squatting or some yoga positions Some McArdle people will have experienced dark red cola coloured urine which is particularly likely after a muscle contracture Some McArdle people will have attended a hospital emergency department because of the cola coloured urine and contractures In rare cases they may have had kidney failure and required dialysis McArdle people typically find that a very sedentary lifestyle makes it more of a struggle to perform any exercise They may find that if they keep fit they are able to do more However at the other extreme intense exercise can make the muscles very painful forcing the McArdle person to rest for many days while the muscles repair and recover After this period of time they may then find that exercise is harder and the muscles feel weaker than before For most McArdle people the symptoms remain similar throughout their life although some muscle weakness may occur as they get older The above description is a combination of information published by Quinlivan and Vissing 2007 Lucia et al 2008a and information from McArdle people provided to me via online discussion groups 2 1 1 Activities which McArdle people have reported can cause pain fatigue in muscles Here are some examples of activities which McArdle people have said can cause pain or fatigue in muscles activities are taken from published papers and from internet chat groups and e mail conversations This is a brief list designed to give some examples of the types of activities Page 14 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Repetitive movements Holding a pose Rapid movements Repetitive movements Chewing McArdle 1951 Holding a opr ose Squatting crouching Chewing Using can McArdle opener 1951 Squatting oon r tciptoes rouching Standing Rapid movements Running Lucia et al 2008a such as running for the bus Running t al 2e008a such Climbing sLucia tairs eLucia t al 2008a as running for the bus Climbing stairs Lucia et al p2ausing 008a Very brisk walking without to rest Lucia et al 2008a Very brisk walking without pausing to rest fLucia et aa bl 2008a Cycling ast on ike Using can teeth opener Standing n tiptoes Brushing Lucia et Lifting a hoeavy weight such as al 2008a carrying a box bag Lucia Brushing teeth Lucia et Lifting 2008 a heavy weight such as al 2008a carrying a bpox bag Grating cheese or peeling Some yoga oses Lucia 2008 vegetables Grating heese or which peeling yoga oses Cycling fast published on a bike papers Table 2 1 cActivities causeSome muscle painpfor McArdle people Taken from references vegetables in brackets and personal communication with McArdle people unreferenced Table 2 1 Activities which cause muscle pain for McArdle people Taken from published papers references in brackets and personal communication with McArdle people unreferenced 2 2 Symptoms of McArdle disease The of McArdle are dwisease ell characterised and are summarised below Exceptions 2 2 symptoms Symptoms of Mdisease cArdle include some reported cases of late onset symptoms which are discussed further in section 8 1 3 The symptoms of McArdle disease are well characterised and are summarised below Exceptions Differences in severity of symptoms have been reported and possible explanations are discussed in include some reported cases of late onset symptoms which are discussed further in section 8 1 3 section 9 Differences in severity of symptoms have been reported and possible explanations are discussed in section 9 Very common symptoms of McArdle disease seen in almost all McArdle people Very symptoms of M isease seen in vaery lmost all M cArdle people common Exercise intolerance mcArdle uscles bdecoming tired quickly and running out of energy Lucia et al 2008a Exercise intolerance muscles becoming tired very quickly and running out of energy Lucia et al 2008a Continued exercise causing painful cramps contractures Lucia et al 2008a Continued exercise painful cramps contractures et a l 2008a Myoglobinuria dark causing red cola coloured urine after intense eLucia xercise Lucia et al 2008a say that the colour of urine due to myoglobinuria has been described by McArdle people as Myoglobinuria dark red cola coloured urine after intense exercise Lucia et al 2008a say looking like cola marsala or red wine that the colour of urine due to myoglobinuria has been described by McArdle people as looking plike miarsala red wine Muscle ain dcola uring ntense oer xercise will usually have existed since childhood Quinlivan and Vissing 2007 Muscle pain during intense exercise will usually have existed since childhood Quinlivan and Vissing w2ith 007 People McArdle s are able to experience a second wind if they exercise gently to warm up and rest when they feel pain they will then find that they can exercise for a much People with McArdle s are able to experience a second wind if they exercise gently to longer period It should be noted that a second wind is unique to McArdle disease Lucia warm up and rest when they feel pain they will then find that they can exercise for a much et al 2008a However some McArdle people do not know how to get into a second wind longer period It should be noted that a second wind is unique to McArdle disease Lucia or do not realise that this is occurring unless guided through it by a family doctor or et al 2008a However some McArdle people do not know how to get into a second wind specialist Quinlivan and Vissing 2007 or do not realise that this is occurring unless guided through it by a family doctor or specialist Quinlivan and Vissing 2007 High levels of creatine kinase CK in the blood at rest even when a McArdle person has not exercised intensely for hours or even days Lucia et al 2008a say that 100 of McArdle High levels of creatine kinase CK in the blood at rest even when a McArdle person has not people have average CK levels above 200U l and approximately 50 of McArdle people exercised intensely for hours or even days Lucia et al 2008a say that 100 of McArdle have average CK above 1000U l See section 5 3 2 for further information on creatine people have average CK levels above 200U l and approximately 50 of McArdle people kinase have average CK above 1000U l See section 5 3 2 for further information on creatine kinase The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 15 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 15

Occasional instances of very high levels creatine kinase CK in the blood Lucia et al 2008a define very high as being in the region of several thousand U l This is likely to be detected hours or days after the McArdle person has performed an intense exercise Less common symptoms of McArdle disease seen only in some McArdle people Some McArdle people have fixed proximal weakness Fixed proximal weakness is found in approximately 33 of people with McArdle disease Lucia et al 2008 It has not been possible to find a definition of fixed proximal weakness but I believe that in this context fixed means non reversible permanent and proximal is used to describe the muscles closest to the trunk of the body such as the shoulder and around the pelvis A feature rather than a symptom is the fact that some McArdle people find that they are able to exercise more easily if they have had a high sugar glucose drink or eaten carbohydrates such as pasta or rice prior to exercise Lucia et al 2008a Some of the more severe symptoms which can lead to diagnosis of McArdle disease 2 3 Kidney renal failure due to rhabdomyolysis and myoglobinuria can lead to hospital investigations which result in a diagnosis of McArdle s Biller 2007 Type of test Ischaemic non i Muscle pain myalgia inflammation myositis and damage caused by statins drugs taken exercise test to lower cholesterol can sometimes lead to hospital investigations which result in a diagnosis of McArdle disease Biller 2007 Cycle ergometer Diagnosis of McArdle disease exerci McArdle disease can be suspected based on a person having the symptoms described above or if Treadmill a sibling has already been diagnosed with McArdle disease There are several methods used to diagnose McArdle disease A brief description of each along Muscle biopsy s with the pros and cons and limitations is given in Table 2 2 They are not listed in any particular order An indication of how commonly I believe each method is used to diagnose McArdle s is also Muscle biopsy e given DNA genetic tes Creatine Kinase Electromyogram Magnetic resona 31P MRS Table 2 2 Method and relevant notes Page 16 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

ds to diagnose McArdle disease An overview of my opinion of how commonly each method is used whether it produces a defin s m EMG Sometimes used ance spectroscopy Rarely used enzyme activity test Rarely used Recently become one of the most common methods Very commonly used Sometimes used ise test Rarely used The McArdle Disease Handbook Version 1 1 1 Very commonly used Creatine Kinase blood test Yes No No No Principally used by scientists investigati which occur in the muscle cells during e Requires complex and expensive equipm Used predominantly in the UK McArdle Kathryn Birch No No Use of this test was first described by D and has been in use for about 50 years Principally used by scientists investigating changes which occur in the muscle cells during exercise Requires complex and expensive equipment High success rate at producing a definitive diagnosis Not very invasive Can be prohibitively expensive but likely to become cheaper in the future CK is invariably raised in McArdle disease so this simple blood test is a useful first sign that something needs investigating Not diagnostic and relevant notes Page 17 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 17 Table 2 2 Methods to diagnose McArdle disease An overview of my opinion of how commonly each method is used whether it produces a definitive diagnosis Rarely used High success rate at producing a definit Not very invasive Can be prohibitively likely to become cheaper in the future CK is invariably raised in McArdle diseas blood test is a useful first sign that som investigating Not diagnostic Magnetic resonance spectroscopy 31P MRS Looks for lack of enzyme and excess of success rate at producing a definitive d invasive method of diagnosis High risk of inaccurate result Requires biopsy Often used by scientists in the Sometimes used No Yes Probably not Yes Recently become one of the most common methods Often used by scientists testing the effe or diet No Electromyogram EMG Looks for lack of enzyme and excess of glycogen High success rate at producing a definitive diagnosis Most invasive method of diagnosis High risk of inaccurate result Requires invasive muscle biopsy Often used by scientists in the past Used predominantly in the UK McArdle s clinic Often used by scientists testing the effects of exercise or diet Use of this test was first described by Dr Brian McArdle and has been in use for about 50 years Notes Notes Probably not Yes No No No Will a positive result definitively diagnose McArdle s No DNA genetic testing Very commonly used Muscle biopsy enzyme activity test Rarely used r exercise test Very commonly used Rarely used Sometimes used Very commonly used Very commonly used Will a positive result definitively diagnose McArdle s No ischaemic forearm Muscle biopsy staining of slides Treadmill exercise test Cycle ergometer exercise test staining of slides How often is this test used to diagnose McArdle s blood test Ischaemic non ischaemic forearm exercise test Type of test sting How often is this test used to diagnose McArdle s

2 3 1 Exercise test There are three types of exercise test a forearm test a cycling test or a treadmill All three are intended to test whether the body is able to break down glycogen to produce glucose in order to provide the muscles with energy during exercise What is tested When a muscle of an unaffected person is exercised vigorously anaerobic exercise the free glucose is rapidly used up Stored glycogen is then broken down by the process of glycogenolysis to produce energy During glycogenolysis lactate and pyruvate are produced In people unaffected by McArdle s the amount of lactate lactic acid and pyruvate should increase 5 6 fold Dubowitz et al 2007 Glycogenolysis is required to produce the rise in lactate and pyruvate levels In McArdle people the absence of functional muscle glycogen phosphorylase blocks glycogenolysis McArdle people therefore do not have the expected increase in lactate and pyruvate levels In the ischaemic forearm test a cuff is used to reduce blood flow to the arm Ischaemic means to reduce blood flow It is performed as an ischaemic test to prevent the blood bringing glucose or fatty acids to the muscle This ensures that anaerobic not aerobic exercise occurs However recent studies have shown that similar results with less risk of muscle damage can be achieved with a non ischaemic forearm test Niepel 2004 Cons of all exercise tests The level of effort must be below the maximum so that severe complications like rhabdomyolysis and myoglobinuria do not occur Fernandes 2006 Following exercise increased ammonia levels increased uric acid levels see section 13 1 for the relationship between uric acid levels and gout and increased creatine kinase are often seen Milunksky 2010 Limitations The exercise tests do not definitively diagnose McArdle disease An a bsence of increase in lactate and pyruvate levels indicates a metabolic disease caused by a block in glycogenolysis Many other glycogen storage diseases prevent lactate production after anaerobic exercise Lane 1996 The exercise test does not distinguish whether the person has McArdle disease or another other metabolic disease for example another glycogen storage disease such as Tarui disease phosphofructokinase deficiency Abramsky 2001 Cori disease and Tarui disease can produce flat not increasing lactate levels after the forearm test Biller 2007 If a small increase in lactate 1 5 3 fold of resting levels and a very high increase in ammonia occurs it may suggest that the person has a disease where a small amount of enzyme is still functional examples of these diseases would be phosphoglycerate mutase phosphoglycerate kinase and lactate dehydrogenase deficiencies Abramsky 2001 A different disease called myoadenylate deaminase deficiency MADD is another metabolic disease characterised by decreased ammonia production Lane 1996 MADD is discussed further in section 9 3 2 If a person with MADD exercises the amount of lactate will increase and the amount of ammonia will be lower than expected Lane 1996 Abramsky 2001 For this reason the level of ammonia in the blood plasma ammonia is usually measured before and after an ischaemic forearm test Lane 1996 Page 18 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

2 3 1 1 Ischaemic or non ischaemic forearm exercise test How the ischaemic forearm test is carried out A pre test blood sample is taken before the test A cuff tight band is put around the forearm or occasionally the thigh The forearm is contracted by squeezing a ball or balloon or the thigh is contracted at maximum force strength for one minute or until extreme pain The cuff is then loosened Blood samples are taken for example at 1 3 5 and 10 minutes after exercise The blood is analysed to determine whether the expected increase in lactate and pyruvate occurs After exercise the amount of lactate in the blood will not increase Cush 2005 in McArdle people but McArdle people will have an increase in ammonia levels in the blood which can go up to 360 560 g dl Lane 1996 It is important that ammonia levels in the blood rise as this shows that the person has exercised enough as an incorrect result could be obtained if the person who is being tested does not exercise with enough effort Lane 1996 Cons of the ischaemic forearm test The test can lead to muscle damage Cramping muscle pain and contracture of the muscle may occur following the test Cush 2005 There is a small risk of the severe problem of compartment syndrome discussed further in section 12 3 2 The risk of compartment syndrome is much lower if the non ischaemic forearm test is performed There is also a risk of the test causing severe muscle damage which could lead to kidney failure see section 5 for further information on rhabdomyolysis and kidney failure Meinck et al 1982 published a report where a 57 year old McArdle person was asked to perform an ischaemic forearm test The muscle of the tested forearm was damaged which resulted in myoglobinuria and raised creatine kinase levels in the blood The person was placed under medical observation and instructed to drink plenty of fluids Although kidney failure did not occur the authors Meinck et al 1982 warned that it could be a potential hazardous side effect of the ischaemic forearm test How the non ischaemic forearm test is carried out A non ischaemic forearm test similar to that described above but without use of a cuff is now recommended A study by Kazemi et al 2002 found that the non ischaemic forearm test was able to distinguish McArdle people from unaffected people The non ischaemic forearm test is much less likely to cause damage Niepel 2004 The ischaemic forearm test can cause a lot of pain and discomfort for McArdle people whereas the non ischaemic test produces almost no discomfort Abramsky 2001 Cons of the non ischaemic forearm test I think that it seems possible that muscle damage could also be a side effect of the non ischaemic forearm test if the person exercises too vigorously as described by Meinck et al 1982 for the ischaemic forearm test Pros of both the ischaemic and non ischaemic forearm exercise tests It is not very invasive the only invasive part is taking blood samples It can be performed with relatively simple equipment Cons of both the ischaemic and non ischaemic forearm exercise tests If people who don t have McArdle s are very weak or are unmotivated during the exercise test no increase in lactate and pyruvate may be seen resulting in an incorrect diagnosis of McArdle disease Lucia et al 2008a It may produce a positive result in people with other similar diseases which affect glycogenolysis or glycolysis like some of the other glycogen storage disease The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 19

Only works for children old enough to squeeze the ball balloon It was suggested by Lane 1996 that false negative results could be seen in the rare cases of McArdle people with low levels of functional muscle glycogen phosphorylase but no experimental data was provided to support this theory If both lactate and ammonia increase only a small amount it suggests that either the person being tested did not put enough effort into the exercise or that the wrong vein was used to sample the blood The correct vein to use is called the median cubital vein and one example of an incorrect vein to use is the basilica vein Abramsky 2001 The blood samples must be assayed quickly so it is essential that the test is performed at a location near to a biochemistry laboratory Barnes 2003 2 3 1 2 Cycle ergometer exercise test A cycle ergometer is a static bike commonly found in a gym Pedalling turns a wheel which runs over a band The band can be tightened to provide more resistance making it harder work to pedal and increasing the amount of energy the person needs to move the pedals energy is measured as Watts W What is tested This test measures whether exercise leads to an increase in lactate and pyruvate in the blood In addition breathing apparatus is often used to quantify the amount of oxygen used for exercise VO2max How the cycle ergometer test is carried out McArdle people have very low work capacities so the cycle ergometer should be precisely adjusted to provide a low amount of resistance 0 50W The person begins to pedal gently with the amount of resistance being increased by 5 10W every other minute The person being tested wears a type of oxygen mask over their head This allows measurement of the amount of oxygen they breathe in oxygen consumption called VO2 and the amount of carbon dioxide breathed out called VCO2 These two numbers can be combined to produce a VCO2 VO2 ratio A heart rate monitor can be used to measure heart rate A blood sample is taken prior to exercise and after exercise to find out the lactate levels in the blood Abramsky 2001 If the blood lactate levels do not rise it may suggest a diagnosis of McArdle s or Tarui disease To determine which of these diseases a person has the person is asked to briefly exercise at maximum capacity which is called VO2max The person is then asked to exercise at approximately 40 of VO2max Abramsky 2001 In McArdle people this level of exercise causes a high heart rate and a high level of perceived exhaustion it feels like really hard work to pedal until 8 10minutes into the exercise when the second wind occurs At this point 8 10mins into exercise McArdle people have a dramatic drop in heart rate and it feels much easier to exercise pedal even though they are pedalling at the same rate as before It can be further tested by increasing the resistance making the band tighter so that the person has to pedal even harder This causes the persons heart rate to increase In some experiments the person is then given intravenous glucose glucose via a needle and drip in the arm 50ml of a 50 solution In McArdle people the glucose leads to a second second wind the heart rate will drop again and it will feel easier to pedal again Page 20 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

These changes in heart rate and second wind are diagnostic of McArdle disease In Tarui disease a second wind does not occur and intravenous glucose makes it harder for the person to exercise Abramsky 2001 To ensure that the person exercised is not working at their maximum level their pulse rate should be kept below 150 beats min for adults and 150 180 beats min for children Fernandes 2006 Pros of cycle ergometer for exercise tests pros are not specific to testing for McArdle disease Keeps person being tested in the same place so it is easy for them to wear a facemask which is used to monitor the amount of oxygen being breathed in and amount of carbon dioxide being breathed out It is also easier to take blood from the person as they are staying in the same place It is easy to use the cycle machine to accurately quantify the amount of exercise the person is doing adapted from Cooper and Storer 2001 For these reasons a cycle ergometer is often used by scientists testing the effect of diet or exercise on the ability of McArdle people to exercise for example Drs Haller and Vissing frequently publish papers using cycle ergometers e g Vissing et al 2009 Cons of cycle ergometer for exercise tests cons are not specific to testing for McArdle disease If people do not cycle regularly it may feel strange and may result in premature leg tiredness if it is an unfamiliar form of exercise adapted from Cooper and Storer 2001 Children have to be old enough to be able to cycle 2 3 1 3 Treadmill test How the test works This is similar to the ischaemic non ischaemic forearm tests and also similar to the cycle ergometer test What is tested The treadmill test is used to measure presence of second wind effect of exercise on heart rate and to test whether exercise leads to muscle pain Breathing apparatus can be used to measure the amount of oxygen breathed in and carbon dioxide breathed out used to calculate VO2 max Perez et al 2009 How the treadmill test is carried out The person being tested walks on a treadmill The speed of the belt and the slope of the belt level of inclination can be adapted so that the person is walking at a speed of 3 5km h with a pulse rate of 150 180beats min The length of time that it takes for the person to become exhausted can indicate which disease they may have Glycogen storage diseases will make people exhausted more rapidly whereas diseases caused by defects in fatty acid oxidation will make people feel exhausted later Fernandes 2006 Pros of the treadmill test It can be used to test very young children as soon as they can walk Fernandes 2006 Perez et al 2009 Everyone is used to walking around so it is a very natural and familiar way to test Cooper and Storer 2001 Cons of the treadmill test It can be harder to measure oxygen and carbon dioxide It is perhaps harder to obtain blood samples Note At the UK McArdle s Clinic the treadmill test was sometimes used by experienced physiotherapists to teach McArdle people how to achieve a second wind if they had not previously experienced second wind before personal observation at the clinic while located at the RJAH Orthopaedic Hospital in Oswestry UK The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 21

2 3 2 Muscle biopsy What is tested A muscle biopsy can be used to test for two things 1 An accumulation of glycogen McArdle people and people with other glycogen storage diseases apart from GSD 0 have an accumulation of glycogen within the muscle cells Unaffected people have a much lower amount of glycogen in their muscle cells 2 An absence of functional muscle glycogen phosphorylase in the muscle cells Unaffected people have a high level of muscle glycogen phosphorylase in their muscle cells How is the muscle biopsy test carried out The McArdle person is placed under either local or general anaesthetic A surgeon removes a piece of muscle from one of the large muscles such as the upper arm thigh or calf The piece of muscle is sent to a histology department who will preserve it if necessary and carry out the necessary tests To confirm the validity of the test the enzyme must be seen in either an internal control a blood vessel or an external control muscle tissue from someone who is known not to have any muscle disease The family doctor or specialist should then be sent a report from the histology department outlining the results It should be noted that muscle biopsies can either be taken as a needle biopsy a hollow needle is used to cut and remove a sample of the muscle or as an open biopsy a surgeon cuts and removes a small sample of muscle A needle biopsy is normally smaller than an open biopsy is likely to cause less damage to the muscle and have a quicker healing time A needle biopsy is recommended by Dubowitz and Sewry Heckmatt et al 1984 Dubowitz et al 2007 Some textbooks recommended that a muscle biopsy be performed in the most symptomatic area Cush 2005 However in theory I think that it shouldn t matter which muscle the biopsy is taken from because if a person has McArdle s muscle glycogen phosphorylase is missing not functional in all the skeletal muscles of the body Surgeons usually chose to biopsy the thigh calf or bicep because they are large muscles so it is easier to take a small biopsy without damaging any surrounding tissue Cons of the muscle biopsy test Malignant hyperthermia is an inherited condition whereby some anaesthetic drugs produce an adverse reaction which includes an extreme rise in body temperature see section 12 3 1 McArdle people are at an increased risk of having malignant hyperthermia like symptoms which can cause a dangerous reaction to general anaesthetic It is important to remind inform your surgeon of this risk prior to surgery Dubowitz and Sewry 2007 recommend muscle biopsy be performed under local anaesthetic which reduces risk of side effects like malignant hyperthermia Limitations An inaccurate result may be obtained if muscle biopsy is performed shortly after a period of rhabdomyolysis and muscle damage If muscle damage has occurred prior to the biopsy being taken small immature regenerating muscle fibres may be seen which are positive for the phosphorylase stain due to expression of other isoforms of glycogen phosphorylase enzyme Lane 1996 An explanation of the other isoforms of glycogen phosphorylase is given in section 6 5 Serial sections pieces of tissue cut from the same muscle biopsy sample can be stained with antibodies for other immature proteins such as myosin which will confirm that these fibres are Page 22 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

immature Dubowitz et al 2007 It is not possible to distinguish between the different isoforms of glycogen phosphorylase enzyme in the phosphorylase staining test Testing a muscle biopsy shortly after rhabdomyolysis has occurred is likely to result in a false negative result a person who really does have McArdle disease will be told that there is nothing wrong with them Notes It should be noted that McArdle disease cannot be diagnosed by skin biopsy This is because McArdle disease only affects skeletal muscle cells Skin cells have a different form of glycogen phosphorylase It would be advisable to ask request that the muscle biopsy is stored by the laboratory carrying out the tests in liquid nitrogen or a 80 freezer as appropriate until the diagnosis is confirmed If there are any questions or uncertainty about the diagnosis the stored muscle biopsy can be used to perform further tests This eliminates the need for a further biopsy 2 3 2 1 Staining of slides with slices of muscle What is tested Following a muscle biopsy thin slices of muscle are made and mounted onto thin glass slides The muscle fibres can be stained to determine the amount of glycogen present A special stain called the periodic acid Schiff PAS stain DiMauro et al 2002 Dubowitz et al 2007 is used to stain glycogen A chemical reaction is carried out to determine whether there is functional muscle glycogen phosphorylase in the muscle fibres Amato 2003 Muscle glycogen phosphorylase is used to produce a compound which can be stained to produce the purple brown colour If the muscle glycogen phosphorylase is not functional it will not produce this compound and no colour will be seen After staining the slides with slices of muscle will be examined under a microscope It is important that the laboratory carrying out these tests performs the same tests on a biopsy from an unaffected person a negative control at the same time This removes the possibility of a false negative test if some part of the test does not work correctly Pros of the staining of slides with slices of muscle test If the phosphorylase staining is carried out correctly it will provide an accurate and specific diagnosis of McArdle disease An absence of muscle glycogen phosphorylase is diagnostic of McArdle disease It will work whether the mutation is known or a brand new mutation which has not been identified before One muscle biopsy can also be used to test for and exclude many different muscle diseases Cons of the staining of slides with slices of muscle test It should be noted that an accumulation of glycogen will be seen from almost all the glycogen storage diseases and therefore is not diagnostic of McArdle disease The site of the biopsy may be painful until healed and may cause a scar It is more invasive than any of the other tests 2 3 2 2 Enzyme activity test How is an enzyme activity test carried out It is also possible that the amount of functional muscle glycogen phosphorylase in muscle biopsy sample can be tested in a different way A biopsy sample is taken as described below Instead of making thin slices the sample is homogenised mashed up The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 23

and a chemical reaction is carried out to measure how much functional muscle glycogen phosphorylase is present if any This technique is not used very commonly Pros of an enzyme activity test It may be possible to use it for diagnosis It may be easier to quantify a very low level of functional glycogen phosphorylase but with the limitation described below Cons of an enzyme activity test One limitation with this technique is that it will also detect other isoforms of glycogen phosphorylase which is found in the blood vessels in muscle These other isoforms of glycogen phosphorylase may produce a false positive result I think that there is no advantage of the enzyme activity test over the usual staining of slides with slices of muscle biopsy test 2 3 3 DNA testing How is DNA tested for McArdle disease DNA may be tested in various ways either looking for specific mutations within a gene using a Polymerase Chain Reaction PCR based test or using genetic sequencing to search the whole genome for mutations PCR is a laboratory technique whereby a small amount of DNA can be amplified into a large amount For the PCR based technique a DNA sample is first amplified using PCR and then special proteins called restriction enzymes are used to cut up the DNA Each enzyme will only cut one particular DNA sequence for example it may cut DNA with the mutation but not DNA with the normal sequence The sample can then be analysed if the enzyme has cut the DNA it indicates that it contains the mutation Genetic DNA sequencing is a different modification of a PCR based test which can be u sed to determine the exact genetic sequence of a gene This sequence can then be compared to a reference normal sequence and analysed to identify mutations How is the DNA test carried out A blood sample is taken DNA is prepared from the cells in the blood sample Tsujino et al 1993 The DNA is analysed in a laboratory either using the PCR based test or by genetic sequencing Pros of both types of DNA test This is a highly accurate test It causes very little pain during or after the test It is minimally invasive Pros of the PCR based DNA test It is relatively cheap once a laboratory has become familiar with the test It is relatively easy with standard laboratory equipment Cons of the PCR based DNA test A PCR based test will only identify common mutations It is only useful for populations where a few mutations commonly occur for example the R50X mutation is very common in the UK and North America It will not detect a less common mutation or a mutation which has never been detected or reported before It may be unavailable in some countries Pros of genetic sequencing It can be used to identify any all mutations even if they are rare or have never been reported before Recently sequencing has become much cheaper and is in the process of becoming an affordable method of diagnosis A gene is made up of both coding sequence Page 24 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

exons and non coding sequence introns with splicing sequence in between The splicing sequence should also be tested for mutations as an increasing number of mutations have been found in splicing sequence explained in further detail in section 3 2 4 Cons of genetic sequencing This is currently an expensive test It may be unavailable in some countries 2 3 4 Creatine kinase blood test What is tested Creatine kinase CK also known as creatine phosphokinase CPK is an enzyme a special kind of protein which is usually found within muscle cells If muscle cells are damaged then creatine kinase is released from the muscle cells into the blood How is the creatine kinase blood test carried out A blood sample is taken from the patient and sent to a hospital laboratory The blood is separated into serum which contains the creatine kinase and blood cells A chemical reaction is carried out to measure how much creatine kinase is present in the serum The amount of creatine kinase in the blood samples is expressed as units per litre of blood U l or international units per litre IU l Different hospital laboratories may carry out slightly different creatine kinase tests For each specific test it is useful to compare the result of your CK test with a reference level for the same test The reference level is the amount of creatine kinase which would be expected in a person unaffected by McArdle s who has not had any recent muscle damage Reference levels may vary by age gender ethnicity and amount of muscle the person has As a rough guide people unaffected by McArdle s have CK levels below 190 IU L Quinlivan et al 2010 or 220U l Miteff et al 2011 At rest McArdle people always have raised CK levels between 200U l and 1000 U l Lucia et al 2008a If a McArdle person carries out intense exercise which leads to rhabdomyolysis muscle damage CK levels can rise to several thousand U l Lucia et al 2008a In extreme cases of rhabdomyolysis McArdle people have anecdotally reported CK levels of hundreds of thousands U l Pros of the creatine kinase blood test It causes very little pain during or after the test It is minimally invasive A high creatine kinase provides an indication that muscle damage has occurred This can indicate a diagnosis of a muscle disease Cons of the creatine kinase blood test Raised creatine kinase levels are symptomatic of many muscle diseases including inflammation of the muscles and various muscular dystrophies so it cannot provide a specific diagnosis of McArdle disease High levels of creatine kinase may also be seen in people who do not have a muscle disease but who have recently undergone strenuous exercise or muscle injury for example from a car crash Table 5 1 in section 5 gives other causes of rhabdomyolysis muscle damage which could lead to raised creatine kinase levels in people unaffected by McArdle s Note In McArdle people the creatine kinase is released from skeletal muscles such as the muscles in your arms and legs However an alternative cause of raised creatine kinase levels can be a heart attack The heart is a different kind of muscle but can also release creatine kinase if damaged If the heart muscle is damaged by a heart attack also called a myocardial infarction this can lead to a raised level of creatine kinase In most cases a McArdle person will be aware that the raised The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 25

creatine kinase levels are probably due to damage of the skeletal muscles If a heart attack is suspected medical staff will be able to perform further specific tests Rhabdomyolysis and creatine kinase are discussed in further detail in section 5 2 3 5 Electromyogram EMG What is tested A muscle contraction occurs when an electrical impulse signal travels from a nerve to a muscle fibre or a set of muscle fibres A standard pattern of electrical activity is seen when a person unaffected by McArdle s contracts and relaxes their muscles A standard pattern of electrical activity is also seen in the muscles when an unaffected person is at rest Some muscle diseases affect the electrical impulses either by producing electrical activity when the muscles are at rest or by reducing the amount of electrical impulses seen Lane 1996 How is EMG test carried out An electromyogram EMG measures this electrical activity within muscles Surface electrode probes may be placed on the skin next to the muscle being tested or a very fine needle electrode is inserted in the muscle This probe electrode is connected to apparatus which measures the electrical impulses in the muscles Braakhekke et al 1986 performed the test on McArdle people as follows Surface EMG was performed on the quadriceps thigh muscle Two electrodes were placed 5cm apart The electric signal was recorded during exercise A computer was then used to identify bursts of electrical pulses The test detects whether the electrical waves are showing the normal expected pattern In the McArdle people an increase in EMG activity was seen during the first 6 to 7 min of exercise then stabilised EMG activity did not increase in unaffected p eople Braakhekke et al 1986 An increase in electrical activity was also seen in the bicep muscles of McArdle people during the ischaemic forearm test Linssen et al 1990 It has been suggested that as some muscle fibres use up their energy and become unable to contract the electrical signals increase to stimulate more muscle fibres to help the muscle move contract in McArdle people Braakhekke et al 1986 Unusual EMG readings were seen in approximately half 49 of McArdle people tested Darras and Friedman 2000 Pros of the EMG test If surface probes are used then it is non invasive Cons of the EMG test It has anecdotally been reported to be an uncomfortable test It does not provide a definitive diagnosis and would just suggest that a person may have McArdle disease Based upon the figures provided by Darras and Friedman 2000 51 of McArdle people have normal EMG If EMG were used to diagnose McArdle s half the people tested would receive a false negative diagnosis Different results may be seen depending which part of the muscle the electrodes are placed on or which muscle is tested Different muscles have different combinations of type I and type II fibres which can affect the EMG measurement Page 26 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

2 3 6 31P magnetic resonance spectroscopy 31P MRS This technique is not used routinely but a few papers report using 31P MRS to diagnose McArdle disease Greutter et al 1990 described the use of 31P MRS to diagnose children in a situation where both parents were known to have McArdle disease Ross et al 1982 also used 31P MRS to diagnose McArdle disease 31P MRS has been used by some scientists such as Martinuzzi 2007 and also Vorgerd et al 2000 to investigate the effects of treatments in McArdle people What is tested 31P MRS was used by Greutter et al 1990 to study the pH acidity within the muscle cells during exercise In unaffected people lactic acid is generated in muscles during exercise causing the pH to decrease as the contents of the muscle cells became more acidic In McArdle people the pH does not decrease and may increase slightly becoming more alkaline during exercise In McArdle people there is no decrease in intracellular pH after exercise low resting ATP and no accumulation of phosphomonoesters phosphorylated sugars Lane 1996 How is the test carried out The person being tested either lies on their back with the thickest part of their calf muscle within the MRS machinery or places their forearm inside the MRS machinery de Kerviler et al 1991 The MRS machinery is used to take a reading before exercise The person is then instructed to move their foot up and down with increasing force or contract their hand arm using hand grips The MRS machinery is then used to take another reading Pros This technique is non invasive Boesch 2007 31P MRS can be used to diagnose asymptomatic people with McArdle s Gruetter et al 1990 Cons 31P MRS cannot distinguish between other glycogen storage diseases for example it cannot be used to distinguish between McArdle disease and phosphofructokinase deficiency de Kerviler et al 1991 In most cases an ischaemic test is performed meaning that a cuff is used to reduce blood flow to the limb this could cause damage in the same way as described for the ischaemic forearm test section 2 3 1 1 31P MRS is time consuming and expensive Lane 1996 Use of MRS requires access to the specialist MRS equipment and staff trained to use it The MRS machinery is typically found in hospitals and some McArdle s clinics may not have the appropriate accessories and setting to perform 31P MRS Boesch 2007 2 4 Causes of similar symptoms to McArdle disease in people who don t have McArdle s Muscle pain and fatigue may be caused by many other diseases some of which are listed below section 2 5 2 Muscle damage and rhabdomyolysis muscle breakdown can occur in people unaffected by McArdle s and can be caused by many factors listed in more detail in section 5 including excessive exercise or as a side effect of the use of statins drugs taken to reduce cholesterol levels Blood in the urine could be caused by urinary tract infections e g cystitis Menstruation a woman having a period may also result in blood in the urine The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 27

Some foods such as beetroot beets rhubarb and blackberries may give urine a red colour Red coloured urine may also be seen if taking some medicines such as warfarin or laxatives containing senna 2 5 Other diseases which have similarities to McArdle disease Many McArdle people are misdiagnosed with a different disease before they are correctly diagnosed with McArdle disease Pavic et al 2003 carried out one study on McArdle people diagnosed between 1962 and 2002 and found that one third of these people had at least three muscle biopsies before the correct diagnosis was made The authors described some of the reasons why family doctors struggle to diagnose McArdle disease They say that muscle cell damage caused by McArdle disease may lead to inflammation A muscle biopsy may therefore look the same as other type of inflammatory muscle disease for example polymyositis Also they said that if muscle damage had caused the muscle cells to die cell death due to damage is called necrosis it may not be possible to see if glycogen storage has occurred Many people with McArdle disease are not diagnosed until adulthood although most have experienced symptoms from childhood Quinlivan et al 2007 Quinlivan et al 2010 It may be harder for children to obtain a diagnosis of McArdle disease In part this may be because muscle pain caused by exercise may be misdiagnosed as growing pains in children with McArdle disease Diagnosis of McArdle disease in children is discussed further in section 8 2 2 1 2 5 1 Some of the diseases which McArdle people have been misdiagnosed with before getting a proper diagnosis of McArdle s There are a few published cases of McArdle people who were initially misdiagnosed with another disease It is likely that most cases are not published because cases of misdiagnosis are not considered to be of interest to the medical community 2 5 1 1 Polymyositis O Brien et al 1998 reported two cases of men with McArdle s who had been misdiagnosed with an inflammatory myopathy thought to be idiopathic polymyositis idiopathic polymyositis is muscle inflammation with no known cause These men were aged 50 and 62 and did not report the classic symptoms of McArdle disease they said that they had had relatively late onset of symptoms They had both been prescribed immunosuppressants which is a treatment for idiopathic polymyositis They were later shown to have no muscle glycogen phosphorylase enzyme activity in their muscle biopsies Paradas et al 2005 reported a woman with McArdle s who had been misdiagnosed with polymyositis and treated with steroids prior to diagnosis of McArdle s 2 5 1 2 Refractory dermatomyositis G mez Cerezo et al 2008 reported a case of a 25 year old woman who was misdiagnosed as having refractory dermatomyositis refractory dermatomyositis is inflammation of muscles and skin which does not respond to treatment As well as McArdle s symptoms of muscle weakness and high CK level 93728 U l she had skin lesions on both arms which led to diagnoses by three independent family doctors that she had dermatitis She was treated with predisolone a steroid 60 mg day of prednisone 150 mg day of azathioprine and 7 5 mg week of methotrexate which Page 28 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

appeared to reduce the CK level A later biopsy showed absence of muscle glycogen phosphorylase confirmed by genetic identification of the mutations in the PYGM gene 2 5 2 Other muscle diseases with similar symptoms to McArdle disease Sometimes people are suspected of having McArdle disease but actually have another similar disease A very brief list of some of the diseases which have similar symptoms to McArdle disease is given in Table 2 3 2 6 McArdle disease was considered a possible diagnosis for a patient with chronic pain in the television series House The challenges of correctly diagnosing a patient with McArdle disease is mentioned in the television series House House is produced and distributed by Universal Playback House is a hospital drama which stars Hugh Laurie as Dr Gregory House a consultant who specialises in diagnosing patients whom no other consultants have been able to successfully diagnose In series 5 the episode called Painless focuses upon the diagnosis of a patient in chronic pain One suggestion by the medical team assisting House is that the patient may have McArdle disease Information about McArdle s is mostly described in an accurate way in this programme In the programme the family doctors hypothesise guess that the patient s pain could be caused by McArdle disease which they correctly described as a glycogen storage disease The patient is experiencing chronic pain throughout his body Chronic permanent pain is reported by some patients with McArdle s see 9 4 In the programme they say that there are muscle cells in the wall of the intestine which could lead to pain I am not sure that this statement is correct The intestine is made of smooth muscle which is unaffected by McArdle disease and therefore would not be painful However it is possible that there is skeletal muscle overlaying the intestine which would be affected by McArdle s and could be painful They correctly propose to test whether the patient has McArdle disease using the ischaemic forearm test this is a commonly used method to diagnose McArdle s and is discussed further in section 2 3 1 1 They take blood from the patient while he is undergoing the ischaemic forearm test and monitor the level of lactate in the blood The medical team tell the patient s wife that McArdle s can be treated with gene replacement therapy and lifestyle changes At present gene replacement therapy is not available as a treatment for McArdle s although it is being investigated by scientists as a potential therapy sees section 16 Lifestyle changes such as regular gentle aerobic exercise are recommended as a good treatment for McArdle s see section 4 2 2 So overall most of the information about McArdle disease given in this episode is correct or almost correct The popularity of this programme should mean that many more people will now have heard of McArdle disease and will have learnt a little about the disease The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 29

pathies Disorders of fatty ndrome le diseases with similar symptoms to McArdle disease Page 30 Characterized by glycogen storage apart from GSD 0 A group of inherited metabolic disorders in which harmful amounts of fatty materials called lipids accumulate in some of the body s cells and tissues A group of muscle diseases usually inherited which usually lead to muscle weakness in various different muscles of the body Myositis is a general term for inflammation of the muscles Many of these are considered to be caused by autoimmune conditions and are treated with immunosuppressant drugs In many cases these muscle diseases are not inherited Muscle diseases caused by defects in the mitochondria Mitochondria are a part of the cells which play an important role in producing energy These are inherited diseases caused by the lack of function of an enzyme which is needed to break down fatty acid to provide energy in muscle cells The primary symptom is extreme tiredness and fatigue It may also include muscle pain and feeling ill after exercise The cause is not known although it can sometimes begin after a virus or infection It is not believed to be an inherited disease Kathryn Birch Polymyositis Carnitine palmitoyltransferase I deficie Carnitine palmitoyltransferase II defici Medium chain acyl coenzyme A dehyd deficiency MCAD Short chain acyl coenxyme A dehydrog deficiency SCAD Chronic fatigue syndrome ME Post vi syndrome The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Carnitine palmitoyltransferase I deficiency CPT I Carnitine palmitoyltransferase II deficiency CPT II Medium chain acyl coenzyme A dehydrogenase deficiency MCAD Short chain acyl coenxyme A dehydrogenase deficiency SCAD Chronic fatigue syndrome ME Post viral fatigue syndrome Polymyositis Examples of some of the specific dise group Tarui disease Pompe disease The McArdle Disease Handbook Version 1 1 1 Gaucher disease Fabry disease Page 30 Table 2 3 Other muscle diseases with similar symptoms to McArdle disease Chronic fatigue syndrome Duchenne muscular dystrophy Limb girdle muscular dystrophy Gaucher disease Fabry disease Examples of some of the specific diseases in each group Tarui disease Pompe disease Brief description Mitochondrial myopathies Disorders of fatty acid metabolism Myositis Muscular dystrophies Lipid storage diseases Characterized by glycogen storage apart from GSD 0 A group of inherited metabolic disorders in which harmful amounts of fatty materials called lipids accumulate in some of the body s cells and tissues A group of muscle diseases usually inherited which usually lead to muscle weakness in various different muscles of the body Myositis is a general term for inflammation of the muscles Many of these are considered to be caused by autoimmune conditions and are treated with immunosuppressant drugs In many cases these muscle diseases are not inherited Muscle diseases caused by defects in the mitochondria Mitochondria are a part of the cells which play an important role in producing energy These are inherited diseases caused by the lack of function of an enzyme which is needed to break down fatty acid to provide energy in muscle cells The primary symptom is extreme tiredness and fatigue It may also include muscle pain and feeling ill after exercise The cause is not known although it can sometimes begin after a virus or infection It is not believed to be an inherited disease ies Glycogen storage diseases ses Brief description diseases General name for the group of diseases the group of diseases Duchenne muscular dystrophy Limb girdle muscular dystrophy

Online resources and recommended reading There is information about McArdle disease and the other glycogen storage diseases on the AGSD UK website http www agsd org uk There is information about McArdle disease and other muscle diseases including muscular dystrophies on the Muscular Dystrophy Campaign MDC website http www muscular dystrophy org about_muscular_dystrophy conditions Inborn metabolic diseases diagnosis and treatment by John Fernandes Jean Marie Saudubray Georges Van Den Berghe John H Walter For a brief description of each disease Google free books eases in each ency CPT I iency CPT II drogenase genase iral fatigue The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 31

Page 32 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

3 The genetics of McArdle disease McArdle disease is caused by the lack of functioning muscle glycogen phosphorylase enzyme Enzymes are a special kind of protein A gene is the piece of DNA that provides the instructions which the cell uses to produce a protein Each gene has a unique name and the gene for muscle glycogen phosphorylase is called PYGM McArdle disease is caused by mutations in the PYGM gene Different mutations in this gene can have different effects which can include creating a shortened version of the enzyme or a mixed up version of the enzyme with the wrong components In almost all cases this leads to a complete absence of functioning muscle glycogen phosphorylase The precise mutations which an individual has are usually determined by their ethnic background for example one mutation found in Japanese people is not found in British people McArdle disease is inherited in a recessive way This means that both parents must be carriers of a faulty copy of the PYGM gene in order for the child to inherit two faulty copies of the gene Parents who are carriers of a faulty copy of the PYGM gene will not have symptoms of McArdle disease and will probably be unaware that they are carriers There is a 25 chance that a child will have McArdle disease if both parents are carriers In practice this means that when a child is born with McArdle s disease they are usually the first person in the family to be affected The inheritance of McArdle s is not affected by gender so men and women are equally likely to inherit McArdle disease In a situation where one parent has McArdle disease but the other does not all the children will be carriers of McArdle disease Carriers do not usually have symptoms of McArdle disease Different scenarios for the inheritance of McArdle disease are discussed in more detail in this Chapter The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 33

3 1 Genes messenger RNA and protein 3 1 1 Genes are used to make messenger RNA which is used to make protein Although this may seem complicated a basic understanding of genes messenger RNA mRNA and protein is important to understand how mutations in the PYGM gene lead to McArdle disease Proteins are essential within the body They help to make up the structure of the body and control most of the processes of the body The body is able to use genetic information to make almost all the protein it requires Each gene contains the genetic information the genetic code which the body can use to produce a particular protein The PYGM gene encodes the genetic information for the cell to make muscle glycogen phosphorylase Muscle glycogen phosphorylase is an enzyme An enzyme is a special kind of protein which is able to change one thing to another For example muscle glycogen phosphorylase is able to change glycogen into glucose 1 phosphate Glucose 1 phosphate is then broken down by several other enzymes eventually producing glucose Genes are made up of DNA sequences DNA is made up of chemical compounds called nucleotides There are four nucleotides in DNA which are cytosine C thymine T and guanine G and adenine A Different genes each have a unique order or sequence of nucleotides It is possible to use special techniques and machinery a process known as genetic sequencing to determine the nucleotide DNA sequence In the PYGM gene the genetic information which encodes muscle glycogen phosphorylase is made up of 2 523 nucleotides Burke et al 1987 Kubisch et al 1998 DiMauro et al 2002 The DNA sequence of the PYGM gene was first published by Burke et al in 1987 Genetic information is contained in chromosomes Chromosomes are basically a string of genes Humans have 23 pairs of chromosomes There are 22 chromosomes which are unrelated to gender these are called autosomes The X and Y chromosomes are the sex chromosomes which determine gender Men have one X and one Y chromosome and women have two X chromosomes The PYGM gene which encodes muscle glycogen phosphorylase is located on chromosome number 11 Chromosome 11 is an autosome this is why McArdle disease is not related to gender and both men and women can have McArdle disease The chromosomes are located within the nucleus of cells a special compartment in the cell Proteins are made in another area of the cell called the endoplasmic reticulum ER which is basically the protein making factory However the protein making factory ER is located in a different area of the cell to the nucleus As outlined above the gene has the information which the cell needs to make proteins However each gene is contained within a chromosome which is relatively large so the gene cannot be taken outside of the nucleus to the ER In order to solve this problem a temporary copy of the gene is made This copy is called mRNA which stands for messenger RNA The mRNA is a copy of the DNA sequence of the gene which is made in the nucleus The mRNA is very small and is able to move from the nucleus to the ER The mRNA is then used to produce the protein A very simple analogy would be to baking a cake The chromosome is like a cook book with different recipes on each page Each gene is like a recipe You need the recipe at home so that you can bake the cake in your kitchen But the recipe can t be taken away from the library a gene can t leave the nucleus If a photocopy is made of a page with one recipe that is like mRNA You can then take the recipe home and put it in your kitchen mRNA can be transported Page 34 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

from the nucleus to the ER The recipe is used to make a cake in your kitchen at home mRNA is used to make protein in the ER But the photocopy is easily destroyed mRNA does not last long in the cells In the ER the mRNA is translated to produce protein A component of the protein making factory ER called ribosomes makes the protein by joining together amino acids in a long chain Amino acids are the building blocks of proteins The ribosomes use the code in the mRNA to determine in what order to put the amino acids The mRNA is translated in triplets three nucleotides are translated to identify one amino acid These triplets are known as codons For example in muscle glycogen phosphorylase the first three nucleotides ATG encode an amino acid called methionine the single letter code for methionine is M The situation is slightly more complicated than this because the first amino acid is removed from the muscle glycogen phosphorylase protein during the process of making it functional This is discussed further in section 17 5 1 7 There are 20 amino acids which can each be written as a single letter code Each amino acid has a different chemical structure Within the protein amino acids can interact together to make complex structures which are necessary for the protein to function as an enzyme In some proteins including muscle glycogen phosphorylase the order of the amino acids is very important for the protein to be able to function correctly The order of the amino acids is known as a protein sequence or amino acid sequence The protein sequence for muscle glycogen phosphorylase begins MSRPLSDQEKRKQISVRGLAGVENVTE Muscle glycogen phosphorylase is 842 amino acids long Kubisch et al 1998 3 2 Mutations in the PYGM gene prevent production of functional muscle glycogen phosphorylase enzyme and cause McArdle disease McArdle disease is caused by the lack of functional muscle glycogen phosphorylase in muscle cells Almost all known mutations result in a complete lack of functional muscle glycogen phosphorylase It is possible that some mutations may still result in the production of muscle glycogen phosphorylase but that it is not able to fold into the correct shape or to function as an enzyme and therefore it cannot break down glycogen into glucose 1 phosphate There are several types of mutations in the PYGM gene which prevent production of functional muscle glycogen phosphorylase These are illustrated in Table 3 2 and explained more fully below The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 35

e of how different types of mutation disrupt the reading frame using the sentence The cat saw the rat which represents PYGM he person reading the sentence you represents the ribosome which has to decode the mRNA The effect of the mutation upon en The cat s Missense mutation the s is changed to a p The cat paw the rat Frameshift the s is removed deleted The cat awt het at Splice site mutation the space before the s is removed The catsaw the rat Page 36 An example of how each mutation affects the translation of mRNA into protein Kathryn Birch The cat s The cat saw the rat The sentence represents PYGM mRNA The sentence can be read correctly The catsaw the rat Splice site mutation the space before the s is removed Protein has incorrect sequence Protein has incorrect sequence Protein has incorrect sequence Shortened protein is made No protein is made Protein is made correctly Effect on protein production Protein has incorrect s The McArdle Disease Handbook Version 1 1 1 Page 36 Kathryn Birch The McArdle Disease Handbook Version 1 1 1 Table 3 1 An example of how different types of mutation disrupt the reading frame using the sentence The cat saw the rat which represents PYGM mRNA with the triplet codons The person reading the sentence you represents the ribosome which has to decode the mRNA The effect of the mutation upon protein production is also given The cat awt het at Frameshift the s is removed deleted The cat saw the rat The cat paw the rat The sentence represents PYGM mRNA Missense mutation the s is changed to a p Premature stop codon a full stop is introduced between s and a Premature stop codon leads to nonsense mediated decay of the mRNA no sentence is seen Premature stop codon a full stop is introduced between s and a Mutations The sentence can be read correctly Premature stop codon leads to nonsense mediated decay of the mRNA no sentence is seen Correct PYGM mRNA with no mutation Type of mutation NA with no An example of how each mutation affects the translation of mRNA into protein Effect on protein prod Protein is made correc No protein is made Shortened protein is m Protein has incorrect s Protein has incorrect s

duction ctly 3 2 1 Stop codons Stop codons occur naturally at the end of the gene and during translation of mRNA signal to the ribosome that it has got to the end of the instructions to make a particular protein However mutations which introduce stop codons in the wrong place for example halfway through a gene interrupt the instructions Mutations which introduce stop codons in the wrong place are also known as premature stop codons premature termination codons nonsense mutations or nonsense codons In a protein sequence stop codons are indicated by an X An example of how this would be written in a protein sequence would be R50X 50 indicates that it is amino acid number 50 in the protein sequence arginine single letter code R is the original amino acid which has been replaced by a premature stop codon as are shown by X Mutations which introduce premature stop codons can have several effects nonsense mediated decay of mRNA or production of a non functional protein 3 2 1 1 Nonsense mediated decay destroys mRNA containing some premature stop codons Some premature stop codons make the mRNA highly susceptible to being destroyed before it can be used to make a protein mRNA which has a premature stop codon could lead to production of a protein which is too short The body has a surveillance system in place to identify mRNA which has mutations mRNAs containing certain premature stop codons are specifically identified and then destroyed by a process called nonsense mediated decay It has been suggested that the benefit of nonsense mediated decay is to prevent the production of proteins which could potentially be bad for the cell due to the mutations they encode Frischmeyer and Dietz 1999 For example proteins with an incorrect sequence or which are too short may not fold correctly and may instead clump together and stop the cell working properly Several premature stop mutations are known to cause nonsense mediated decay in mRNA encoding muscle glycogen phosphorylase in McArdle people Experimentally if nonsense mediated decay is taking place than it is possible to identify a premature stop codon mutation in the gene genomic DNA but no mRNA will be detected To date August 2011 nonsense mediated decay has been made shown to occur to PYGM mRNA with the premature stop codon mutations R50X L5VfsX22 Q73HfsX7 E125X N134KfsX161 W388_V390delinsSfsX33 R491AfsX7 and D534VfsX4 Bartram et al 1993 Nogales Gadea et al 2008 Sohn et al 2008 Each of these mutations results in no sequence muscle glycogen phosphorylase being made I think that other premature stop codon mutations which lead to nonsense mediated decay will be identified in the future sequence 3 2 1 2 A non functional protein may be made sequence Not all mRNA with mutations is destroyed by nonsense mediated decay The body is not always able to recognise mutations If the body does not identify a mutation then mRNA which contains a mutation is produced in the nucleus and transported to the ER where it is used to make protein M mRNA with However the protein will not have the correct sequence as it will contain the mutation If the protein mutation was a stop codon the protein will be too short Both ends of the muscle glycogen phosphorylase amino acid sequence are very important for muscle glycogen phosphorylase to form the correct shape and be functional It is not functional if the protein is too short because of a premature stop codon For example at present the premature stop codon nearest the end of the PYGM gene is C784X Rubio et al 2007 Muscle glycogen phosphorylase is 842 amino acids long so The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 37

the C784X mutation results in a protein which is missing 58 amino acids It is therefore missing approximately 1 14th of the protein Removing this number of amino acids stops muscle glycogen phosphorylase being functional 3 2 2 Missense mutations Missense mutations change the code of the gene so that the code for one amino acid is replaced by the code for a different amino acid The ribosome will not know that a missense mutation is present in the mRNA and will include the wrong amino acid in the protein Some proteins are able to function even if the wrong amino acid is present but others are not able to function Missense mutations which result in the wrong amino acid being included in the protein can make the protein form the wrong shape or misfold In some cases the cell will recognise that the protein is the wrong shape and will destroy it As of August 2011 61 missense mutations have been identified which prevent muscle glycogen phosphorylase from being able to function Table 3 2 An example of how a missense mutation would be written in a protein sequence would be G205S where 205 indicates that it is amino acid number 205 in the sequence the numbers start at 1 that G single letter code for glycine was the original amino acid and S single letter code for serine indicates that the missense mutation has changed the DNA sequence so that it now encodes serine 3 2 3 Frameshift mutations Frameshift mutations occur if nucleotides are added to or removed deleted from the gene which causes the ribosome to misread the amino acid sequence specified by the mRNA Misreading of the amino acid sequence leads to the production of a protein which doesn t have the right sequence of amino acids and is not able to function in the normal way Frameshift mutations change the way in which the ribosome reads the amino acids sequence and often this results in a premature stop codon An example of how this would be written would be L5VfsX22 This indicates that amino acid number 5 was originally L single letter code for Leucine and fs indicates that a frameshift mutation has now occurred 22 means that after misreading 22 amino acids a premature stop codon shown by X has been introduced 3 2 4 Splice site mutations Genes are slightly more complicated than already described Basically genes are composed of coding regions called exons which are used to make mRNA and encode the sequence for making proteins and non coding regions called introns which are not used to make protein During the process of making mRNA mRNA is first made which includes both the exons and introns However splicing then takes place During splicing introns in the mRNA are removed The exons are then joined together at splice sites It is possible to have a mutation at the splice site This can disrupt the removal of introns or prevent the joining of exons so that the mRNA sequence is no longer correct It will therefore not be possible to use this mRNA to produce functional protein Splice site mutations can cause McArdle disease Fernandez Cadenas et al 2003 described a McArdle person with a splice site mutation K608K in the muscle glycogen phosphorylase gene When the mRNA was studied closely it was shown that this mutation caused major changes the way in which the mRNA was spliced and was read by the ribosome Garcia Consuegra et al 2009 identified a nucleotide change c 529 8 g a in the splice sequence of intron 4 which caused retention Page 38 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

of 6 nucleotides in the coding region of intron 4 which would lead to the insertion of two amino acids in the coding region However there are a few very rare cases where mutations in splice sites still result in production of a very low level of functional enzyme see section 9 1 3 3 2 5 Theoretical possible outcomes of various mutations There remains a lack of published data on whether having a specific mutation has an effect on whether the mRNA can be detected and if there is any muscle glycogen phosphorylase present Different amounts of muscle glycogen phosphorylase mRNA and protein have been reported by researchers but in many cases the specific mutation was not known The flowchart shown in Figure 3 1 is my own theoretical explanation of what may cause the different amounts of mRNA and protein which have been reported in published papers Figure 3 1 Flowchart illustrating theoretical explanations for the possible effects of different mutations in the PYGM gene upon stability of mRNA and production of protein Wright 2009 PYGM mRNA containing a premature stop codon may be subject to nonsense mediated decay and degraded preventing translation of the amino acid sequence If mRNA with a premature stop codon is not subject to nonsense mediated decay the protein may be stable and detectable or it may be unstable and quickly destroyed by the cell Other mutations such as missense splice site insertion inversion or deletion mutations are likely to lead to detectable stable mRNA unless they introduce a premature stop codon which causes nonsense mediated decay These mRNAs may result in either The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 39

stable detectable protein being produced or unstable protein which is quickly broken down by the cell Mechanisms to identify and destroy incorrect proteins are known as protein degradation pathways The variable outcomes illustrated in Figure 3 1 have been demonstrated by studies of muscle glycogen phosphorylase from McArdle people Normal levels reduced levels or a complete absence of muscle glycogen phosphorylase protein have been reported in McArdle people although in all these cases the protein is non functional 3 2 6 How many of these mutations have been identified in the PYGM gene so far Currently 137 mutations in the PYGM gene have been found which cause McArdle disease reviewed in Wright 2009 Mutations found in the PYGM gene have included missense premature stop codons splice site insertion inversion and single base deletions summarised in Table 3 2 These are located throughout the muscle glycogen phosphorylase amino acid sequence rather than just occurring in particular areas of the gene 3 2 6 1 Most of the mutations are specific to particular ethnic groups The locations of the mutations within the PYGM gene depend on the ethnic background of the person The most common mutation amongst Caucasians in Europe and North America is the R50X mutation in exon 1 DiMauro et al 2002 This occurs when an arginine CGA is mutated to the premature stop codon mutation TGA The R50X mutation is the cause of McArdle disease in 81 of British McArdle people between 63 DiMauro et al 2002 and 75 Tsujino et al 1995 of US McArdle people 56 of German McArdle people and 32 of Italian and Spanish McArdle people DiMauro et al 2002 Quintans et al 2004 Type of mutation Loss of start site Premature stop codon of which known to be subject to nonsense mediated decay Missense Deletion of one or more amino acid s of which deletion of a single amino acid Splice site or intronic mutations Silent polymorphism Insertion deletion Frameshift of which resulting in a premature stop codon known to be subject to nonsense mediated decay Total number of mutations identified to date Number of locations identified to date for mutation within PYGM gene 2 15 2 61 6 5 20 3 3 27 13 6 137 Table 3 2 Summary of mutations in the coding sequence and splice sites of the human PYGM gene known to cause McArdle disease correct as of August 2011 Page 40 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Other mutations appear to be specific to ethnic groups For example the single codon deletion 708 709 has only been found in Japan Other ethnic mutations include R270X and R602Q which were found in two unrelated Yemenite Jewish families Hadjigeorgiou et al 2002 Until recently no McArdle people had been identified in some ethnic groups Quinlivan et al 2010 recently described a Pakistani McArdle person where both copies of the PYGM gene had a newly discovered single base pair deletion in exon 1 c 14delT which resulted in a premature stop codon pL5RfsX20 A Korean person who had a novel single codon deletion p779delE plus the R50X mutation was described by Sohn et al 2008 Several cases of people where McArdle disease was caused by both copies of the PYGM gene having the V456M mutation in exon 11 have been described this mutation was found in a Moroccan baby Mancuso et al 2003 in a Latin American person born in Ecuador Fernandez Cadenas et al 2007 and in people from Tunisia and Algeria Aquaron et al 2007 3 2 7 What caused the first mutation in the PYGM gene It is not known what caused the first mutation in the PYGM gene The body has to copy all the DNA including the PYGM gene to produce egg and sperm cells If this copying process introduces an error into the PYGM gene in an egg or sperm cell which is then used to conceive a baby the mutation in the PYGM gene will also be inherited Mutations occur relatively frequently in the human genome but often have no effect or mild effect In general natural selection removes mutations which have a lethal effect but recessive mutations often remain at low frequency in populations It is highly likely that mutations in the PYGM gene and McArdle disease have been occurring for throusands of years long before Dr Brian McArdle published his paper describing the condition in 1951 3 3 How is McArdle disease inherited 3 3 1 One copy of each gene is inherited from each parent During conception each person will inherit one set of chromosomes from their mother and one set of chromosomes from their father They will inherit a copy of the PYGM gene from each parent giving a total of two copies of the PYGM gene in each person To continue the analogy to baking a cake with a cook book which was used earlier section 3 1 1 each person will have one set of books from their mother and one set from their father Both the chromosome book from the mother and chromosome book from the father will have a gene recipe e g the PYGM gene for each protein e g muscle glycogen phosphorylase So each person will have two copies of the gene PYGM which contains the genetic information for muscle glycogen phosphorylase 3 3 2 What are the combinations of normal and faulty copies of the PYGM gene which can occur People unaffected by McArdle s have two normal copies of the PYGM gene The normal copy of the PYGM gene is used to produce functional muscle glycogen phosphorylase which works normally in muscle The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 41

Carriers have one normal copy of the PYGM gene and one faulty copy of the PYGM gene They do not usually have symptoms of McArdle disease see section 9 1 1 The faulty copy of the PYGM gene cannot produce any functional muscle glycogen phosphorylase but the normal copy of the PYGM gene is able to produce functional muscle glycogen phosphorylase Carriers have approximately half the amount of functional muscle glycogen phosphorylase compared to people unaffected by McArdle disease see section 9 1 1 and this is enough enzyme to allow the muscle to work normally McArdle people have mutations in both their copies of the PYGM gene These mutations may be different in each copy of the PYGM gene Neither of the mutant copies of the PYGM gene can be used to produce functional muscle glycogen phosphorylase for rare exceptions see section 9 1 3 McArdle people do not have any functional muscle glycogen phosphorylase in their muscles and therefore have McArdle disease 3 3 3 Methods of inheritance 3 3 3 1 Recessive disease versus dominant disease McArdle disease is a recessive disease which means that a person must inherit two faulty copies of the PYGM gene in order to have McArdle disease In the case of a recessive disease carriers do not have any symptoms of the disease as they have one normal copy and one faulty copy of the gene In a dominant disease carriers do have symptoms Just one faulty copy of the gene is sufficient to have all the symptoms of the disease even though the carrier has one normal copy of the gene An example of a dominant disease is malignant hyperthermia which is discussed further in section 12 3 1 Although there has been at least one paper suggesting that McArdle s had been inherited in a dominant or pseudo dominant way this was incorrect and was due to the combination of an asymptomatic carrier parent with a McArdle parent who had both the R50X and a novel mutation which was not discovered until later Tsujino et al 1993 Isackson et al 2005 3 3 3 2 Autosomal disease versus sex linked disease McArdle disease is an autosomal disease This means that inheritance is unrelated to gender and men and women are equally likely to have McArdle s Sex linked inherited diseases usually occur due to a mutation in a gene which is located on the X chromosome If the disease is sex linked and recessive women are much less likely to have the disease as they have two X chromosomes Even if the faulty copy of the gene is located on one of their X chromosomes they are likely to have a normal copy of the gene on their other X chromosome Men only have one X chromosome so if they have a mutation in a gene on that chromosome they have no back up gene on their second X chromosome Men are much more likely to have sex linked inherited diseases than women Haemophilia is an example of a sex linked recessive disease where men are affected much more frequently than women 3 3 3 3 Genetics nomenclature In the following examples upper case M is used to represent the normal copy of the PYGM gene for muscle glycogen phosphorylase Lower case m is used to represent the faulty copy of the Page 42 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

PYGM gene There is no standard one letter code used to represent PYGM so I have chosen to use the letter m However the use of upper and lower case as described above is standard practice in genetics Information about a person s genotype information about which copies of the PYGM gene they have can therefore be written as follows A McArdle person would be written as mm A carrier would be written Mm A person unaffected by McArdle s would be written MM Humans have two copies of the PYGM gene A baby will inherit one copy from the mother and one copy from the father This is achieved because during the production of egg and sperm known as gametes in the parents only one of the two copies of the PYGM gene go into each The actual mechanism for egg and sperm production is a little more complicated than this and involves a few extra steps before this part but this is the important part and is sufficient to understand inheritance If the parent is unaffected by McArdle s MM the gametes will be either M or M so the child can only inherit M If the parent is a carrier Mm the child could inherit either M or m If the parent has McArdle s mm the child could only inherit m When the parents have a baby the possible outcomes can be illustrated by a diagram known as a Punnet square invented by Mr Punnet The chances for each subsequent child are exactly the same and are not altered by whether any previous child had McArdle s was a carrier or was unaffected 3 3 4 How many people have McArdle disease or are carriers of a mutation in PYGM McArdle disease is a rare disease It has been estimated that the frequency of people with McArdle disease is approximately 1 in 100 000 Applegarth et al 2000 Haller 2000 Tarnopolsky 2006 Beynon et al 2002 The number of people who are carriers is also low It has been suggested that the number of people who are carriers for McArdle disease is between 1 in 66 Tarnopolsky 2006 and 1 in 158 Isackson et al 2005 Examples of how McArdle disease is inherited are outlined below Because McArdle disease is so rare a McArdle person or a carrier is most likely to have a partner who is unaffected by McArdle s For completeness several different scenarios are described 3 3 5 Examples of how McArdle s is inherited As McArdle s is inherited in an autosomal manner the possible outcomes are unaffected by whether the parent with McArdle s is the mother or father Please assume that parents are not related in the following examples A different pattern of inheritance might be seen if the parents were closely related which is explained further in section 3 3 6 The examples show the chances of having a child with McArdle s depending upon whether the parents were unaffected carriers or have McArdle disease themselves For a pair of parents the likelihood of a child having McArdle s is exactly the same for the every subsequent child as the first child For example in the case of a carrier parent plus a carrier parent as illustrated in Table 3 1 the first child has a 25 chance of having McArdle s If the same parents have a second child this child will also have a 25 chance of having McArdle s All subsequent children will each have a 25 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 43

chance of having McArdle s Some families may have no children with McArdle s some families may have some children with McArdle s and some unaffected children and yet other families may have all children with McArdle s but in each case the risks were the same NOTE The following information is based upon theoretical methods of inheritance It is not intended to replace genetic counselling Medical advice genetic counselling should be sought if you would like to discuss or further understand the way in which McArdle s is inherited or the chances of having a child with McArdle s 3 3 5 1 Neither of my parents had symptoms of McArdle s but I have McArdle s It is likely that both parents were carriers each parent had one normal copy of the PYGM gene and one faulty copy of the PYGM gene Carriers of the faulty copy of the PYGM gene do not usually have symptoms of McArdle disease In order for the child to have McArdle s the child must have inherited a faulty copy of the PYGM gene from each parent resulting in two faulty copies of the PYGM gene and no normal copies Carrier parent Mm plus carrier parent Mm If both parents are carriers there is a 25 1 out of 4 chance that the child will be unaffected a 50 2 out of 4 chance that the child will be a carrier and a 25 1 out of 4 chance that the child will have McArdle s Father Mm carrier Sperm cells have M m Mother Mm carrier Egg cells have M MM unaffected Mm carrier M Mm carrier mm McArdle s Figure 3 2 A punnet square illustrating the possible outcomes when a father who is a carrier Mm has a baby with a mother who is also a carrier Mm There is a 25 1 out of 4 chance that the child will be unaffected MM a 50 2 out of 4 chance that the child will be a carrier Mm and a 25 1 out of 4 chance that the child will have McArdle s mm 3 3 5 2 I have McArdle disease and my partner does not will my children have McArdle disease The parent with McArdle disease will be homozygote for the mutation w ill have two faulty copies of the PYGM gene There are two possible situations for the partner The partner could be unaffected have two normal copies of the PYGM gene or could be a carrier McArdle s parent mm plus unaffected parent MM The only possible outcome is that the child is a carrier Mm There is a 4 out of 4 100 possibility that the child will be a carrier This is the most commonly occurring situation and results in a child which is a carrier and does not have any symptoms of McArdle s Page 44 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Father mm McArdle s Sperm cells have M m Mother MM unaffected has two normal copies of the PYGM gene Egg cells have M Mm carrier Mm carrier M Mm carrier Mm carrier Figure 3 3 A punnet square illustrating the possible outcomes when a father who has McArdle s mm has a baby with a mother who is unaffected MM The only possible outcome is that the child is a carrier Mm There is a 100 4 out of 4 chance that the child will be a carrier McArdle s parent mm plus carrier parent Mm There is a 2 out of 4 50 chance that the child will be a carrier and a 2 out of 4 50 chance that the child will have McArdle s None would avoid receiving at least one faulty copy of the PYGM gene There is a 50 chance that both the parent the father in this example and the child will have McArdle s This can be the explanation when McArdle s appears to run in families and to be passed down the generations This doesn t happen very often because McArdle s is relatively rare Father mm McArdle s Sperm cells have m m Mother Mm carrier Egg cells have M Mm carrier Mm carrier M mm McArdle s mm McArdle s Figure 3 4 A punnet square illustrating the possible outcomes when a father who has McArdle s mm has a baby with a mother who is a carrier Mm There is a 50 2 out of 4 chance that the child will be a carrier Mm and a 50 2 out of 4 chance that the child will have McArdle s mm 3 3 5 3 My partner and I both have McArdle s This is a very unusual situation but is included for completeness If both parents have McArdle s they must both be homozygous for the mutation must have two faulty copies of the PYGM gene McArdle s parent mm plus McArdle s parent mm There is a 4 out of 4 100 chance that the child will have McArdle s The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 45

Father mm McArdle s Sperm cells have m m Mother mm McArdle s Egg cells have M mm McArdle s mm McArdle s M mm McArdle s mm McArdle s Figure 3 5 A punnet square illustrating the possible outcomes when a father who has McArdle s mm has a baby with a mother who also has McArdle s mm There is a 100 4 out of 4 chance that the child will have McArdle s mm 3 3 5 4 I am a carrier of McArdle disease Will my children have McArdle disease The answer depends on whether your partner has any faulty copies of the PYGM gene A person who is a carrier could have a partner who either a has McArdle s see Figure 3 4 b is a carrier see Figure 3 2 c is unaffected see below Carrier parent Mm plus unaffected parent MM There is a 2 out of 4 50 chance that the child will be unaffected and a 2 out of 4 50 chance that the child be a carrier Father MM unaffected Sperm cells have M M Mother Mm carrier Egg cells have M MM unaffected MM unaffected M Mm carrier Mm carrier Figure 3 6 A punnet square illustrating the possible outcomes when a father who has is unaffected MM has a baby with a mother who is a carrier Mm There is a 50 2 out of 4 chance that the child will be unaffected MM and a 50 2 out of 4 chance that the child be a carrier Mm 3 3 5 5 My grandmother grandfather aunt uncle has McArdle disease Having a grandparent or aunt uncle with McArdle s may suggest that you could be a carrier It will not be possible to determine this without a genetic test or possibly a muscle biopsy to accurately quantify the amount of muscle glycogen phosphorylase as carriers usually have approximately half the amount of muscle glycogen phosphorylase compared to unaffected people Unless family members have had children together the chances of a carrier having a partner who is also a carrier is relatively unlikely It is therefore unlikely that you would have a child which has McArdle s For Page 46 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

this reason I suspect that many family doctors would not be interested in performing tests to determine if you are a carrier 3 3 6 Consanguineous parents why are they more likely to produce a child with an inherited disease Consanguineous means that the parents are closely related family members Examples of this could be two siblings or first cousins having children together There are many different recessive diseases which a parent could have but if a child has unrelated parents it is unlikely that both parents will be carriers of a faulty copy of the same gene If the child inherits only one faulty copy of a gene it will be a carrier and will usually not have any symptoms In contrast siblings or cousins are more likely to be carriers of a faulty copy of the gene for the same recessive disease or even for faulty copies of genes for several different recessive diseases This may result in their child having one or multiple inherited diseases Mancuso et al 2003 reported a consanguineous marriage which resulted in the birth of a baby that had McArdle disease and also mitochondrial DNA depletion syndrome see section 8 1 1 These are both autosomal recessive diseases It is likely that both parents were carriers for both of these diseases and the child inherited several diseases Recommended reading Basic Genetics Textbook and Activities By Ahmed Abouelmagd Hussein M Ageely Google free books For general information about inheritance There are many other complicated patterns of inheritance so focus on autosomal recessive inheritance The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 47

Page 48 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

4 Exercise muscle contractions and contractures muscle cramps Anaerobic exercise is when a short burst of high intensity exercise occurs for example running for a bus For McArdle people more than a few seconds of this type of intense exercise can cause muscle damage and lead to muscle cramps contractures For McArdle people the saying No pain no gain does NOT apply If pain is felt then McArdle people should stop exercising and rest However after a rest energy is provided to the muscles from a different source This creates a second wind which enables McArdle people to exercise further More effort is required to move around a heavier body so McArdle people are recommended to maintain a healthy weight and avoid being overweight Muscle contractures are painful muscle cramps which can last several hours or days At present the scientific reason for this pain is not known The only recommended treatment for contractures is rest McArdle people have anecdotally reported the following home treatments use of cool ice packs heat packs strong painkillers and massage There is no published information on any of these home treatments and some of these treatments like massage could lead to further damage to the muscles Pain can serve as a warning to protect the muscle from further damage so McArdle people should be warned that the use of strong painkillers could lead to the muscle being used which could cause further damage The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 49

4 1 Types of exercise Exercise can basically be divided into two classes aerobic and anaerobic 4 1 1 Anaerobic exercise Anaerobic exercise occurs when energy is produced in the muscle cells without using oxygen This occurs when the blood is not able to supply enough oxygen to the muscle cells for aerobic exercise to occur Sleamaker and Browning 1996 Anaerobic exercise is usually when a short burst of high intensity exercise occurs An example of this would be fast sprinting like running for a bus The energy for muscle cells to move during exercise is usually provided by a combination of aerobic and anaerobic exercise However the first 10 to 30 seconds of exercise are solely anaerobic Sleamaker and Browning 1996 Initially free glucose in the muscle cells is used to provide energy for movement However this is used up within the first few minutes of exercise In people unaffected by McArdle s energy is then produced by glycogenolysis This is the chemical reaction where stored glycogen is broken down to produce glucose which is used to generate Adenosine Triphosphate ATP Muscle glycogen phosphorylase is essential for this chemical reaction in muscle cells Because muscle glycogen phosphorylase is not functional McArdle people cannot utilise this energy source 4 1 2 Aerobic exercise Aerobic exercise takes place when oxygen is supplied in the bloodstream to the muscles Taking a breath of air pulls the air into the lungs The lungs are made up of lots of alveoli which are tiny sacks The surfaces of the alveoli are covered in lots of blood vessels Oxygen from the air binds to haemoglobin in the red blood cells Haemoglobin with oxygen bound to it is then pumped around the body to many places including the muscles In the muscles oxygen is taken from the haemoglobin in the blood vessels into the muscle cells The oxygen is then combined with sources of energy such as free fatty acids in chemical reactions which generate ATP energy Aerobic exercise is defined as exercise for a minimum of ten minutes Sleamaker 1996 An example of aerobic exercise would be walking on a road or treadmill for 20 minutes 4 2 Exercise recommendations for McArdle people 4 2 1 Anaerobic exercise or static muscle contractions should be avoided Strenuous exercise must be avoided as it can lead to muscle damage muscle cell breakdown and possible kidney failure Lucia et al 2008a recommend McArdle people to avoid exercise that induces severe pain and in particular to avoid static muscle contractions Static muscle contractions also called isometric contractions are those which are required to hold something in one place for a long time such as holding the body in one place for a long time by squatting or holding a heavy bag or weight for a long time Andrew Wakelin McArdle s Coordinator for AGSD UK suggests a six second rule see Box 4 1 This suggestion is based upon the experiences of McArdle people but has not been scientifically proven Page 50 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

The six second rule To avoid damage when doing something of maximum intensity it is a good idea to time 6 seconds by saying to One thousand two thousand up to six If the task is not completed by 6 stop or put it down Take a break let the muscles recover and try again later Box 4 1 The six second rule as suggested by Andrew Wakelin Taken from www agsd org uk 4 2 2 Moderate aerobic exercise and conditioning improves symptoms of McArdle s The breakdown of fatty acids and amino acids and the release of glucose from the liver provide the energy for the second wind In the second wind energy is produce using oxygen for oxidative phosphorylation and is therefore aerobic McArdle people are able to continue to exercise aerobically for a long period of time using fatty acid oxidation to provide energy Quinlivan and Vissing 2007 Exercising regularly but gently improves aerobic conditioning Aerobic conditioning is the ability of the lungs to take in more oxygen and the ability of the heart to pump blood round the body Aerobic conditioning improves the supply of glucose fatty acids and oxygen to the muscles via the bloodstream and also improves the ability of the mitochondria to utilise sources of energy Vissing and Haller 2003 Quinlivan and Vissing 2007 Quinlivan et al 2008 Warming up prior to exercise will improve blood supply to the muscles and can aid the transition to second wind Haller 2000 Low level warm up Amato 2003 and regular light aerobic exercise can speed the beneficial transition to second wind from anaerobic to fatty acid oxidation in McArdle people Quinlivan et al 2008 Perez et al 2008 described a 9 year old boy with McArdle disease who presented with severe myalgia muscle pain muscle weakness myoglobinuria and elevated creatine kinase after exercise He was recommended to consume 20g of carbohydrate before exercise and to carry out age appropriate exercise One year later his fitness had improved he was able to exercise and perform ordinary activities and had almost normal serum creatine kinase levels He had not had any further acute clinical episodes such as myoglobinuria Haller et al 2006 investigated whether aerobic conditioning regular aerobic exercise could improve the ability of McArdle people to exercise The training programme for eight McArdle people was as follows they were trained on a cycle ergometer for 30 40 minutes four days a week for 14 weeks They exercised at an intermediate rate not the hardest they could do The authors found that after this period of training the participants were able to carry out more exercise take in more oxygen which is needed to produce energy during the second wind and their heart was able to pump blood more efficiently They also found that levels of some of the enzymes involved in producing energy called citrate synthase and hydroxyacyl coenzyme A dehydrogenase had increased The participants did not have pain cramps and the level of creatine kinase in the blood did not rise during the exercise which suggested that the exercise was not causing muscle damage The participants were still able to achieve a second wind in the same way as before the training programme The authors concluded that moderate aerobic exercise was a way to increase the ability of McArdle people to exercise The training programme improved the ability of the heart to pump blood around the body which increased the amount of energy sources which could be taken by the blood to the muscles The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 51

Other researchers have also described positive results of aerobic training for McArdle people Quinlivan and Vissing 2007 describe unpublished data by Portero et al Portero et al carried out a trial where four McArdle people performed aerobic exercise for 30 45 minutes three times a week for eight weeks The authors said that the results showed an improvement in the amount of oxygen taken into the body an increase in the amount of glucose carried in the blood to the muscle cells and increase in the ability to exercise and the length of time which exercise could be carried out and also a reduction in the CK levels in the blood Quinlivan and Vissing 2007 also describe an unpublished study by Zange et al who studied two McArdle people who carried out aerobic training daily for 12 weeks Following the training programme these McArdle people also had an improvement in strength without any significant adverse effects There were no episodes of pain or cramping 4 2 3 Being overweight can make McArdle people find it harder to move around A large number of McArdle people are overweight Quinlivan et al 2010 reported that 71 32 of 45 of the McArdle people seen at the UK McArdle Clinic were clinically overweight with a body mass index BMI greater than 26 This is not surprising when you remember that in the past McArdle people were advised to avoid exercise And also that in the past McArdle people were advised to have a sugary drink before exercise If a sedentary lifestyle is combined with consuming a lot of sugar it is likely to lead to weight gain The advice to McArdle people is now different moderate exercise is recommended see section 4 2 2 and although a sugary drink can be of use in certain circumstances it obviously has to be used in moderation see section 7 1 6 2 McArdle s experts are now keen to ensure McArdle people are warned about this disadvantage of a sugary drink When informing people with McArdle disease about such treatment sugary drinks before exercise family doctors should stress the importance of restricting its use to avoid unintentional weight gain Vissing and Haller 2003 For people unaffected by McArdle disease the ways in which they can maintain a healthy weight include a balanced diet and regular exercise For McArdle people there is some debate about what the balance of carbohydrate and protein in the diet should be see section6 6 but it remains the case that if you consume more calories more food or energy than you use then this will result in weight gain Energy from food is used up in everyday life walking around or doing housework in addition to during exercise For anybody whether they have McArdle s or not being overweight leads to an increased risk of other serious health problems such as heart disease and cancers of the breast colon and prostate source http www nhs uk Livewell loseweight Pages Whyyourweightmatters aspx In addition to these risks a disadvantage of being overweight for a McArdle person is that it may make it harder to exercise Amato 2003 A heavier body weight increases the amount of work which the muscles have to do in holding the body upright and in moving around This is more likely to lead to muscle damage rhabdomyolysis and muscle pain if the muscles are unfit or unconditioned 4 3 Muscle contraction and relaxation A very simplified description of a muscle cell is that it is like a bag of liquid The liquid is called the cytoplasm or sarcoplasm Inside this bag are small compartments one of which is the sarcoplasmic reticulum SR The sarcoplasm has a very high concentration of potassium and the SR has a high Page 52 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

concentration of sodium The sodium has a very important role as it is used to transmit a nerve impulse to stimulate muscle contraction Muscle contractions are stimulated by nerve cells The area where a nerve meets a muscle is called the neuromuscular junction In order for a muscle to contract a compound called acetylcholine is released from the nerve This passes through the neuromuscular junction and binds to the end of the muscle When acetylcholine binds to the muscle it opens special channels which let sodium move from the SR into the sarcoplasm and allow potassium to move in the opposite direction As the amount of sodium begins to increase in the sarcoplasm adjacent channels begin to open causing a ripple effect along the length of the muscle cell The amount of sodium within the sarcoplasm quickly increases This triggers calcium channels release of calcium from the SR into the sarcoplasm where the calcium binds to troponin a component of muscle The presence of calcium binding to troponin stimulates the myosin and actin two main proteins in muscle to pull against each other causing muscle contraction Energy in the form of ATP is also required for myosin and actin to create a muscle contraction A muscle contraction occurs when there is a high concentration of sodium within the sarcoplasm and a high concentration of potassium in the SR If further acetylcholine was released from the nerve there would be no sodium available to flow through the special channels into the sarcoplasm Calcium could not be released and the muscle would not be able to contract In order to prepare the muscle so that it is ready to contract again the sodium must be returned to the SR and the potassium must be returned to the sarcoplasm There is a sodium potassium pump and also a calcium pump in the muscle cell The sodium potassium ATPase pump uses ATP to provide the energy to move sodium to the sarcoplasmic reticulum and potassium into the sarcoplasm In addition to enabling the transmission of nerve impulses the sodium potassium ATPase pump also maintains a high concentration of sodium in the SR which keeps the right amount of water within the cell If the sodium stopped being pumped out water could move into the cell by a process called osmosis and this could cause the cells to swell After a muscle contraction has occurred the calcium ATPase pumps use ATP to provide the energy to pump calcium from the sarcoplasm to the SR This removes calcium from the troponin which results in relaxation of the muscles Martonosi 2000 In people unaffected by McArdle s the calcium is all pumped back into the sarcoplasmic reticulum within 30 milliseconds causing the muscles to relax Alberts et al 1994 4 3 1 Muscles require energy ATP to contract and to relax during exercise Muscle contractions require energy Food is the inital source of energy Food is digested in the digestive system then transported in the blood to the muscle cells where it is further broken down by several different mechanisms to release energy as ATP The muscle cells require ATP to contract Muscle contractions are needed to carry out all forms of exercise However in McArdle people the lack of muscle glycogen phosphorylase means that muscles are not able to use ATP produced from the breakdown of glycogen into glucose Within muscle cells and other cells in the body energy is stored in bonds between adenosine and phosphates Up to three phosphates can be attached to adenosine and the names of the The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 53

compound will change accordingly see Table 4 1 When the bond between a phosphate and the adenosine is broken energy is released For example adenosine triphosphate ATP is converted into phosphate denoted as Pi and adenosine diphosphate ADP releasing energy This release of energy can be used for many purposes including driving a calcium pump as described in paragraph 4 4 1 Number of phosphates attached to adenosine Name of the structure 1 Adenosine monophosphate AMP 2 Adenosine diphosphate ADP 3 Adenosine triphosphate ATP Table 4 1 Names of the structure depends on how many phosphates are bound In order to function the calcium pumps and the sodium potassium pumps require ATP Glucose within the muscle cells is used to produce ATP Muscle cells contain a small amount of glucose which is rapidly used up during intense exercise Glycolysis is the process where muscle glycogen phosphorylase and other enzymes convert glycogen stored in the muscle cells into glucose which is used to produce ATP In people unaffected by McArdle s it has been estimated that about 20 of the ATP used by a muscle cell during exercise is produced by glycolysis Conley et al 2001 In McArdle people this ATP cannot be made and it would be expected the cells would temporarily run out of ATP during exercise Once the second wind occurs the muscle cells can receive glucose from the liver and fats in the bloodstream both of which can be used to produce ATP 4 3 2 Muscle contraction and relaxation in McArdle people Most of the published studies have looked at the effect of excessive exercise upon the muscle of McArdle people I was not able to find any studies which looked at the ATPase pumps or calcium sodium and potassium within the muscles of McArdle people who are exercising for only a short period of time or aerobically I think that the assumption is that when McArdle people are exercising aerobically muscle contraction and relaxation is basically the same as in people unaffected by McArdle s 4 4 Muscle pain can occur if McArdle people exercise anaerobically It is not known why intense exercise causes pain for McArdle people For people unaffected by McArdle s one theory is that lactic acid lactate produced in muscle cells during intense exercise causes pain Lactic acid is produced during glycolysis the process where glycogen is used to produce glucose and then energy The lactic acid makes the cells become more acidic and this stimulates the nerves creating pain sensations McArdle people are unable to produce energy by glycolysis and do not produce lactic acid during exercise A study by Malucelli et al 2005 showed that in McArdle people the pH does not become more acidic and may instead become slightly more alkaline during exercise This suggests that muscle pain in McArdle disease is not caused by lactic Page 54 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

acid Since McArdle people feel pain after intense exercise some scientists claim that this disproves the theory that lactic acid causes muscle pain but at present it is not known whether the cause of muscle pain in McArdle people is the same as in people unaffected by McArdle s 4 4 1 The phrase No pain no gain does NOT apply to McArdle people For people with McArdle s pain is felt in the muscles when the muscle cells run out of energy This pain is a way of the body telling you to stop exercising and rest After a rest energy should then be provided by the second wind and it should then be possible to exercise further Continuing to exercise once pain is felt could lead to muscle damage Lucia et al 2008a describe the severe pain which is felt during exercise as a self protective mechanism and say that if a McArdle person continues to exercise once pain occurs then it could increase the risk of muscle damage myoglobinuria and kidney failure For McArdle people the saying no pain no gain does NOT apply and could have dangerous consequences 4 5 A muscle contracture cramp can occur if McArdle people continue to exercise anaerobically after pain is felt 4 5 1 A contracture is a muscle cramp without nerve electrical signals Muscle contractures cramps are a well known phenomenon in McArdle people following intense exercise Rommel et al 2006 Lucia et al 2008a and many other publications Contractures cause the muscles to go hard to swell up and it becomes very difficult to move or relax the muscle Contractures can occur if the muscles are exercised intensely and if the McArdle person continues to exercise once pain is felt From a medical point of view a contracture is a particular kind of muscle cramp which occurs in the absence of nerve electrical signals which could be detected with an EMG The physiological contractures which occur in McArdle people should not be confused with another unrelated medical condition also called contractures that can occur where connective tissue such as joint capsules or ligaments can gradually change and become shortened The stiffness of physiological contractures experienced by McArdle people are physiologically different to stiffness caused by rheumatic arthritis or old age 4 5 2 What causes muscle contractures The biochemical reason for contractures is still not properly understood Lucia et al 2008a At present the most common theories are that contractures occur when one or both of the sodium potassium ATPase pumps or the calcium ATPase pumps stop working Swift and Brown 1978 studied two McArdle people They used radioactivity to see what happened to the bone and muscle during contractures They found unusual results because the muscles became labelled in a way which suggested that calcium was involved in contractures The authors suggested that either the exercise caused muscle damage which led to accumulation of calcium in the muscles during contracture or that certain small capsules in the muscle cells called sarcoplasmic reticulum were unable to pump the calcium back into them after activity so that the calcium remained in the main part of the cell the cytoplasm sarcoplasm This may be the research that led Quinlivan and Vissing 2007 to say that contracture is caused by inhibition of calcium ATPase The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 55

If the sodium stopped being pumped out water would diffuse into the cell by a process called osmosis and this could cause the cells to swell I wonder if this leads to the swelling of muscle cells observed by McArdle people during contracture but haven t found any published evidence to support this theory ATPase pumps require energy in the form of ATP If there is insufficient ATP the pumps cannot work The pumps can also be inhibited prevented from working by a build up of waste products such as ADP These theories are explained in further detail below 4 5 2 1 Theory one A lack of ATP prevents the ATPase pumps from working During intense exercise free ATP within the muscle cell is quickly used up In people unaffected by McArdle s muscle glycogen phosphorylase converts glycogen into glucose which can then be used to produce ATP In McArdle people the muscle cells are not able to convert glycogen into glucose and are not able to produce ATP In a McArdle person during exercise calcium will flow from the SR into the sarcoplasm of the muscle cell which stimulates a muscle contraction Normally ATP in the muscle cell would then be used to power the calcium ATPase pump which will move calcium from the sarcoplasm into the SR Once the calcium is returned to the SR the muscle cell will be ready to receive a signal from a nerve and generate a contraction However in McArdle people because the muscle glycogen phosphorylase is not functional glycogen cannot be made into glucose This produces a lack of ATP Without ATP the ATPase pump is unable to function At this point in time there is a high concentration of sodium within the sarcoplasm and a high concentration of potassium in the SR If further acetylcholine was released from the nerve there would be no sodium available to flow through the special channels into the sarcoplasm Calcium could not be released and the muscle would not be able to contract It is likely that a lack of ATP would prevent both the sodium potassium ATPase pump and the calcium ATPase pump from working As early as 1968 a research group including Dr Brian McArdle initially suggested that it could be depletion of ATP giving rise to a contracture similar to rigor mortis Gruener et al 1968 Studies by Gruener et al found that there was little or no reduction in the ATP level of muscle in contracture which was later confirmed by Lewis et al 1985 Lewis and Haller 1986 and Lofberg et al 2001 These studies have shown that the levels of ATP in the muscles of McArdle people only decrease slightly during exercise the decrease is similar to that seen in people unaffected by McArdle s suggesting that contractures are not caused in the same way as rigor mortis 4 5 2 2 Theory two The ATPase pumps are inhibited by ADP and Pi An alternative hypothesis is that the compounds produced when ATP is used for energy could stop the ATPase pumps from working When ATP is used to produce energy for muscle contraction it is broken down into Pi and ADP Lewis and Haller 1986 said that exercise would lead to an increased amount of Pi and ADP in muscle cells They state that accumulations of Pi and ADP are known to inhibit the sodium potassium ATPase and the calcium ATPase 4 5 3 McArdle people have fewer sodium potassium pumps Haller et al 1998 found that McArdle people have fewer sodium potassium pumps than people unaffected by McArdle s In a study of six McArdle people Haller et al found that McArdle people had approximately a third fewer sodium potassium pumps As described above the sodium potassium pumps play an essential role in returning sodium to the SR so that the muscle is ready to Page 56 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

contract as soon as it is stimulated by a nerve It is likely that when gentle exercise is performed the sodium potassium pumps of McArdle people are able to function sufficiently to allow muscle contraction to occur However when McArdle people perform intense exercise the pumps may not be able to function fast enough and the muscle will not be able to contract in response to a signal from the nerve Even if the sodium potassium pumps are able to function at normal speed the reduced number of pumps would increase the time taken for the muscle to return the sodium to the SR and potassium to the sarcoplasm This may increase the time taken for the muscle to be ready to respond to a signal from a nerve which stimulates a contraction Haller et al 1998 also observed that after exercise the concentration of potassium in the blood rose much higher in McArdle people compared to people unaffected by McArdle s He suggested that the body might release more potassium into the blood in an attempt to compensate for the sodium potassium pumps not functioning fast enough Information from studies of people unaffected by McArdle s are that potassium levels in the blood increase in proportion to the amount of exercise being performed Medbo and Sejersted 1990 Regular training appears to increase the total number of sodium potassium pumps in the muscle cells It seems likely that following exercise sodium potassium pumps remove potassium from the blood and from the area between cells and return the potassium to the sarcoplasm It has been found that regular aerobic exercise increases the amount of exercise McArdle people can do see section 4 2 2 If aerobic training leads to an increase in the number of sodium potassium pumps this may contribute to the positive effect of aerobic exercise for McArdle people 4 5 4 Treatment for contractures Contractures occur if a McArdle person continues to exercise or to use a muscle after pain is felt Exercises that can lead to contracture can include moving exercise such as running or static exercise such as squatting A list of some of the types of exercises that can lead to muscle pain and contracture is given in Table 2 1 If possible it is best to avoid producing a contracture It is not known why contractures cause pain A muscle for example a leg muscle is composed of many muscle cells which group together to form muscle fibres If some of the muscle fibres cramp and shorten they may pull against other muscle fibres which are not cramping Mense et al suggested that as the cramping fibres pull away from the non cramping fibres this may stimulate the nerves thereby creating pain signals There is very little published information on how to treat contractures once they have occurred Mense et al 2001 say that contractures are relieved by rest McArdle people have anecdotally reported the following home treatments use of cool ice packs heat packs strong painkillers gentle massage There is no published information on any of these home treatments and some of these treatments like massage could lead to further damage to the muscles Pain can serve as a warning to protect the muscle from further damage and the use of strong painkillers could lead to the muscle being used which could cause further damage IMPORTANT Contractures may be accompanied by rhabdomyolysis muscle breakdown which can lead to increased creatine kinase levels and myoglobinuria Severe muscle damage may lead to kidney failure which can be fatal See section 5 for further information In the event of severe muscle damage medical attention should be sought The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 57

Recommended Recommended reading reading Serious training training for for eendurance ndurance aathletes thletes bby y RRob ob SSleamaker leamaker RRay ay BBrowning rowning 11996 996 Information Information aabout bout Serious different types types oof f eexercise xercise different Biology Biology CConcepts oncepts aand nd AApplications pplications WWithout ithout PPhysiology hysiology BBy y CCecie ecie SStarr tarr CChristine hristine AA E Evers vers LLisa isa SStarr tarr An An eeasier asier eexplanation xplanation oof f the the role role oof f the the ccalcium alcium sodium sodium aand nd ppotassium otassium ppumps umps see see ppage age 885 5 Essential Essential mmedical edical pphysiology hysiology BBy y LLeonard eonard RR J ohnson Johnson John John HH B Byrne yrne A A mmore ore ccomplicated omplicated explanation explanation oof f the the role role oof f the the ccalcium alcium sodium sodium aand nd ppotassium otassium ppumps umps Muscle Muscle ppain ain uunderstanding nderstanding its its nnature ature ddiagnosis iagnosis aand nd treatment treatment BBy y SSiegfried iegfried MMense ense DDavid avid GG Simons Simons I I J on Jon RRussell ussell 22001 001 Page Page 558 8 Kathryn KathrynBirch Birch The TheMcArdle McArdleDisease DiseaseHandbook Handbook Version Version1 1 1 1 1 1

5 Muscle damage causes raised creatine kinase levels and myoglobinuria Most McArdle people experience muscle pain after a few minutes of intense exercise and should stop and rest until the pain is no longer felt If McArdle people continue to exercise after pain is felt muscle damage may occur Rhabdomyolysis occurs when muscle damage causes the breakdown of skeletal muscle cells There are many special proteins and compounds within muscle cells including creatine kinase CK and myoglobin which are released into the bloodstream when muscle damage occurs The amount of CK in the blood can indicate how much muscle damage has occurred In a blood sample higher CK indicates more muscle damage However McArdle people have higher CK levels than unaffected people even if they have not carried out recent strenuous activity so it is important to know what is normal for each McArdle person so that very high levels can be recognised The broken parts of the muscle cells CK myoglobin and other compounds go into the bloodstream The kidneys act like sieves and after muscle damage has occurred the myoglobin is filtered from the blood and leaves the body in the urine Myoglobin causes urine to have a red cola colour For some people the change in urine colour is the first indication that muscle damage has occurred McArdle people who are experienced at dealing with their symptoms will treat mildly coloured urine by drinking plenty of fluids If it is the first time that a McArdle person has coloured urine or it is darker than usual it is important to seek medical attention because they may be at risk of kidney failure If the muscle damage is severe the broken parts of the cells may clog up kidneys and lead to kidney failure Urgent medical attention should be sought if you are unable to urinate as it could indicate kidney failure Kidney failure can be fatal but early treatment usually allows kidney function to be restored The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 59

5 1 Rhabdomyolysis and acute kidney failure Rhabdomyolysis occurs when muscle damage leads to the breakdown of skeletal muscle cells Muscle cells are like a balloon which is filled with water and lots of little components including creatine kinase and myoglobin When muscle damage occurs the components are released The broken parts of the muscle cells and the components go into the bloodstream and then pass through the kidneys The kidneys act like sieves and filter these broken parts from the blood The smaller bits like myoglobin pass out in the urine producing dark red brown coloured urine known as myoglobinuria An alternative name for myoglobinuria is proteinuria If the muscle damage is severe the parts of the cells may clog up the kidneys Kidney failure occurs if the kidneys become clogged and are unable to function The kidneys also play an important role in keeping the correct concentration of several compounds including potassium sodium and calcium called electrolytes in the bloodstream The kidneys ensure that the concentration of potassium and calcium is maintained If kidney failure occurs the kidneys are no longer able to maintain the correct concentrations of electrolytes If a small amount of rhabdomyolysis occurs the person may feel fine but may have raised CK levels Causes of rhabd It is most likely to lead to weakness and pain in the affected muscle s and dark urine If a very large Immobilisation amount of rhabdomyolysis occurs it could lead to extremely high CK levels in the blood electrolyte stroke and then imbalances acute renal failure and the formation of blood clots in blood vessels Huerta Alard n Surgery if a sur 2005 Extreme physic Hypokalemia w 5 2 Causes of rhabdomyolysis are drugs which levels making a 5 2 1 Causes of rhabdomyolysis in people unaffected by McArdle disease Any condition w There are many causes of rhabdomyolysis in people unaffected by McArdle s These are outlined in Electric shock a Table 5 1 It is likely that these may also increase the chance of rhabdomyolysis in McArdle people Hyperthermia in and would be best avoided hyperthermia is is a reaction to 5 2 2 Causes of rhabdomyolysis in McArdle people rhabdomyolysis In McArdle people rhabdomyolysis is most likely to be caused by excessive exertion during exercise stroke wh Heat This can occur if a McArdle person continues to exercise once pain is felt Hypothermia b Freezing of mus Some drugs have the side effect of rhabdomyolysis in people who are unaffected by McArdle s and Recreational dr recently some of these have been found to also increase the risk of rhabdomyolysis in McArdle prolonged use c people For example the cholesterol lowering drugs known as statins have been reported to Prescribed drug increase the likelihood of rhabdomyolysis in McArdle people See section 12 1 for a list of drugs rhabdomyolysis which may cause rhabdomyolysis in McArdle people inflammation o Excessive amou Voduc et al 2004 recommend that McArdle people should be advised to avoid dehydration Eating excessive dehydration is the lack of water and lack of essential salts like potassium and to seek medical Infections inclu attention if they have dark urine skeletal muscle Metabolic disea Table 5 1 Cause Page 60 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

if a person lies motionless for a long period of time this can compress and damage the muscle E g if an elderly perso n remains in one position for a long time or if a person is drunk and lies motionless for a long time rgical procedure is performed in an improper position or a tourniquet is used for a long period of time cal exertion especially in conditions of high temperature and humidity when potassium levels in the blood are lower than they should be increases the risk of rhabdomyolysis during strenuous h increase the rate of urine production and can lead to depletion of electrolytes such as potassium Abuse of diuretics ma athletes more likely to develop rhabdomyolysis during strenuous exercise which produces major electrolyte losses and dehydration such as severe diarrhoea vomiting or bulimia could lead to rh and lightning strikes ncluding malignant hyperthermia see section 12 3 1 for more information on malignant hyperthermia A symptom of m s an extreme rise in body temperature leading to excessive sweating which can reduce potassium levels Neuroleptic m antipsychotic drugs like butyrophenones phenothiazines and thioxanthenes This can lead to hyperthermia muscle rigid s here people have a core body temperature above 40 5 C being very cold or frozen can reduce the blood flow to the muscles reducing the amount of glucose and energy available scle cells can breakdown and damage the cells rugs such as cocaine and LSD D lysergic acid diethylamide Cocaine can cause rhabdomyolysis by having a toxic effect on can limit the amount of blood flow to the muscles and by inducing coma and immobility for a long time gs Statins are some of the most widely prescribed drugs in the United States Statins are well known to have the side eff s Rhabdomyolysis may be triggered by statins within a short period of commencing the drug or many years later Statin of the muscles myositis causing pain and weakness of the muscles unts of alcohol either binge drinking or alcohol abuse can lead to pain and swelling of the muscles e quantities of liquorice often found in sweets which has a component that reduces levels of potassium in the kidney uding influenza Epstein Barr virus herpes simplex virus HIV sepsis legionella infection bacteria pyomyositis bacterial in es ases including McArdle disease Tarui disease phosphoglycerate mutase deficiency and carnitine palmitoyltransferase de es of rhabdomyolysis in people unaffected by McArdle s summarised from Huerta Alard n 2005 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Table 5 1 Causes of rhabdomyolysis in people unaffected by McArdle s summarised from Huerta Alard n 2005 Page 61 Immobilisation if a person lies motionless for a long period of time this can compress and damage the muscle E g if an elderly person has a fall or a stroke and then remains in one position for a long time or if a person is drunk and lies motionless for a long time Surgery if a surgical procedure is performed in an improper position or a tourniquet is used for a long period of time Extreme physical exertion especially in conditions of high temperature and humidity Hypokalemia when potassium levels in the blood are lower than they should be increases the risk of rhabdomyolysis during strenuous exercise Diuretics are drugs which increase the rate of urine production and can lead to depletion of electrolytes such as potassium Abuse of diuretics may lower potassium levels making athletes more likely to develop rhabdomyolysis during strenuous exercise Any condition which produces major electrolyte losses and dehydration such as severe diarrhoea vomiting or bulimia could lead to rhabdomyolysis Electric shock and lightning strikes Hyperthermia including malignant hyperthermia see section 12 3 1 for more information on malignant hyperthermia A symptom of malignant hyperthermia is an extreme rise in body temperature leading to excessive sweating which can reduce potassium levels Neuroleptic malignant syndrome is a reaction to antipsychotic drugs like butyrophenones phenothiazines and thioxanthenes This can lead to hyperthermia muscle rigidity and rhabdomyolysis Heat stroke where people have a core body temperature above 40 5 C Hypothermia being very cold or frozen can reduce the blood flow to the muscles reducing the amount of glucose and energy available for movement Freezing of muscle cells can breakdown and damage the cells Recreational drugs such as cocaine and LSD D lysergic acid diethylamide Cocaine can cause rhabdomyolysis by having a toxic effect on muscle cells prolonged use can limit the amount of blood flow to the muscles and by inducing coma and immobility for a long time Prescribed drugs Statins are some of the most widely prescribed drugs in the United States Statins are well known to have the side effect of rhabdomyolysis Rhabdomyolysis may be triggered by statins within a short period of commencing the drug or many years later Statins can also cause inflammation of the muscles myositis causing pain and weakness of the muscles Excessive amounts of alcohol either binge drinking or alcohol abuse can lead to pain and swelling of the muscles Eating excessive quantities of liquorice often found in sweets which has a component that reduces levels of potassium in the kidney Infections including influenza Epstein Barr virus herpes simplex virus HIV sepsis legionella infection bacteria pyomyositis bacterial infection of the skeletal muscles Metabolic diseases including McArdle disease Tarui disease phosphoglycerate mutase deficiency and carnitine palmitoyltransferase deficiency Causes of rhabdomyolysis in people unaffected by McArdle disease domyolysis in people unaffected by McArdle disease Page 61

5 3 Symptoms of rhabdomyolysis 5 3 1 General symptoms General symptoms are feeling ill fever increased heart rate tachycardia nausea and vomiting The early complications include an increased level of potassium in the blood hyperkalemia very low levels of calcium in the blood hypocalcaemia elevated liver enzymes cardiac dysrhythmias and cardiac arrest while the late complications include acute renal failure and clotting of blood in the blood vessels called disseminated intravascular coagulation 5 3 2 Raised creatine kinase levels in the bloodstream Creatine kinase CK is also known as creatine phosphokinase CPK CK levels in the blood can be used as an indicator of muscle damage because the amount of CK released into the blood is approximately proportional to the amount of muscle damage the more muscle cells that are damaged during exercise the higher the amount of CK will be released from the damaged cells into the blood Normal CK levels in men unaffected by McArdle s are 50 500 U l although those of women are often 25 lower Cush 2005 In people unaffected by McArdle s raised CK level above 5000 U l indicates severe muscle injury and suggests an increased risk of kidney failure Huerta Alard n 2005 An increase in CK due to rhabdomyolysis will occur within 12 hours of the onset of muscle injury The CK level will reach a peak in 1 3 days and begin to decrease 3 5 days afterwards The peak CK level may indicate the likelihood of kidney failure Huerta Alard n 2005 In McArdle people the CK levels can rise to several thousand U L indicating marked rhabdomyolysis after intense exercise Lucia et al 2008a This is known as hyper CK emia CK is determined in a laboratory using a sample of blood further information on CK tests is provided in section 2 3 4 A blood sample will usually be taken from a vein in the arm or hand and it will take a period of time for the CK to be transported from the small blood capillaries in the damaged muscles for example the leg muscles and into the veins in the arms where the blood is taken If frequent blood samples were taken after a McArdle person carried out intense exercise it would be expected that the amount of CK in the blood would gradually increase reach a plateau a maximum and then begin to decrease as the kidneys begin to remove the CK and other proteins from the blood and they will leave the body as waste for example in the urine In people unaffected by McArdle s CK levels also increase but to a lower level if muscle damage occurs during exercise Garrett and Kirkendall 2000 say that that the maximum level of CK usually occurs 2 to 4 days after exercise However different types of exercise produce a maximum CK level at different times after exercise Garrett and Kirkendall 200 say that for people unaffected by McArdle s downhill walking results in a maximal serum CK level at 24 hours whereas biceps curls or leg resistance exercises attained a maximal CK value at 3 or 4 days after exercise Resting CK levels vary depending on gender age ethnicity the size of muscles and general fitness for people unaffected by McArdle s Brancaccio et al 2007 and I imagine that similar variations apply to McArdle people Although many scientific papers quote the CK levels in McArdle people when resting or after intense exercise I was not able to find any papers which tracked the changes in CK level during the hours and days after exercise Anecdotally it has been suggested that for a McArdle person the amount Page 62 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

of CK in the blood reaches the maximum amount approximately 24 hours after muscle damage and then reduces by 30 to 50 in each 24 hours thereafter 5 3 2 1 McArdle people always have raised CK levels even at rest McArdle people always have raised CK levels even at rest All 100 of McArdle people have CK levels above 200 U l at rest Lucia et al 2008a Lucia et al found that approximately half approximately 50 of McArdle people have CK levels above 1000 U l at rest In a study of 45 McArdle people Quinlivan et al 2010 reported that the average CK level was 2 471 IU l Anecdotally the CK levels at rest which are normal for a McArdle person seem to vary from person to person If you have a CK test it is important to inform the family doctor or medical professional that you have McArdle s It is also useful to know your normal CK range 5 3 3 Myoglobinuria blood in the urine It can be useful to quantify the amount of myoglobin in the blood and urine as a measure of the amount of muscle damage which has occurred Although the amount of myoglobin in the blood can be measured CK levels remain higher in the blood for longer than myoglobin levels The half life of CK is 1 5 days Myoglobinuria blood in the urine can cause the urine to be a colour ranging from pink tinged to cola coloured to dark black Huerta Alard n 2005 The red brown colour is usually seen when the myoglobin concentrations in urine are above 300mg l A urine dipstick can be used to test for myoglobinuria The dipsticks are designed to detect haemoglobin at concentrations of 0 3mg l but should also detect similar concentrations of myoglobin Huerta Alard n 2005 IMPORTANT Urgent medical attention should be sought if you are unable to urinate as it could indicate kidney failure Greenberg 2005 5 3 4 Treatment of rhabdomyolysis In order to protect the kidneys the person will need vigorous hydration Huerta Alard n 2005 The main treatment is aggressive fluid replacement with saline water containing salts usually delivered via an intravenous drip The amount of urine which is passed will probably be measured to determine how much fluid is passing through the kidneys A catheter may be inserted into the urethra to achieve this or you may be asked to urinate into a cup bedpan or other measuring device The quicker rehydration is achieved the lower the risk of kidney failure Mannitol and bicarbonate are often given after saline has been given Mannitol may reduce the amount of cell injury may reduce the amount of heme a component of hemoglobin which is left in the tubes of the kidneys heme deposits are bad for the kidneys and also may help to keep the tubes of the kidney open is a renal vasodilator Sometimes other diuretics such as furosemide are given to try to encourage the flow of liquids through the kidneys After rhabdomyolysis a large amount of acidic urine may pass through the kidneys Acidic urine may be damaging to the kidneys Bicarbonate would help to neutralise the acidic urine and could help to reduce the level of damage However there is not very much clinical evidence for use of bicarbonate or mannitol and just the use of saline alone seems to have an equal result Huerta Alard n 2005 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 63

Even if immediate treatment is give some people may have kidney failure acute renal failure The treatment for acute renal failure is an intravenous drip to provide the correct amount of fluid to make sure the acidity is correct and to add any electrolytes such as potassium or calcium which are required Dialysis may be needed to remove urea and potassium which are released during muscle damage It is very important to correct the concentration of potassium in the bloodstream as hyperkalemia can lead to cardiac arrest the heart stopping At the most extreme advanced life support airway breathing and circulation may be required IMPORTANT Kidney failure can be fatal but early treatment usually allows kidney function to be restored The Muscular Dystrophy Campaign recommends that you get prompt medical help if you have any of the symptoms which could indicate kidney failure such as myoglobinuria swollen and tender muscles or flu like symptoms source http www muscular dystrophy org about_muscular_dystrophy conditions 124_mcardles_disease 5 3 5 McArdle people are at an increased risk of rhabdomyolysis raised creatine kinase levels and kidney failure McArdle people are at an increased risk of muscle damage rhabdomyolysis when they exercise McArdle people always have raised creatine kinase levels even at rest which may suggest that even a small amount of movement is producing a small amount of muscle damage McArdle people should stop exercising when they feel muscle pain Continuing to exercise once severe pain is felt could result in muscle damage and potential kidney failure Lucia et al 2008a reported that when McArdle people continued to exercise despite feeling severe pain myoglobinuria occurred in about half 50 of McArdle people with a quarter 25 suffering from renal failure which required hospital treatment Recommended reading Bench to bedside review Rhabdomyolysis an overview for clinicians by Ana L Huerta Alard n Joseph Varon and Paul E Marik Crit Care 2005 9 2 158 169 This paper is the source for most of the information given here about rhabdomyolysis in people unaffected by McArdle s McArdle disease what do neurologists need to know Alejandro Lucia Gisela Nogales Gadea Margarita P rez Miguel A Mart n Antoni L Andreu and Joaqu n Arenas For information about CK levels which are normal for McArdle people and rhabdomyolysis in McArdle people Page 64 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

6 Sources of energy in muscle cells Energy for muscle contractions originally comes from food During digestion in the stomach and intestine food is broken down into smaller units for example carbohydrates are broken down into simpler compounds including glucose Glucose released during digestion is carried by the bloodstream around the body Muscle cells take up glucose from the blood and within the muscle cell most of the glucose is bound together to form a compound called glycogen Glycogen is the main way in which carbohydrates are stored in muscle cells During exercise any free glucose in the muscle cells are quickly used up In people unaffected by McArdle s muscle glycogen phosphorylase begins to unbind the stored glycogen This releases glucose which can be used to provide energy for movement In McArdle people this enzyme does not function so when the muscle cells quickly use up any free glucose within the cell they run out of energy The lack of energy prevents movement and causes pain and muscle damage McArdle people should rest if pain is felt This rest period enables the body to provide energy from other sources fats and proteins from digested food can be broken down to produce energy Muscle cells can also use glucose which is produced by the liver and carried from the liver to muscle in the bloodstream These energy sources do not require muscle glycogen phosphorylase so they can be used to provide energy in the muscle cells of McArdle people Both of these methods are slower to provide energy than muscle glycogen phosphorylase which is why the McArdle person has to rest before continuing to exercise The energy provided by these sources produces the second wind effect which enables McArdle people to continue to exercise Many studies have been carried out to see which diet is best for McArdle people but there is no obvious consensus at the moment It seems likely that protein carbohydrate and fat are all required by McArdle people Some protein is probably required to rebuild muscles which get damaged and also as a source of energy Carbohydrates are the primary source of energy for muscle cells Simple carbohydrates such as sugar can quickly be digested and begin providing energy to muscle cells whereas complex carbohydrates will provide a slower release of energy Fat is a source of energy which is used to generate the second wind but artificially The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 65

increasing the amount of fat in the body does not seem to increase the ability to exercise Having a sugary drink before exercise can provide glucose to the muscle cells through the bloodstream which can make it easier for McArdle people to exercise However McArdle people should be careful about having sugary drinks too often as there is a risk of becoming overweight Page 66 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

6 1 Methods of producing energy in muscle cells of people unaffected by McArdle s Muscle cells need ATP a form of energy to contract and relax as described in section 4 3 Energy originally comes from food Protein carbohydrates and fats are eaten as part of the diet During digestion these are each broken down into smaller units fats are broken down into fatty acids and glycerol proteins are broken down into amino acids and carbohydrates are broken down into sugars 6 1 1 Storage release and breakdown of carbohydrates to produce energy Carbohydrates are often stored as glycogen in the body and about 75 of the total body glycogen is stored in muscle At rest glucose entering the muscle from the blood is converted to glycogen and very little is used to produce ATP The primary source of ATP at rest is fatty acid oxidation described below Fatty acid oxidation is an aerobic process which supplies 85 of energy needs Berg et al 2008 When exercise begins muscle cells need energy to contract and relax During the first few moments of intense exercise free glucose in the muscle is used to provide energy In people unaffected by McArdle s glycogenolysis then takes place Glycogenolysis is the breakdown of stored glycogen into glucose Muscle glycogen phosphorylase is one if the key enzymes involved in this process The glucose produced by glycogenolysis is then used in glycolysis Glycolysis occurs in the cytoplasm sarcoplasm During glycolysis glucose is broken down into pyruvate Glycolysis is able to produce ATP without requiring oxygen it is therefore anaerobic During glycolysis ATP NADH and pyruvate are produced Pyruvate is then moved from the cytoplasm into the mitochondria Pyruvate is then converted into acetyl CoA Acetyl CoA is then broken down further by the citric acid cycle 6 1 2 Storage release and breakdown of fats to produce energy Fats in food are digested in the intestine and transported around the body to the muscles and other locations They are converted to free fatty acids in the muscles or stored in special cells in the body called adipose tissue When energy is needed fatty acids can be released from the adipose tissue A high level of glucagon see section 6 2 3 is one of several triggers for the cells to release fatty acids but insulin can inhibit the release of fatty acids Free fatty acids released from the adipose tissue can be taken by the blood to the muscle cells Fatty acids are broken down in the mitochondria by a process called fatty acid oxidation or beta oxidation Fatty acid oxidation produces NADH FADH2 and Acetyl CoA Acetyl CoA is broken down further in the citric acid cycle to produce more NADH FADH2 and ATP NADH and FADH2 are then broken down further to produce more energy If a very high amount of fatty acid oxidation occurs particularly in the liver very large amounts of Acetyl CoA are produced This is called ketogenesis and can result in the production of ketone bodies If fat is the main only source of energy then muscle will use these ketone bodies to produce energy and will leave any glucose in the blood so that it can be transported to and used by the brain These fats can be broken down further in the citric acid cycle The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 67

6 1 3 Breakdown of proteins to produce energy Proteins are more important for use as building blocks to build strengthen and repair the body rather than a source of energy However some amino acids released from proteins during digestion can be taken in the blood to the muscle cells These amino acids can be broken down in the citric acid cycle 6 1 4 Acetyl CoA from carbohydrates fats and proteins can be broken down in the citric acid cycle The citric acid cycle is also known as the tricarboxylic acid TCA cycle or the Krebs cycle Acetyl CoA is produced from the breakdown of carbohydrates fats and proteins as described above In the citric acid cycle acetyl CoA is broken down to produce NADH FADH2 and carbon dioxide NADH and FADH2 are then used to produce ATP by oxidative phosphorylation 6 1 5 NADH and FADH2 from the breakdown of carbohydrates fats and proteins is used to produce ATP by oxidative phosphorylation NADH is produced by the breakdown of carbohydrates fats and amino acids FADH 2 is also produced from the breakdown of fats and amino acids The breakdown of NADH and FADH2 is a process called oxidative phosphorylation It is called oxidative because it requires oxygen and it therefore aerobic Both NADH and FADH2 are supercharged with hydrogen which can be used to power a process called the electron transport chain which produces lots of ATP 6 2 Glucose from the blood is an important source of energy for muscle cells 6 2 1 Glucose is transported from the blood into muscle cells Muscle cells require energy ATP to contract and relax Glucose is used as a source of energy and is broken down by muscle cells to release ATP GLUT 4 is a special protein called a transporter which takes glucose from the blood into muscle cells At rest insulin can bind to GLUT 4 and stimulate make the GLUT 4 transporter take up glucose from the blood into the muscle cells During exercise GLUT 4 is stimulated in a different way possibly by calcium and Pi the role of calcium and Pi in exercising muscle is discussed further in section 4 3 6 2 2 Excess glucose is stored as glycogen If there is an excess of glucose in the blood more than is needed it can be taken up by the muscle cells and converted to glycogen by a process called glycogen synthesis Glycogen can then be stored in the muscle cells until energy is needed for example during exercise In people unaffected by McArdle s when this energy is needed a group of enzymes including muscle glycogen phosphorylase are used to convert glycogen into glucose and use the glucose to produce energy McArdle people are able to store glucose as glycogen as normal but are not able to convert the glycogen back into glucose This results in increased stores of glycogen in the muscle cells of McArdle people This is why McArdle disease is known as a Glycogen Storage Disease GSD Page 68 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

6 2 3 Insulin and glucagon are two hormones which maintain the right amount of glucose in the bloodstream The human body needs a constant amount of glucose in the bloodstream This is achieved using the hormones insulin and glucagon both of which are produced by the pancreas Insulin and glucagon work in opposite directions to lower and raise the levels of glucose in the blood If blood glucose levels are high this stimulates islet cells within the pancreas to release insulin into the blood Insulin then has an affect on several cells including muscle cells red blood cells and fat cells These cells respond to insulin and absorb glucose out of the blood This lowers the level of glucose in the blood to the normal amount As the amount of glucose in the blood gets lower less insulin is produced Insulin can stimulate GLUT 4 to take glucose from the bloodstream into the muscle cells and stimulate glycogen synthesis Insulin can also stimulate the body to convert excess glucose into fats for storage In the opposite manner if blood glucose gets low for example between meals or during exercise more glucagon is produced by the pancreas this affects many cells especially the liver Excess glucose is stored as glycogen in the liver as well as the muscles and glucagon stimulates liver glycogen phosphorylase to convert glycogen into glucose which is then released into the bloodstream Biesalski 2005 Diabetes is the inability to control the level of glucose in the blood Diabetes and McArdle disease are discussed further in section 13 4 6 3 In people unaffected by McArdle s enzyme activity of muscle glycogen phosphorylase is controlled to maintain the right amount of glucose within the cell In people unaffected by McArdle s the enzyme activity of muscle glycogen phosphorylase is strictly controlled in order to maintain the correct amount of glucose within the cell The function of muscle glycogen phosphorylase is to help to breakdown glycogen into glucose to provide energy for muscle contractions But it is also important that muscle glycogen phosphorylase can be inactivated so that it does not continue this process when the muscles are at rest which would lead to an excess of glucose in the cell Muscle glycogen phosphorylase can be activated and inactivated an infinite number of times A very basic analogy would be to say that the activity can be turned on and off like a light switch There are several layers of control of the activity of muscle glycogen phosphorylase which includes the physical structure of the enzyme and also the presence of ligands and cofactors These are very complicated so only a brief explanation is given below 6 3 1 Muscle glycogen phosphorylase is made of several identical subunits which require the presence of phosphate As described in section 3 1 ribosomes use PYGM mRNA as a template to assemble amino acids into a chain also known as polypeptide chains Initially two of these chains bind together this is called a dimer shown in Figure 6 1 The dimer is often known as phosphorylase b A dimer is not the right shape for enzyme activity Several steps are needed to make the dimer the right shape Several compounds such as ATP bind to the chains of the dimer and another enzyme called The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 69

phosphorylase b kinase adds a phosphate to each chain in the dimer The presence of these phosphates encourages the polypeptide chains of the dimer to change shape and to bind together with another dimer The four polypeptide chains are together known as a tetramer The tetramer is often known as phosphorylase a Barford and Johnson 1992 Johnson 1992 The tetramer is now ready to be activated Protein phosphatase 1 can work in the opposite way to phosphorylase b kinase Protein phosphatase 1 can remove the phosphate This makes the tetramer fall apart back into dimers Insulin can stimulate protein phosphatase 1 to remove the phosphate Johnson 1992 Figure 6 1 3D model of human muscle glycogen phosphorylase a shown as a dimer of a green and a blue polypeptide chain Locations of important sites are shown by colour with the atoms of the side chains shown as spheres AMP is shown in aquamarine the AMP binding site is shown in sky blue serine 15 is shown in magenta nucleoside inhibitor site is shown in purple glucose binding site is shown in orange and PLP binding site is shown in yellow All known mutations are shown in red in the green polypeptide chain with R50X and G205S not visible labelled Picture created using the PyMol program using file 1z8d mmol from EBI website based on PDB ID 1z8d Lukacs et al 2006 6 3 2 Muscle glycogen phosphorylase activity is controlled by ligands and cofactors Muscle glycogen phosphorylase does not always need to be active Activity is most needed during exercise when energy is required The activity of muscle glycogen phosphorylase is under strict control Mutalik and Venkatesh 2005 Special compounds called ligands bind to binding sites spread over the enzyme Ligands are used to control the speed at which muscle glycogen phosphorylase breaks down glycogen Johnson 1992 These sites have names like catalytic side active site and nucleoside AMP inhibitor site When glycogen binds to the active site it can be Page 70 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

broken down into glucose 1 phosphate which is then broken down by other enzymes into glucose Muscle glycogen phosphorylase also has a cofactor which is needed for it to be active The cofactor is called pyridoxal 1 phosphate PLP and is produced from vitamin B6 PLP attaches onto muscle glycogen phosphorylase near to the catalytic site Johnson 1992 Klinov and Kurganov 2001 6 3 3 The levels of glycogen may affect the activity of muscle glycogen phosphorylase During activation of muscle glycogen phosphorylase having some glycogen nearby helps to increase how active muscle glycogen phosphorylase can be However abnormally high levels of glycogen may reduce muscle glycogen phosphorylase activity Schliselfeld et al 2002 compared the amount of glycogen and phosphorylase activity between unaffected mice and mice genetically modified to have increased amounts of glycogen in their muscles They found an inverse relationship between mouse muscle glycogen phosphorylase activity and the muscle glycogen content The unaffected mice had 52 greater muscle glycogen phosphorylase activity If the same applied in humans this could mean that even if a McArdle person had a very low level of muscle glycogen phosphorylase enzyme activity see section 9 1 4 it may be inhibited by high levels of glycogen in the muscle cells 6 4 How is energy produced in the muscles of McArdle people 6 4 1 Glycogen cannot be broken down into glucose to provide energy for exercise In McArdle people at rest carbohydrates are stored as glycogen within the muscle cells At rest energy is provided to the muscle cells primarily by fatty acid oxidation section 6 1 2 During exercise free glucose within the muscle cells is used up within a few minutes Normally stored glycogen would then be broken down into glucose to provide the muscle cells with energy However in McArdle people the lack of functional muscle glycogen phosphorylase means that this cannot take place Muscle cells of McArdle people are not able to break down glycogen into glucose If McArdle people continue to exercise they will feel muscle pain and tiredness as the muscle cells run out of energy This indicates that the McArdle person should stop exercising If they continue to exercise rhabdomyolysis muscle damage and contractures see section 4 3 may occur However after about 10 minutes taking brief rests as required the pain and tiredness will reduce and McArdle people can continue to exercise with minimal pain or no pain for a long time This is the second wind phenomenon The second wind occurs because the muscles begin to get energy from different sources glucose from the liver and free fatty acids from adipose tissue Vissing and Haller 2003 6 4 2 Other mechanisms provide the energy needed for the second wind If McArdle people rest for a few minutes the muscle cells will begin to produce energy by the break down of fatty acids and amino acids Fatty acids will be released from body stores of adipose tissue into the bloodstream and taken to the muscle The fats will be broken down by fatty acid oxidation citric acid cycle and oxidative phosphorylation These processes will generate ATP energy Amino acids can also be broken down by the citric acid cycle and oxidative phosphorylation to produce ATP Since these processes require oxygen McArdle people begin to breathe more heavily which The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 71

increases the amount of oxygen in the bloodstream and this oxygen is then taken to the muscle cells Hilton Jones 2001 In addition glucose is also released from the liver and transported in the bloodstream to the muscle cells This glucose can then be broken down by glycolysis to generate pyruvate and NADH Pyruvate is broken down further in the citric acid cycle to produce NADH and FADH2 NADH and FADH2are both used to generate energy by oxidative phosphorylation Although some McArdle people may not have experienced a second wind McArdle s specialists agree that all McArdle people are capable of it Quinlivan and Vissing 2007 During an ischaemic forearm test see section 2 3 1 1 a cuff is placed around the arm or leg to restrict blood flow Restricted blood flow is called ischaemia This reduces the amount of glucose and free fatty acids able to get into the exercising muscle and prevents the muscle from getting a second wind 6 4 3 The production of energy by other mechanisms is not as efficient in McArdle people Normally the breakdown of glucose which has been produced from glycogen generates pyruvate McArdle people don t produce as much pyruvate and this has a knock on effect which reduces the ability of McArdle people to produce energy by oxidative phosphorylation The result of this decreased rate of oxidative phosphorylation is that the amount of oxygen consumed the amount of oxygen used to produce energy is reduced in McArdle people Haller et al 2006 6 4 4 The way in which the body of a McArdle person responds to exercise During exercise the heart increases the number of contractions per minute This increases the pulse rate and the heart rate Porte et al 1966 were the first to test the effect of exercise on cardiopulmonary system and to find an accelerated heart rate response is usually seen When exercising the heart rate of McArdle people increases much more steeply than people unaffected by McArdle s This may be so that the blood can pump more oxygen from the lungs to the muscle and also so that the blood can carry more glucose from the liver to the muscles During exercise muscles breakdown fuel sources such as carbohydrates and fats and generate waste products such as potassium phosphate lactate and carbon dioxide described further in section 5 As the amount of these waste products increases it stimulates nerves in the exercising muscles These nerves are linked up with nerves which run throughout the body called the sympathetic nervous system Stimulation of nerves in exercising muscles in turn leads to stimulation of the sympathetic nervous system Sympathetic nerves cause the heart to beat faster producing an increase in heart rate In addition muscle pain can also stimulate the sympathetic nervous system Information from Voduc et al 2004 and Khan 2005 McArdle people also breathe more heavily in response to exercise If a person breathes in and out more than is expected this is known as hyperventilation However McArdle people do not use as much oxygen as expected This can be measured as VO2 max Page 72 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

6 4 4 1 VO2 max VO2 peak McArdle disease appears to have an effect upon the rate of breathing by causing hyperventilation breathing faster or deeper than usual and also upon the amount of oxygen which is used by the body Air that is breathed into the lungs contains several kinds of gas including oxygen and carbon dioxide Air that is breathed in has more oxygen and less carbon dioxide In the lungs a lot of the oxygen travels into tiny blood vessels and binds to red blood cells This oxygen is carried around the body to many locations including the muscles The oxygen is then used in chemical reactions with fuel sources such as fat or carbohydrate These chemical reactions produce energy and produce carbon dioxide as a waste product The carbon dioxide is carried by the red blood cells back to the lungs The air that is breathed out has more carbon dioxide and less oxygen It is possible to accurately measure how much carbon dioxide and oxygen is breathed in and out This can be used to calculate how much has been used for the chemical reactions in the muscles In order to determine VO2 max the person being tested wears a type of oxygen mask over their head This allows measurement of the amount of oxygen they breathe in oxygen consumption called VO2 and the amount of carbon dioxide breathed out called VCO2 These two numbers can be combined to produce a VCO2 VO2 ratio When the person exercises at maximum capacity and has the maximum oxygen uptake this is called VO2max When a person is doing aerobic exercise with the maximum possible effort the VO2 max is determine by the capacity of the heart lungs and blood to transport oxygen to the muscles and the use of oxygen by the muscles during exercise Heyward 2006 In exercise tests a McArdle person may be asked to exercise at approximately 40 of VO2max In McArdle people this level of exercise causes a high heart rate and a high level of perceived exhaustion it feels like really hard work to pedal until 8 10 minutes into the exercise when the second wind occurs Abramsky 2001 Some types of exercise cause a peak rather than a maximum rate of oxygen use VO2 peak is the highest rate of oxygen consumption Absolute VO2 is the actual amount of oxygen used for leg or arm cycle ergometer Relative VO2max is used to determine how good the cardio respiratory heart lungs and blood fitness is Heyward 2006 Many studies report that the amount of oxygen used is reduced in McArdle people compared to unaffected people Hagberg et al 1982 showed that McArdle people had hyperventilation in response to exercise but did not not use as much oxygen as expected Oxygen is used to produce energy in muscle cells but if some oxygen is breathed out not as much is being used as expected Some research suggested that the result of this decreased rate of oxidative phosphorylation is that the amount of oxygen consumed VO2max the amount of oxygen used to produce energy is less than half the amount of people unaffected by McArdle s VO2max was on average 14 ml x kg 1 x min 1 in McArdle people compared to 37 7 ml x kg 1 x min 1 in unaffected people Haller et al 1985 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 73

Although it has been reported that the amount of oxygen VO2 used by McArdle people may be less than unaffected people this may have been difficult to measure because there are big differences between the amount of exercise McArdle people can do compared to unaffected people Dochartaigh 2004 Dochartaigh et al suggested that if the amount of exercise was kept similar it would become clear that the VO2would be higher in McArdle people than unaffected people They found that the amount of oxygen used VO2 and amount of carbon dioxide breathed out VCO2 were both higher in McArdle people The authors suggest that McArdle people may use more oxygen because more oxygen is needed to produce energy from the breakdown of fats than the amount of oxygen needed to breakdown carbohydrates Riley et al 1993 had also seen that the amount free fatty acid in the blood was increased during exercise and suggested that the use of fat to produce energy could explain the unusual breathing patterns like hyperventilation seen in McArdle people 6 4 5 How would having a sugary drink before exercise increase the amount of energy available for the muscles of McArdle people A sugary drink sucrose dissolved in water would be quickly digested broken down into glucose and fructose and absorbed into the bloodstream The glucose will be carried to the muscle cells The glucose could then be used by the muscle cells to produce pyruvate by the process of glycolysis and this pyruvate could then be used to produce energy Having a sugary drink a couple of minutes before exercise seems to put the glucose into the bloodstream faster than the liver is able to In the liver glycogen which is stored in the liver must be converted to glucose by liver glycogen phosphorylase before the glucose can be released into the bloodstream 6 4 5 1 A sugary drink may inhibit the second wind There is evidence that having a very high level of glucose in the blood may inhibit the transition to second wind Having a sugary drink or a glucose infusion given intravenously will lead to a very high level of glucose in the blood Vissing et al 1992 tested the effect of a glucose infusion on McArdle people They found that a glucose infusion raised glucose levels hyperglycaemia and raised insulin levels hyperinsulinemia in the bloodstream They also found that the glucose infusion reduced the normal increase in glucose production release of glucose from the liver and reduced the amount of free fatty acids released in the bloodstream The heart rate also did not increase as much as is usually seen in McArdle people during exercise This may suggest that a sugary drink is most useful for very short term exercise but not very useful for prolonged exercise 6 4 6 The amount of some other enzymes may be increased in the muscle cells of people with McArdle s to compensate for the lack of muscle glycogen phosphorylase It has been found that the amount of some proteins is increased in people with McArdle s possibly to compensate and try to make up for the lack of muscle glycogen phosphorylase Robertshaw et al 2008 found that people with McArdle s had more phosphofructokinase PFK enzyme than people unaffected by McArdle s There are many enzymes involved in the many steps glycolysis the breakdown of glucose to release energy as ATP Glycolysis is the process where glucose is broken down to release energy in the form of ATP There are many steps in this process and PFK is one of several enzymes involved in the breakdown of glycogen Page 74 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Robertshaw et al 2008 also found that people with McArdle s had more glucose transporter 4 GLUT 4 protein level than people unaffected by McArdle s GLUT 4 is involved in taking glucose from the blood into the muscle cells GLUT 4 is discussed further in section 6 2 1 The authors suggested these changes may occur in the cells of people with McArdle s to increase the amount of glucose taken from the bloodstream into the muscle cells and that this may explain why oral sucrose can alleviate symptoms during exercise Muscle 2 AMP activated protein kinase 2AMPK is an enzyme which is involved in the production of energy in many different ways When muscle cells exercise and begin to suffer from a lack of energy AMPK becomes more active and helps to increase the amount of energy available for the muscle cell by increasing muscle glucose uptake and stimulating fatty acid oxidation Nielsen et al 2002b found that during exercise an increase in muscle 2AMPK activity was seen in McArdle patients but not in unaffected people This result may suggest that the body of a McArdle person will try to overcome the lack of muscle glycogen phosphorylase by increasing the activity of a different enzyme When there are excess levels of glucose in the body for example when digestion of a meal results in the release of lots of glucose it is converted into glycogen so that it can be stored until needed Glycogen synthase is an enzyme which helps to convert glucose into glycogen By producing glycogen glycogen synthase works in the opposite manner to muscle glycogen phosphorylase During exercise glycogen synthase activity was decreased in McArdle people and increased in unaffected people Glycogen synthase activity appears to be increased by glycogen breakdown and decreased by AMPK activation Nielsen et al 2002b 6 5 Non muscle isoforms of glycogen phosphorylase breakdown glycogen into glucose 1 phosphate in other areas of the body Mammals have three very similar forms of glycogen phosphorylase within their body The DNA sequence and the amino acids which make up these enzymes are very similar and for this reason these enzymes are known as isoforms Each isoform is expressed predominantly in the respective tissue brain muscle or liver Newgard et al 1988 The muscle and brain isoforms have greater similarity to each other than to the liver isoform Hudson et al 1993 The human brain isoform is slightly longer so that it is 862 amino acids long compared to 846 for the human liver isoform and 841 for the human muscle isoform Each gene is located on a different chromosome The PYGB gene for the brain isoform is located on chromosome 20 the PYGL gene for the liver isoform is located on chromosome 14 and the PYGM gene for the muscle isoform is located on chromosome 11 Newgard et al 1988 Glaser et al 1989 There are control regions located next to each gene to control the location within the body where each isoform is produced All three isoforms brain muscle and liver glycogen phosphorylase break down glycogen into glucose 1 phosphate 6 5 1 Muscle glycogen phosphorylase Muscle glycogen phosphorylase is the only form of glycogen phosphorylase produced by skeletal muscles except see 6 5 4 In people unaffected by McArdle s muscle glycogen phosphorylase is able to breakdown glycogen to glucose 1 phosphate to provide a source of energy for muscle contractions In the skeletal muscle of McArdle people there is no or very little muscle glycogen phosphorylase leading to McArdle disease Brain glycogen phosphorylase and liver glycogen The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 75

phosphorylase have not been found in adult skeletal muscle as shown by the lack of a positive phosphorylase stain in a muscle biopsy from a McArdle person section 2 3 2 Adult skeletal muscle contains the genes for brain and liver glycogen phosphorylase but they are turned off so that they are not used to produce enzyme It has been suggested that a potential therapy for McArdle disease could be to use drugs to turn on these genes leading to the production of brain or liver glycogen phosphorylase in skeletal muscle see section 16 3 1 6 5 2 Brain glycogen phosphorylase Brain glycogen phosphorylase is a form of glycogen phosphorylase which is found in smooth muscle such as the stomach wall wall of the intestine wall of the bladder probably the wall of the womb Brain glycogen phosphorylase is also found in the brain and in the heart 6 5 2 1 The brain isoform is also known as the foetal isoform Historically it was believed that the brain isoform was the only isoform of glycogen phosphorylase expressed in a foetus a foetus is the name for a baby in the womb prior to birth However some researchers disagree Newgard et al 1991 found that the Pygm mRNA was the predominant mRNA of rabbit foetal muscle and that Pygb mRNA was barely detectable Thus our studies of phosphorylase mRNA in the rabbit provide no evidence for general predominance of the brain isoform in foetal tissues or for isoform switching from the brain to the liver or muscle forms during development as has been suggested by others Newgard et al 1991 Walker 2006 found there to be a gradual decrease of the brain isoform and a concurrent gradual increase of muscle isoform over time in the sheep foetal muscle and sheep neonatal newly born skeletal muscle By 15 days after birth there was only a trace of the brain isoform in the sheep muscle 6 5 2 2 Mutations in brain glycogen phosphorylase have not been reported No humans have been reported who have mutations in PYGB gene which encodes brain glycogen phosphorylase If the brain isoform is also the predominant foetal isoform mutations in the PYGB gene may be lethal and prevent development and survival of the foetus 6 5 3 Liver glycogen phosphorylase Liver glycogen phosphorylase is a form of glycogen phosphorylase which is found in smooth muscle and in many locations where brain glycogen phosphorylase is also found Liver glycogen phosphorylase has been found in the liver intestine and bladder 6 5 3 1 Mutations in liver glycogen phosphorylase cause Hers Disease Hers Disease Glycogen Storage Disease VI is caused by mutations in the PYGL gene Burwinkel et al 1998 6 5 4 After muscle damage regenerating immature muscle produces brain and or liver isoform Mature skeletal muscle cells produce only muscle glycogen phosphorylase However after muscle damage has occurred muscle cells divide to produce new cells to replace the damaged cells These newly dividing cells are called regenerating or immature Immature muscle cells produce other forms of glycogen phosphorylase which are not the muscle isoform At present it is not clear if this is just the brain isoform just the liver isoform or both Page 76 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

6 5 5 A brief discussion about the three isoforms of glycogen phosphorylase It hasn t been possible to definitively state which isoforms of glycogen phosphorylase are found in which tissues In some cases the available literature is contradictory This may be because different detection methods have different levels of sensitivity so some may detect a form of the enzyme which others do not for example methods which detect mRNA may be able to detect much smaller amounts of mRNA than methods which detect protein It should also be noted that much of this information is not based upon humans and is instead based on studies of other mammals such as rat rabbit and sheep To summarise published information it seems that two general statements could be made about the isoforms of glycogen phosphorylase Brain and liver glycogen phosphorylase are often found in the same locations smooth muscle such as bladder and intestine Brain and liver glycogen phosphorylase are not found in the same location as muscle glycogen phosphorylase Muscle glycogen phosphorylase is not detected in bladder or intestine Brain and liver glycogen phosphorylase are not found in skeletal muscle 6 5 6 Non muscle isoforms of glycogen phosphorylase spare the smooth tissue and organs of the body from symptoms of McArdle disease Only limited studies have been performed upon McArdle people to find out which isoforms of glycogen phosphorylase are expressed in which tissues My opinions of the expression of different isoforms in the body of a McArdle person are given in Table 6 1 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 77

Page 78 em uterus testis Kathryn Birch Glycogen phosphorylase in the brain of a person unaffected by McArdle disease is approximately 50 glycogen phosphorylase and 50 muscle glycogen phosphorylase In a McArdle person only brain gly phosphorylase is present This does not appear to have a major effect upon the functioning of the br been suggested that it may have a small effect upon the functioning of the brain but further studies a to prove this see section 10 2 I believe that skin cells express either brain or liver glycogen phosphorylase or both They are unaff absence of muscle glycogen phosphorylase in McArdle disease Glycogen phosphorylase in the heart of a person unaffected by McArdle disease is approximately 50 glycogen phosphorylase and 50 muscle glycogen phosphorylase In a McArdle person only brain gly phosphorylase is present This does not appear to have any effect upon the functioning of the heart 13 5 These are composed of smooth muscle and express both brain and liver glycogen phosphorylase Th unaffected by the absence of muscle glycogen phosphorylase in McArdle disease These are composed of smooth muscle and express both brain and liver glycogen phosphorylase They are unaffected by the absence of muscle glycogen phosphorylase in McArdle disease Glycogen phosphorylase in the heart of a person unaffected by McArdle disease is approximately 50 brain glycogen phosphorylase and 50 muscle glycogen phosphorylase In a McArdle person only brain glycogen phosphorylase is present This does not appear to have any effect upon the functioning of the heart see section 13 5 I believe that skin cells express either brain or liver glycogen phosphorylase or both They are unaffected by the absence of muscle glycogen phosphorylase in McArdle disease Glycogen phosphorylase in the brain of a person unaffected by McArdle disease is approximately 50 brain glycogen phosphorylase and 50 muscle glycogen phosphorylase In a McArdle person only brain glycogen phosphorylase is present This does not appear to have a major effect upon the functioning of the brain It has been suggested that it may have a small effect upon the functioning of the brain but further studies are needed to prove this see section 10 2 Comments in relation to McArdle disease These are composed of smooth muscle and express either brain or liver glycogen phosphorylase or b glycogen phosphorylase has been found in the testis They are unaffected by the absence of muscle phosphorylase in McArdle disease The McArdle Disease Handbook Version 1 1 1 Page 78 Reproductive system uterus testis probably ovaries Kathryn Birch The McArdle Disease Handbook Version 1 1 1 These are composed of smooth muscle and express either brain or liver glycogen phosphorylase or both Brain glycogen phosphorylase has been found in the testis They are unaffected by the absence of muscle glycogen phosphorylase in McArdle disease Digestive system Intestine These are composed of smooth muscle and express either brain or liver glycogen phosphorylase or both digestive tract bladder liver kidney Muscle glycogen phosphorylase has been found in the kidneys of rats unaffected by McArdle disease These organs do not seem to be affected by the absence of muscle glycogen phosphorylase in McArdle disease Lungs Heart Skin Brain Comments in relation to McArdle disease ntestine These are composed of smooth muscle and express either brain or liver glycogen phosphorylase or b dder liver kidney Muscle glycogen phosphorylase has been found in the kidneys of rats unaffected by McArdle disease organs do not seem to be affected by the absence of muscle glycogen phosphorylase in McArdle dise Part of the body of a McArdle person f a McArdle

These express either brain or muscle glycogen phosphorylase or both There is no information about whether the lack of muscle glycogen phosphorylase has any effect upon the nervous system of McArdle people Nervous system spinal chord and nerves Page 79 These are composed of skeletal muscle In a person unaffected by McArdle disease they would express muscle glycogen phosphorylase In a McArdle person no glycogen phosphorylase is present leading to symptoms of McArdle disease Skeletal muscles of the entire body biceps triceps quadriceps calves and many others Kathryn Birch Comments in relation to McArdle disease These are composed of skeletal muscle In a person unaffected by McArdle disease they would glycogen phosphorylase In a McArdle person no glycogen phosphorylase is present leading to McArdle disease These express either brain or muscle glycogen phosphorylase or both There is no information the lack of muscle glycogen phosphorylase has any effect upon the nervous system of McArdle The McArdle Disease Handbook Version 1 1 1 brain cles of the entire body ycogen s quadriceps calves rain It has hers are needed em spinal chord and fected by the Table 6 1 The expression of different isoforms of glycogen phosphorylase in the body of a McArdle person and the effect upon symptoms of McArdle disease Based upon limited published information summarised from information reviewed by Wright 2009 and my opinion Comments in relation to McArdle disease Part of the body of a McArdle person ody of a McArdle xpression of different isoforms of glycogen phosphorylase in the body of a McArdle person and the effect upon symptoms of Mc ited published information summarised from information reviewed by Wright 2009 and my opinion brain ycogen see section hey are both e These ease both Brain glycogen The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 79

6 6 The balance of protein carbohydrate and fat in the diet In the search for an effective treatment for McArdle s many researchers have looked at diet Changing the balance between the amount of protein carbohydrate and fat in the diet is a cheap and easy approach to try to improve the amount of energy available to the muscles There is not a consensus between McArdle s specialists over what the balance of protein carbohydrate and fat in the diet should be and several different theories have been suggested Reasons why each diet has been recommended for McArdle people are given below Some clinical trials to try to prove these theories have been carried out and there are likely to be further trials in the future There is already much information available about balanced diet and healthy eating for the general population such as the information on the NHS website The purpose of this chapter is to consider whether diet may play a role in improving the supply of energy to the muscles and reducing McArdle s symptoms 6 6 1 The role of protein carbohydrate and fat in McArdle s Protein is used as the main component to build and maintain cells in the body It has been suggested that McArdle people may need an increased amount of protein to repair muscle cells due to repeated muscle injury Quinlivan et al 2008 The body can also breakdown protein into amino acids which can be used as a source of energy see section 6 1 3 but this is a slow release form Carbohydrate is principally used to provide energy Simple carbohydrates such as sugar glucose fructose are quickly digested and provide a rapidly available source of energy Complex carbohydrates such as bread or pasta can take longer to digest and provide a slow release of energy Fat is a source of energy Free fatty acids are a source of energy during the second wind Theoretically a high fat diet may increase the amount of free fatty acids available 6 6 2 Research into whether the balance of protein carbohydrate and fat in the diet affects McArdle people Slonim and Groans 1985 had a theory that a diet rich in protein and adequate in carbohydrate would meet the protein requirements caused by the ongoing muscle injury and increased muscle regeneration that are typical of this condition Slonim and Groans 1985 studied one McArdle man who was fed either glucose protein broiled beef or had an intravenous injection of fructose The man was exercised into the second wind and then tested to see how long he could exercise before becoming exhausted He was able to exercise for longer after the protein meal than after having glucose or fructose Kushner 1990 and Maclean 1998 each tried giving McArdle people protein branched chain amino acids supplements but it was not shown to have any benefit see section 7 1 1 2 Jensen et al 1990 compared one McArdle man who was fed either a diet of 15 protein 42 fat and 43 carbohydrate or a high protein diet of 28 protein 29 fat and 43 carbohydrate He was able to exercise for longer following the high protein diet They also tested the man following an intravenous infusion of amino acids proteins They found that giving protein intravenously did not improve the ability to exercise Page 80 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

There are several criticisms of the studies by Slonim et al 1985 and Jensen et al 1990 The first criticism is that they were single case studies they only looked at one person The second criticism is that they were not blinded the people could see what food they were eating and did not have a placebo Much larger studies with many more McArdle people would be needed to produce scientifically valid results see section 17 6 for more details about how the best clinical trials are carried out As mentioned by Quinlivan et al 2008 a further criticism of the high protein diet is that there are no published randomised controlled trials Andersen and Vissing 2008 carried out a crossover open study of seven McArdle people They had either a carbohydrate or protein rich diet for 3 days Their ability to exercise and the amount of exercise they were able to do was compared before and after this diet Each person was tested after each diet The results were that on the carbohydrate diet the participant s heart rate was lower and the participants felt it was easier to exercise than on the protein rich diet Participants had a 25 improvement in maximal oxidative work capacity on the carbohydrate versus the protein diet The authors concluded that the carbohydrate diet not only improves tolerance to everyday activities but will probably also help to prevent exercise induced episodes of muscle injury in McArdle disease Vorgerd and Zange 2007 tested a ketogenic diet This was diet with a high level of fat and a restricted level of carbohydrate in this case 80 fat 14 protein and I calculate there would be approximately 6 carbohydrate Vorgerd and Zange 2007 tested a single McArdle person a 55 year old man with this ketogenic diet for one year The participant had improved muscle symptoms and his ability to exercise was increased between three and ten times what it had been before the trial However no visible changes in muscle energy metabolism were seen within the muscle cells using 31P MRS see section 2 3 6 for explanation of 31P MRS Orngreen et al 2009 investigated whether the bodies of McArdle people compensate for not being able to break down glycogen by instead using more fat to provide energy They studied whether fat was used to provide the muscles with energy in 11 McArdle people Orngreen et al 2009 found that total fat and free fat acids were used more to provide energy during exercise and carbohydrates were used less to provide energy in McArdle people They found that during the start of the second wind fat was used more to provide energy but if more free fatty acids were given it did not increase the ability to exercise even further They conclude that their results suggest that the bodies of McArdle people do use fat to provide energy during prolonged low intensity exercise and this may partially compensate for not being able to produce glucose from glycogen in the muscle cells They also suggest that energy produced using fat could be important in producing the energy for the second wind However they think that there may ultimately be a limit so that increasing the amount of fat does not keep leading to increases in energy Andersen et al 2009 also investigated the role of fat in providing energy during exercise for McArdle people They studied ten McArdle people They compared the amount of exercise the participants were able to do when given either nicotinic acid which prevents the breakdown of fat to produce energy or gave a 20 Intralipid infusion free fatty acids They compared these to a placebo isotonic sodium chloride solution basically a salt solution at the same concentration as found in the body and also glucose Each of these treatments was given as an intravenous injection They compared the effect on the heart rate during exercise As predicted they confirmed that The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 81

giving an Intralipid injection increased the amount of free fatty acid in the blood and that nicotinic acid reduced the levels of free fatty acids by about half Heart rate was significantly higher during exercise in the Intralipid infusion and nicotinic acid trials compared with the placebo and glucose infusion trials an effect that was observed before and after the people had experienced the second wind phenomenon They concluded that although free fatty acids are an important source of energy for muscles of McArdle people during exercise artificially increasing the levels of free fatty acids above those normally present does not lead to an increased ability to exercise They suggest that the lack of breakdown of glycogen into glucose caused by the lack of muscle glycogen phosphorylase in McArdle people may have knock on effects which reduce how much energy can be made from the free fatty acids Fat is made into energy by a series of reactions called the tricarboxylic acid cycle and Andersen et al suggest that methods to improve these reactions will be necessary if researchers want to develop a therapy whereby McArdle people could use more fat to produce energy 6 6 3 Comments on these trials The research published to date described above suggests that protein carbohydrate and fat are all required by McArdle people It is likely that some protein is required to rebuild muscles which get damaged and also as a source of energy but studies by Andersen and Vissing 2008 suggest that a high carbohydrate diet enables McArdle people to exercise more easily than a high protein diet Although free fatty acids are required to produce energy by oxidative phosphorylation in order to generate a second wind research by Orngreen et al 2009 and Andersen et al 2009 suggests that having a very high level of free fatty acids in the blood does not enable oxidative phosphorylation to produce any more energy than usual This data could suggest that a high fat diet would not be of benefit to McArdle people and that a balanced diet with a normal level of fat would be sufficient One criticism of all the trials of different diets is that the participants were not blinded they knew which diets they were being given and would have been able to work out whether they had received the high fat high carbohydrate or high protein diets The participants may have had preconceptions that one diet would help them exercise better and this may have had an effect subconsciously However this effect becomes reduced as the number of participants increases as they are unlikely to all have the same preconceptions IMPORTANT It is important to obtain medical advice before commencing an unusual diet such as those described above This is because without appropriate advice you may not get all the essential nutrients that are required which could lead to a deficiency that could have negative effects on the body Vogerd and Zange 2007 say for a diet such as the ketogenic diet very careful calculation of nutrient composition has to be combined with very restrictive and demanding medical and nutritional supervision 6 6 3 1 The importance of not over eating Protein fat and carbohydrates each contain calories Calories are a measure of energy which is needed for many body processes including providing energy for exercise Calories are burnt by exercise but also in everyday activities An excessive amount is consumed if more calories are eaten than calories used by the body and this can lead to weight gain It is important for McArdle people to try to avoid becoming overweight see section 4 2 3 Page 82 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Recommended reading Most of the information about the production of energy in muscle cells in people unaffected by McArdle s is based upon Molecular Biology of the Cell by Alberts et al 2007 This is a university undergraduate degree level textbook and therefore quite complicated The textbook can be read online for free http www ncbi nlm nih gov bookshelf br fcgi book mboc4 A good source of reliable information on healthy eating and a balanced diet not specific to McArdle people is the NHS website http www nhs uk Livewell Goodfood Pages Goodfoodhome aspx The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 83

Page 84 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

7 Dietary supplements which have been considered for McArdle s McArdle people specialists and scientists have all suggested that taking supplements could theoretically improve McArdle s symptoms by providing an alternative source of energy for the muscle cells or by helping the body to work more efficiently Supplements are foods vitamins or minerals which are eaten drunk or injected in addition to your usual diet Some scientific trials have been performed to see whether taking certain supplements enable McArdle people to exercise more easily However there are criticisms of many of these studies which are explained in more detail in this chapter Medical advice should be obtained before commencing use of a supplement There are a couple of supplements which studies suggest do improve the ability of McArdle people to exercise but they can also have some disadvantages A sugary drink before exercise improves the ability of McArdle people to exercise But it may temporarily prevent a second wind may cause weight gain and is not suitable for unplanned exercise or for McArdle people with diabetes Studies suggest that taking a low amount of creatine as a supplement may help to provide energy to muscle cells and the enable McArdle people to exercise more easily However taking a high amount of creatine as a supplement can cause McArdle people to feel an increased amount of muscle pain when exercising Studies suggest that supplements which do not improve the ability of McArdle people to exercise include amino acids branched chain amino acids vitamin B6 dantrolene sodium and ribose A study on whether verapamil helped McArdle people to exercise was inconclusive Anecdotally some McArdle people have considered taking other supplements including other vitamins and other amino acids However these supplements have not been tested in clinical trials and there is no clinical evidence that they could treat McArdle s The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 85

Descriptions of supplements which it has been suggested may help McArdle s are given below Please note that the inclusion of a supplement in this list DOES NOT indicate that it is a recommended treatment for McArdle s In order to provide the reader with a comprehensive overview the following chapter includes information on supplements which have been shown to be effective to have no effect or a negative effect and for which there is limited information A brief description of the medical scientific reason for these supplements is given And the results of any trials are also given 7 1 Supplements which have been tested as possible treatments for McArdle s 7 1 1 Amino acids 7 1 1 1 Amino acids given intravenously What it is Amino acids are the simple building blocks of proteins Form of the supplement Intravenous injected in solution into a vein Reason why it might help McArdle s Amino acids are used to build proteins for body growth and maintenance Amino acids can also be used as a fuel to provide energy for movement Exercise can lead to rhabdomyolysis muscle damage in McArdle people McArdle people may have a high requirement for amino acids which are used to build and repair muscle damage Results of clinical trials Jensen et al 1990 tested a McArdle man following an intravenous infusion of amino acids proteins They found that giving protein intravenously did not improve the ability to exercise Criticisms of these studies are discussed in section 6 6 2 7 1 1 2 Branched chain amino acids BCAAs What it is BCAAs are made up of branched chains of amino acids a form of proteins which are medium complex Reason why it might help McArdle s proteins are broken down by the citric acid cycle and used to produce energy by oxidative phosphorylation see section 6 1 BCAAs may provide an alternative energy source for exercising muscle Kushner and Berman 1990 and therefore help McArdle people exercise more easily How is it taken orally as a supplement to the usual diet What were the results of clinical trials Kushner 1990 studied three McArdle people before treatment They gave them a short term treatment they tested whether 300mg of BCAAs per kg of body weight consumed 45 60 minutes before exercise had any effect They also gave them longer term treatment one and two months of having 300mg of BCAAs per kg of body weight daily They measured muscle strength and how quickly muscles became tired Neither the short term nor long term treatment had any positive effect Maclean 1998 also tested BCAAs and found that the ability to exercise was worse when taking the supplement Page 86 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

7 1 2 Vitamin B6 What it is B6 is a vitamin Form of the supplement A powdered sachet made up in water as a drink used by Beynon et al as described in the report by Quinlivan et al 2008 B6 is also available as a tablet Reason why it might help McArdle s B6 is used to produce PLP PLP is usually bound to muscle glycogen phosphorylase However not all B6 is bound to muscle glycogen phosphorylase Benyon et al 1996 suggested that in people unaffected by McArdle s the PLP bound to muscle glycogen phosphorylase could serve as a way of buffering the body if the amount of vitamin B6 obtained from the diet varies from day to day For McArdle people the lack of muscle glycogen phosphorylase may reduce the amount of PLP available Their theory was therefore that unless enough B6 is obtained from the diet McArdle people may suffer from a B6 deficiency Results of clinical trials Pheonix 1998 studied a McArdle person who had been taking 50mg of vitamin B6 daily for two years The ability of the participant was compared when he was given either vitamin B6 or a placebo He did not know which he was receiving He felt less well when given placebo but it did not seem to affect the strength of the muscles Quinlivan et al 2008 described an unpublished trial of vitamin B6 by Beynon et al Muscle strength was measured and the amount of B6 in the body was also measured No significant difference was seen with the B6 treatment compared to placebo treatment It should be noted that the data from Beynon et al is unpublished and therefore has not been subjected to peer review or approved for publication by other professionals in the field Izumi et al 2010 described a McArdle woman who was treated with a vitamin B6 supplement 90mg per day for two months Compared with before her CK level decreased an ischaemic forearm test produced a rise in lactate level and she felt that her muscles became tired less quickly after treatment However I suspect that this woman did not have typical McArdle disease The authors report that she had a low level of enzyme activity but they did not perform genetic testing I wonder if this woman had an unusual mutation which resulted in a small amount of functional muscle glycogen phosphorylase Studies suggest that even a small amount of functional enzyme can make a large difference to the severity of McArdle symptoms see 9 1 3 Further studies on McArdle people with typical symptoms of McArdle disease such as a complete absence of functional muscle glycogen phosphorylase would be required to determine the effect of vitamin B6 supplements 7 1 3 Creatine What it is Creatine is a compound which is found naturally in muscle cells It can be made by the body from the amino acids L arginine glycine and L methionine Form of the supplement capsule tablet Reason why it might help McArdle s Muscle cells contain both creatine and phosphocreatine and the balance of each is used to control the levels of ADP and ATP within the muscle cells This helps to maintain a supply of ATP for energy and also to control the level of ADP which can have an effect upon the speed of some energy producing reactions in the body Creatine supplements had The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 87

previously been found to improve the ability to do intense exercise in people unaffected with McArdle s and also people with mitochondrial myopathies see section 2 5 2 What were the results of clinical trials Vogerd 2000 carried out a double blind crossover trial where McArdle people were given either a low dose creatine 150mg of creatine per kg of body weight for one week followed by 60mg of creatine per kg of body weight for four weeks or a placebo They showed that McArdle people were able to exercise more easily after taking the creatine Vogerd et al 2002 then went on to compare high dose 150mg of creatine per kg of body weight to low dose 60mg creatine per kg of body weight When taking high dose creatine the McArdle people reported that they felt muscle pain more frequently during exercise and the level of pain was higher Low dose creatine appeared to help McArdle people to exercise more easily Vogerd 2002 felt that An effective creatine dosage without adverse effects may be between 60 and 150 mg kg daily but that further trials were necessary It was not possible to determine how creatine improved the ability to exercise as treatment did not increase creatine levels in the muscles It was therefore possible that creatine was having a different albeit positive effect upon the body Vorgerd and Zange 2007 7 1 4 Cornstarch such a the commercially available Glycosade What is cornstarch Cornstarch is a source of carbohydrate Form of the supplement powder made into a drink for oral use Reason why it might help McArdle s Cornstarch is not likely to help McArdle s It is used to treat several other Glycogen Storage Diseases GSDs Cornstarch is useful for other GSDs where the main problem is either storing glycogen in the liver or releasing this glycogen from the liver into the blood this is important as it helps the body keep the right amount of sugar in the blood between meals In McArdle people the liver form of the glycogen phosphorylase enzyme works perfectly well so the body is able to store excess sugar as glycogen in the liver and then convert it back into glucose which can be released into the blood when needed Although there have been one or two suggestions published by family doctors that cornstarch might help McArdle s in a similar way to a sugary drink the view of the experts seems to be that cornstarch is NOT likely to help A sugary drink can help as the sugar is very rapidly absorbed through the stomach intestine into the blood and can quickly get to the muscle cells where it is needed quickly in this case would be sometime between 5 mins and 2 hours In contrast cornstarch takes much longer to absorb and for the body to break it down into sugar Sweetman 2009 McArdle people don t need cornstarch to provide energy as they would get this from the food they usually eat If you tried drinking eating cornstarch just before exercise the sugar from the cornstarch would not be released until a long time after you had finished exercise and would not provide any sugar for the muscles during exercise Having cornstarch might be more like eating extra food in addition to your normal meals and might be more likely to result in becoming overweight which is not recommended for McArdle s Page 88 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

What were the results of clinical trials There has been one published study of cornstarch plus vitamin B6 by Sugie et al 2003 however I wasn t able to read it as it was in Japanese The abstract said that it was an open trial which means that the participants knew if they were having the treatment or not which is much less scientifically medically useful In addition the abstract suggests that the McArdle people were given both cornstarch plus B6 which isn t very useful because it wouldn t have been possible to tell which if either was producing a positive result It may be that no other trials of cornstarch have been performed because most researchers have decided based on the science that it would be unlikely to help and therefore not bothered testing it 7 1 5 Dantrolene sodium What it is Dantrolene sodium is a chemical compound Form of the supplement It can be given orally as in the trial by Poels et al 1990 or into the vein by intravenous injection A total of 150mg given as three doses of 50mg was given to participants in the trial by Poels et al 1990 Note An intravenous injection of dantrolene sodium can be used as a treatment for malignant hyperthermia Sweetman 2009 see section 12 3 1 Reason why it might help McArdle s Dantrolene sodium is a muscle relaxant which works directly on the skeletal muscles Sweetman 2009 It was thought that dantrolene sodium might induce or improve the second wind Poels et al 1990 There was also a case report that dantrolene sodium prevented rhabdomyolysis caused by exercise in a person who had rhabdomyolysis and whose muscles quickly became tired during exercise Haverkort Poels et al 1987 However this person had NOT been diagnosed with McArdle s The researchers may have hoped that dantrolene sodium would have a similar positive effect on McArdle people Results of clinical trials Poels et al 1990 carried out a double blind placebo controlled study High doses led to the side effects of tiredness dizziness and muscle weakness Surface EMG results showed that after treatment the muscles of McArdle people responded differently as they became tired during exercise However the overall conclusion was that None of the patients experienced beneficial effect of dantrolene sodium medication Poels et al 1990 7 1 6 Sugar 7 1 6 1 Ribose What it is Ribose is a simple sugar Ribose comes in two forms one of which is D ribose Form of the supplement D ribose dissolved in water as a drink Reason why it might help McArdle s Ribose has several functions in the body It is part of riboflavin which is a building block of two components involved in aerobic energy metabolism Ribose is also used to make ATP the energy source for muscle contraction Ribose is usually obtained from the diet or by making it from glucose Kreider 2009 It has been suggested that giving ribose supplements to people unaffected by McArdle s particularly athletes may help to increase the amount of ATP available in muscle cells Initial studies suggested The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 89

that ribose supplements did appear to help people with either myoadenylate deaminase deficiency see section 2 3 1 or coronary artery disease Kreider 2009 Steele et al 1996 thought that D ribose could be used by the body to produce ATP in McArdle people Results of clinical trials Several studies have been carried out in people unaffected by McArdle s to see if ribose supplements help them exercise for longer but in general they did not have much effect Steele et al 1996 gave McArdle people D ribose There was no significant difference in ability to exercise before or after treatment Participants didn t like taking the ribose Steele et al 1996 said that it did not appear to benefit McArdle people 7 1 6 2 Sucrose glucose What is sucrose Sucrose is a form of sugar Reason why it might help McArdle s Sucrose is rapidly split into glucose and fructose within the muscle cells This process does not require muscle glycogen phosphorylase Glucose and fructose can be used in glycolysis to provide energy Fernandes 2006 This reduces the need to breakdown glycogen into glucose which requires muscle glycogen phosphorylase and does not occur in McArdle people Fernandes 2009 Having a sugary drink just before exercise can increase the level of glucose in the blood Glucose in the blood can be transported and taken into the muscle cells and used to produce energy for exercise This source of glucose should prevent muscle cells running out of glucose and reduce symptoms of McArdle s which are normally induced by exercise such as muscle pain and cramps Form of the supplement used in the trials sucrose powder dissolved in water to produce a drink What were the results of clinical trials Vissing and Haller 2003 gave McArdle people 660ml of a drink containing either 75g of sucrose or artificial sweeteners as a placebo Drinking sucrose increased the level of glucose in the blood and made exercise easier for the McArdle people The McArdle people who were given glucose had a lower heart rate and felt that exercise was easier compared to when they had the placebo Exercise was done 30 40 minutes after drinking the sucrose The exercise was a stationary bicycle ergometer which was cycled for 15 minutes Andersen Haller and Vissing then followed this up in 2008 with the following experiment McArdle people were given either 75 g of sucrose or a placebo 40 minutes before exercise or 37 g of sucrose or a placebo 5 minutes before exercise People were tested with each on different days but did not know which treatment they had each day The results were that having either 75g or 37g of sucrose made exercise easier for McArdle people However taking of sucrose five minutes before exercise had a longer lasting positive effect than taking sucrose 40 minutes before exercise The author s conclusions were This study shows that 37 g of sucrose ingested shortly before exercise has a marked and prolonged effect on exercise tolerance in patients with McArdle disease This treatment is more convenient for the patients and saves more calories than the currently recommended sucrose treatment 7 1 6 3 The pros and cons of drinking a sugary drink before exercise Pros 37g of sucrose in a sugary drink taken 5 minutes prior to exercise has been shown to make exercise easier for McArdle people Andersen et al 2008 It is a quick easy and cheap treatment Page 90 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Cons Having a sugary drink before exercise is a short term treatment and can lead to weight gain Amato 2003 Quinlivan et al 2008 Weight gain and McArdle s is discussed further in sections 4 2 3 and 6 6 3 1 It is not helpful if the exercise is unplanned Quinlivan et al 2008 for example you suddenly have to run for a bus Sugar isn t a suitable treatment for McArdle people who have diabetes Quinlivan et al 2008 It has been suggested that sucrose may prevent or slow down the second wind High levels of sucrose may prevent utilisation of fatty acids as a fuel for prolonged exercise Amato 2003 See 6 4 for a further description of how energy is produce in second wind 7 1 7 Verapamil What it is Verapamil is a chemical compound Form of the supplement It can be given orally as a tablet or by intravenous injection Reason why it might help McArdle s Verapamil is a calcium channel blocker It slows heart rate and is used to treat angina I think that treatment with verapamil was proposed as a way to reduce the increased heart rate which is usually seen in McArdle people when they exercise I am not sure if the authors knew why it might work since they say mechanism of action of the drug in such cases is unclear Results of clinical trials Participants were asked to exercise at home and to keep a diary of the amount of pain experienced to test the effect of the treatment on exercise But none of people tested recorded enough information in their diaries None of the patients with McArdle disease responded to verapamil Lane et al 1984 7 2 Supplements which have not been tested to see if they are effective in McArdle s There are several supplements which McArdle people have mentioned in online chat groups These supplements have not been tested in clinical trials and there is no clinical evidence that they could treat McArdle s Many of these supplements are involved in the breakdown of fatty acids Fatty acids can be broken down to produce energy which provides energy for the second wind This is an alternative method to produce energy than glycolysis the breakdown of glycogen to glucose I imagine that people would take these supplements in the hope of improving the second wind phenomenon However there is no clinical evidence for taking any of these supplements These supplements include 7 2 1 Vitamins Note for vitamin B6 see section 7 1 2 B12 Vitamin B12 is a water soluble vitamin essential for the brain and nervous system and also in formation of blood It is also involved in production of fatty acid and energy The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 91

Biotin is a water soluble B complex vitamin Biotin contributes to breakdown of fatty acids and the amino acid leucine Biotin is also involved in gluconeogenesis Vitamin D is a fat soluble vitamin Its principal role is bone growth and maintaining bone strength 7 2 2 Amino acids Note for branched chain amino acids see section 7 1 1 2 L Alanine an amino acid L Carnatine made from a compound of several amino acids Carnatine is involved in breaking down of fatty acids to produce energy 7 2 3 Coenzyme Q 10 CoQ10 also known as ubiquinone or ubidecarenone CoQ10 is is a naturally occurring compound that is involved in generating energy ATP during aerobic respiration Sweetman 2009 Coenzyme Q 10 CoQ10 is also known as ubiquinone or ubidecarenone There is no published data or any published hypotheses that CoQ10 supplements are of any benefit to McArdle people The only relevant mention of CoQ10 was in conjunction with statin treatment see 12 1 1 for further discussion of statins Statins can reduce the levels of CoQ10 in the blood Sweetman 2009 It was hypothesised that taking CoQ10 at the same time as statins may protect muscles against damage caused by the statins However research to date has been inconclusive Molyneaux et al 2008 describe a trial they carried out People unaffected by McArdle disease took a statin called simvastatin with or without CoQ10 but there was no significant difference in the amount of muscle damage seen in the two groups CoQ10 supplement is mentioned as an aside in report by Kono et al 1984 They were testing the effect of glucagon on a McArdle woman aged 26 years old She had been taking CoQ10 supplements for the past year and had felt these had led to improvement of her symptoms The authors did not test whether CoQ10 had any effect on McArdle s symptoms There have been no clinical trials of CoQ10 supplements as a treatment for McArdle disease 7 2 4 Medical advice should be obtained before commencing use of a supplement IMPORTANT All supplements should be discussed with your family doctor before you begin taking them Medical advice should be obtained before commencing use of a supplement This is for a variety of reasons An excessive level of some supplements may restrict absorption of other nutrients or vitamins leading to a deficiency Some supplements can interact with prescription or herbal medicines drugs It is possible to overdose on some supplements especially those which are fat soluble and this could have health risks Page 92 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Recommended reading Pharmacological and nutritional treatment for McArdle disease Glycogen Storage Disease type V Quinlivan R Martinuzzi A Schoser B 2010 Cochrane Database of Systematic Reviews It is also useful to search online and see if there is an updated version Exercise Sport Nutrition Principles Promises Science Recommendations 2009 by Richard B Kreider Brian C Leutholtz Frank I Katch Victor L Katch Useful general information on several of the supplements described above Google free books The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 93

Page 94 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

8 The effect of age on the symptoms of McArdle disease Symptoms are not usually seen in babies with McArdle s although one case of a toddler with McArdle s has been reported McArdle children under the age of 5 years old often do not have classic McArdle symptoms and many have no difficulty with exercise Despite having no classic McArdle symptoms young McArdle children are likely to have high creatine kinase CK levels in the blood In a child who is suffering from muscle pain or difficulty with exercising high resting CK levels in the blood may be the first indication to suggest a possible diagnosis of McArdle s From around the age of 5 years and onwards McArdle children usually experience the classic McArdle symptoms of muscle pain muscle cramps myoglobinuria and difficulty with exercise These typical symptoms of McArdle disease continue to be seen in older childhood adolescence and adulthood Over the age of 40 some McArdle people have muscle wasting and weakness in the arms and trunk of the body The reasons for muscle wasting and weakness are not yet known but may be a normal part of ageing as it is usual for muscle wasting and weakness to occur in older people unaffected by McArdle s McArdle people do not usually become severely handicapped or need to use a wheelchair McArdle disease does not appear to affect lifespan and there are several published reports describing elderly McArdle people aged 70 80 years old Some older papers have reported rare forms of McArdle disease including a rare fatal infant form and a late onset form These papers were published many years ago before all the modern tests were available and it is therefore not possible to find out whether there is a scientific explanation for these such as a second disease which was fatal Recent studies of large numbers of McArdle people have only described the classic form of McArdle disease and I believe this to be the only form of McArdle s The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 95

8 1 Are there several forms of McArdle s Historically is has been suggested that there may be several forms of McArdle disease which I have summarised these below as four forms 1 to 3 are outlined by Roubertie et al 1998 and 3 and 4 are outlined by Papadimitriou et al 1990 1 a rare fatal infant form 2 a milder form with delayed motor milestones limb muscle weakness and high CK 3 a classic form which begins in childhood with symptoms of difficulty in exercising and normal CK levels alternate with acute episodes of exercise intolerance 4 a late onset form which begins in adult life and leads to progressive muscle weakness Each of these forms is discussed in more detail below Personally I believe that only the classic form is genuinely McArdle disease It should be noted that no cases of the rare fatal infant form or milder form have been reported in the last ten years A criticism of the papers which reported these two forms is that they were performed before genetic testing for McArdle disease was possible The papers also do not make it clear if a second disease was tested for or excluded A great difficulty with these cases is that it is likely that no samples remain so it is not possible to carry out further tests on samples from these people to determine if they had been misdiagnosed If only the classic form is genuinely McArdle disease there is a risk that the other forms are perpetuated by published papers repeating old theories until they appear to be fact I suspect that modern clinicians and experts on McArdle disease now also believe that only the classic form is McArdle disease as there is no mention of any of the other forms in the recent papers published about McArdle s such as papers by Quinlivan and Vissing 2007 and Lucia et al 2008a In my opinion if a survey of all McArdle people was conducted 98 of them would have the classic form A possible explanation for the remaining 2 would be that they either have double trouble see section 9 6 1 or have been misdiagnosed and actually have another similar muscle disease see section 2 5 8 1 1 A rare fatal infant form There have only been three cases reported Roubertie et al 1998 Two of these died at 13 weeks and 16 days respectively All three of the cases suffered from respiratory failure i e were not able to breathe But there were other unusual factors One of the children had general weakness one was quadriplegic not able to move any limbs and one was a child from consanguineous parents Consanguineous means that the parents were highly related e g brother and sister or first cousins See section 3 3 6 One possible explanation for these unusual cases of infant fatality is that the child inherited McArdle disease and also inherited a second recessive disease this is known as double trouble see section 9 6 and it was the effect of the second disease which was fatal It is well known that consanguineous parents often lead to an increased likelihood of the child having a recessive disease There is a report of an infant girl who died at 5 months of age She had mutations in both copies of the PYGM gene and also in both the copies of the deoxyguanosine kinase dGK genes Mancuso et al 2003 Her Moroccan parents were related they were first cousins Deoxyguanosine kinase is an enzyme involved in producing energy in the mitochondria Page 96 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

with the genetic information also provided by mitochondria Mitochondrial DNA depletion syndrome caused by lack of deoxyguanosine kinase is u sually fatal This child had liver failure which is not seen with McArdle disease but is commonly seen with mitochondrial DNA depletion syndrome The mutation in the deoxyguanosine kinase dGK gene was a 4bp deletion of GATT at 763 It is relevant to note that Salviati et al 2002 had reported a child with this mutation who did not have McArdle s who began to have symptoms at the age of 2 months and died at the age of 5 months It is frustrating that Mancuso et al 2003 did not mention this in their paper and instead suggested that the 5 month old child may have died from the fatal infant form of McArdle s In my opinion it is much likely that it was the mutation in the deoxyguanosine kinase dGK which was fatal It is also possible that a child with McArdle disease could die of a completely different cause which may not be inherited There is a case of a 3 month old child with McArdle disease who died of sudden infant death syndrome SIDS el Schahawi et al 1997 Unlike the other children mentioned above who died shortly after birth her parents did not notice any muscle weakness SIDS occurs to adults and children unaffected by McArdle disease and the cause of SIDS is still not known Shaffer 2009 El Schahawi et al 1997 suggest that McArdle disease could be a predisposing factor for SIDS But I disagree as a single case of a McArdle s child who died from SIDS is not sufficient evidence to suggest that the SIDs and McArdle disease could be related 8 1 2 A milder form with delayed motor milestones limb muscle weakness and high CK There have only been two cases of this reported Roubertie et al 1998 One child had delayed motor milestones took longer to crawl sit up walk than most children limb muscle weakness and high CK levels The fact that it is mentioned in only two published reports suggests that delayed motor milestones are not typical symptom of McArdle disease Therefore a possible explanation is that this child did not have McArdle disease and it was as case of misdiagnosis These symptoms are all characteristics of other muscle diseases such as congenital myopathy with type 1 fiber predominance CMT1P Na et al 2006 or Duchenne muscular dystrophy Dubowitz and Sewry 2007 8 1 3 A late onset form which begins in adult life and leads to progressive muscle weakness There are several explanations for this One explanation is that this is seen in carriers of McArdle s who have a second muscle disease If the second muscle disease makes the muscles weaker this may trigger symptoms of McArdle disease An example of this could be the case described by Papadimitriou et al 1990 who described a man who developed McArdle s symptoms at the age of 30 years and who was a carrier he had 25 functional muscle glycogen phosphorylase Further details about this case are given in section 9 7 A second explanation is if a McArdle person had managed to have a lifestyle which was ideal for McArdle s and had avoided symptoms without even knowing they had McArdle s For example an office worker would not have needed to do intense activity on a daily basis They may not notice McArdle s symptoms until their muscles begin to grow weaker as part of getting older Tunzun et al 2002 said that Many life long McArdle s sufferers are finally diagnosed in their 50 s and 60 s It is now believed that many cases may go unnoticed Makary et al 2008 reported a man who was The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 97

diagnosed with McArdle s at the age of 65 years old His symptoms seemed to have got slightly worse with age but he did not seem to have had any contractures or severe symptoms He was not diagnosed until he had treatment with Lipidor a statin which seems to have made his McArdle s symptoms worse Harris et al 1985 reported a woman who was diagnosed with McArdle s at the age of 71 years She had myoglobinuria and had muscle breakdown when having very little exertion She had high CK levels Harris and Dowben 1985 She had led a sedentary lifestyle She had no functional muscle glycogen phosphorylase in her muscles Her parents were first cousins consanguineous parents see section 3 3 6 Her mother had severe muscle cramps when she exercised and her sister had very high CK and muscle cramps after strenuous exercise Harris and Dowben 1985 It is unusual to have several family members mother sister and niece all with symptoms of high CK and muscle cramps Wolfe et al 2000 described a man who was diagnosed with McArdle s at the age of 73 He had no history of exercise causing muscle cramps muscle pain or myoglobinuria He had creatine kinase levels which were elevated serum lactate did not rise when he did an ischaemic forearm test and he had vacuolar myopathy with no functional muscle glycogen phosphorylase A third explanation could be that the symptoms were present but that the McArdle person did not consult a family doctor or that a family doctor did not recognise the symptoms As McArdle disease is relatively uncommon some family doctors may not realise that their patient has McArdle s The difficulties that patients may find in obtaining a diagnosis are discussed further in section 10 3 2 Apart from the suggestions given above I find it hard to explain how late onset could occur since McArdle people will have had a lack of muscle glycogen phosphorylase since a baby and therefore I would expect symptoms to have been present since childhood 8 2 The classic form In this classic form of McArdle s the principle symptoms are difficulty with exercise and relatively normal CK levels between acute episodes of exercise intolerance 8 2 1 The classic form of McArdle s from baby to toddler Ito et al 2003 claimed to have found the youngest clinically diagnosed patient with McArdle disease confirmed by muscle biopsy in a 14 month old girl She was admitted to hospital because of repeated high CK levels of 5340 U l 17 700 U l and 10 17U l as well as a fever pyrexia She was diagnosed with McArdle s after a muscle biopsy showed an absence of muscle glycogen phosphorylase although it was noted that there was no obvious glycogen storage in the muscle cells Other muscle diseases were ruled out This McArdle s girl offered a rare opportunity to get a recent history of a McArdle s baby and the authors provide many useful details about the baby and her growth The baby was born at term after an uneventful pregnancy She was capable of visual tracking and social smiling within 2 months of birth head control at 4 months sitting unsupported at 6 months rolling at 6 7 months walking with support by 12 months and walking unaided at 13 months She was beginning to speak at the age of 14 months Both her development and her physical growth were standard for her age This McArdle s girl did not demonstrate any of the delayed motor milestones described in the milder infant form section 8 1 2 Page 98 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

8 2 2 The classic form of McArdle s in childhood A summary of published reports of McArdle s children is provided in Table 8 1 Several criticisms could be made of the information presented in this section There is a lack of data as at present very few studies of children with McArdle s have been performed Further studies are needed to determine whether the children studied are representative of McArdle s in childhood As some of these publications are up to 30 years old the mutations were not identified in some cases and did not have the benefit of the knowledge of McArdle s which has been gained since then If we assume that the information in Table 8 1 is reliable it may be possible to draw some conclusions about children with McArdle s From the very limited information available it could be suggested that up to the age of 5 or 6 children do not have as many symptoms of McArdle s However Perez et al 2009 found that a 4 year old child had a raised resting CK 2656 U l despite being asymptomatic Since children may not be able to speak clearly or have a wide vocabulary until the age of 5 one possibility is that children under 6 years old are able to experience McArdle symptoms but are not able to put them into words It is possible that younger children have a slightly different metabolism for example newborn babies have brown fat which provides a source of energy and this may explain why some children do not appear to have McArdle symptoms Perez et al suggested that children may get energy from other methods rather than glycogenolysis Typical symptoms of classic McArdle s in children from birth to the age of 5 or 6 onwards summarised from Table 8 1 May be completely asymptomatic with no physical signs of McArdle disease Do not have delayed motor milestones May have raised resting CK levels Typical symptoms of classic McArdle s in children from the age of 5 or 6 o nwards to adulthood summarised from Table 8 1 Difficulty in exercising Raised resting CK levels Muscle cramps Muscle pain Myoglobinuria Extreme exertion chopping wood or swimming can cause myalgia muscle pain myoglobinuria and potentially kidney failure These symptoms summarised in Table 8 1 and the anecdotal reports from McArdle adults recollecting their childhood I think strongly suggest that the classic form is the most common and normal childhood form of McArdle s The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 99

However children with McArdle s also sometimes do not have the same symptoms as adults as the second wind may be less noticeable or absent Perez et al 2008 Perez et al 2009 and some McArdle s children are able to sprint Perez et al 2009 reported that child C had a second wind phenomenon but that the other three McArdle s children A B and D had a much less noticeable second wind than is usually seen in McArdle s adults Perez et al 2008 reported that the child H aged 8 9 did not experience second wind he didn t feel the early tiredness rapid heart rate or breathlessness which adult McArdle people get before the second wind begins Perez et al 2009 noted that the second wind phenomenon may not have been seen if the children were not asked to exercise hard enough when tested They also noted that the heart rate of the youngest child child A during exercise was not as high as would have been expected suggesting that the child was not exercising enough to trigger the second wind response Williams et al 1985 made the surprising observation that two of the McArdle s children J and K were able to sprint well for short distances without discomfort but unfortunately the authors did not give measurements of the distances 8 2 2 1 Diagnosis of children with McArdle s Based upon the information available this suggests that raised CK levels in children under the age of Child 6 even in the absence of other symptoms of McArdle s could indicate that they may have McArdle s For children above the age of 6 most of the symptoms outlined above are similar to those experienced by McArdle s adults A Since children with McArdle s do not seem to have all the classic symptoms seen in adults it is recommended that a high CK level when resting should be the first clue that a child has McArdle s and this should be followed by genetic testing rather than muscle biopsy if at all possible Perez et al 2009 B Unaffected C D E Page 100 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Male Diagnosed by 31P MRS the pH in the muscle cells did not fall below 6 94 during exercise The McArdle Disease Handbook Version 1 1 1 5 E Struggled to exercise since the age of about 6 onwards Resting CK was 2855U l R50X homozygous Struggled to exercise since the age of about 6 onwards Resting CK was 1500 U l Kathryn Birch Diagnosed by 31P MRS the pH in the muscle cells did not fall below 6 94 during exercise R50X homozygous No functional muscle glycogen phosphorylase in muscle biopsy Mutations not known Carrier of McArdle disease the faulty PYGM gene had the R50X mutation Struggled to exercise since the age of about 6 onwards Resting CK 829 U l A and B were siblings Page 101 The McArdle Disease Handbook Version 1 1 1 Not stated Female Male Did not appear to have symptoms NOTE The lack of McArdle symptoms might have been due to the child being too young to describe symptoms of muscle pain or if one or both parents were misdiagnosed the child might have in fact only been a carrier Both parents had McArdle s E and F were siblings 17 No functional muscle glycogen phosphorylase in muscle biopsy Mutations not known Female R50X homozygous Did not complain of any symptoms of McArdle s but had a high resting CK 2656U l Child A was able to run around and keep up with his friends in physical education classes and the amount of oxygen he needed during exercise his VO2 peak was normal for his age and gender A and B were siblings Perez et al 2009 Kathryn Birch Page 101 Gruetter et al Did not appear to have symptoms NOTE The lack of McArdle symptoms might have been due to the child being 1990 too young to describe symptoms of muscle pain or if one or both parents were misdiagnosed the child might have in fact only been a carrier Both parents had McArdle s E and F were siblings Struggled to exercise since the age of about 6 onwards Resting CK was 1500 U l Struggled to exercise since the age of about 6 onwards Resting CK was 2855U l Perez et al 2009 Perez et al 2009 Publication Resting CK level was 99 U l Unaffected sibling of A and B Symptoms D Resting CK level was 99 U l Unaffected sibling of A and B R50X homozygous Carrier of McArdle disease the faulty PYGM gene had the R50X mutation Female R50X homozygous 14 R50X homozygous Method of diagnosis PYGM mutations C 6 Not stated Unaffected 5 Perez et al 2009 Female Struggled to exercise since the age of about 6 onwards Resting CK 829 U l A and B were siblings 17 12 Male B 14 Perez et al 2009 Female Did not complain of any symptoms of McArdle s but had a high resting CK 2656U l Child A was able to run around and keep up with his friends in physical education classes and the amount of oxygen he needed during exercise his VO2 peak was normal for his age and gender A and B were siblings 6 4 Female A Symptoms 12 Method of diagnosis PYGM mutations Male Gender 4 Age years Gender Child Age years

9 8 F G Female Page 102 He had been performing quite vigorous exercise chopping Delibas et al wood He was admitted to hospital with myoglobinuria 2008 and muscle pain Myoglobinuria had led to kidney failure He also had a CK level of 33 766 U l He required dialysis to treat the kidney failure Perez et al From the age of 5 the boy had had general muscle pain muscle weakness and struggled to exercise At the age of 8 2008 he was admitted to hospital with severe muscle pain myalgia muscle weakness myoglobinuria hyperthermia and high creatine kinase levels 4270 U l after swimming No functional glycogen phosphorylase in muscle biopsy R50X homozygous From the age of 5 the boy had had general muscle pain Pe muscle weakness and struggled to exercise At the age of 8 200 he was admitted to hospital with severe muscle pain myalgia muscle weakness myoglobinuria hyperthermia and high creatine kinase levels 4270 U l after swimming No functional muscle glycogen phosphorylase in muscle biopsy Symptoms of exercise intolerance since the age of 4 difficulty walking uphill CK of 1500 IU l and 3234 IU l following contraction of fingers No functional muscle glycogen phosphorylase in muscle biopsy Slow walking particularly uphill which caused leg cramps W CK initially 7548 IU l No rise in blood lactate occurred Ho when an ischaemic forearm test was performed No functional muscle glycogen phosphorylase in muscle biopsy Difficulty walking needed frequent rests No rise in blood lactate occurred when an ischaemic forearm test was performed CK level was 650I U l Kathryn Birch 8 10 10 I J K 8 The McArdle Disease Handbook Version 1 1 1 Page 102 Kathryn Birch Williams and Hosking 1985 The McArdle Disease Handbook Version 1 1 1 Difficulty walking needed frequent rests No rise in blood lactate occurred when an ischaemic forearm test was performed CK level was 650I U l No functional muscle glycogen phosphorylase in muscle biopsy Williams and Hosking 1985 Female He had been performing quite vigorous exercise chopping De wood He was admitted to hospital with myoglobinuria 200 and muscle pain Myoglobinuria had led to kidney failure He also had a CK level of 33 766 U l He required dialysis to treat the kidney failure Slow walking particularly uphill which caused leg cramps Williams and CK initially 7548 IU l No rise in blood lactate occurred Hosking 1985 when an ischaemic forearm test was performed Low levels of functional muscle glycogen phosphorylase No functional muscle glycogen phosphorylase in muscle biopsy Reported having muscle cramps since the age of 5 Both parents had McArdle s E and F were siblings Female No muscle glycogen phosphorylase in muscle biopsy Symptoms of exercise intolerance since the age of 4 difficulty walking uphill CK of 1500 IU l and 3234 IU l following contraction of fingers Symptoms No functional muscle glycogen phosphorylase in muscle biopsy Method of diagnosis PYGM mutations Female Male Gruetter et al 1990 Low levels of functional muscle glycogen phosphorylase No functional glycogen phosphorylase in muscle biopsy R50X homozygous Male Publication Reported having muscle cramps since the age of 5 Both parents had McArdle s E and F were siblings Female No muscle glycogen phosphorylase in muscle biopsy Male Symptoms Male Method of diagnosis PYGM mutations Not stated Not stated Gender Gender H Age years Female Child ars Pu Gr 199 W Ho W Ho

14 Female The McArdle Disease Handbook Version 1 1 1 Male No functional muscle glycogen phosphorylase in muscle biopsy An accumulation of glycogen Described as an atypical case CK ranged from 127 U l to 11 520 U l normal was up to 70 U l Symptoms did not change between the ages of 12 and 15 Lazy since early childhood Persistent mild muscle weakness Never had cramp or muscle pain No functional muscle glycogen phosphorylase in muscle biopsy and reduced amount of phosphorylase was seen in enzyme activity test Enzyme activity was 0 32U g normal was 25 1 37 0U g Rapid walking caused muscle fatigue from the age of 6 onwards However able to get into second wind Had myoglobinuria twice Cycling caused muscle pains Ischaemic forearm test caused a contracture However a small rise in lactate was seen from 0 86 to 1 07mmol l R50X homozygous Exercise caused myoglobinuria Diagnosed by genetic analysis Muscle pain during exercise which disappeared after a rest Raised CK levels R50X and G205S Symptoms since the age of 5 Muscle tightness or seizing up if walking briskly for more than 300 metres or walking up a hill CK levels were not tested Female Male Male R50X and G205S Diagnosed by genetic analysis R50X homozygous Publication Kristjansson et al 1994 Symptoms since the age of 5 Muscle tightness or seizing up if walking briskly for more than 300 metres or walking up a hill CK levels were not tested Miteff et al 2011 Muscle pain during exercise which disappeared after a rest Koenraads et Raised CK levels al 2011 Exercise caused myoglobinuria No functional muscle glycogen phosphorylase in muscle biopsy An accumulation of glycogen No functional muscle glycogen phosphorylase in muscle biopsy and reduced amount of phosphorylase was seen in enzyme activity test Enzyme activity was 0 32U g normal was 25 1 37 0U g Symptoms Male Method of diagnosis PYGM mutations Kathryn Birch The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 103 Table 8 1 Clinical features of children with McArdle disease information from published papers R50X homozygous means that in one person both copies of the PYGM gene have the R50X mutation 14 8 N Male Sengers et al 1980 12 Rapid walking caused muscle fatigue from the age of 6 onwards However able to get into second wind Had myoglobinuria twice Cycling caused muscle pains Ischaemic forearm test caused a contracture However a small rise in lactate was seen from 0 86 to 1 07mmol l Male P 12 M 8 Chiado Piat et al 1993 Male Described as an atypical case CK ranged from 127 U l to 11 520 U l normal was up to 70 U l Symptoms did not change between the ages of 12 and 15 Lazy since early childhood Persistent mild muscle weakness Never had cramp or muscle pain 12 12 12 L Symptoms Male Method of diagnosis PYGM mutations 12 Gender Gender O Age years al features of children with McArdle disease information from published papers R50X homozygous means that in one person e the R50X mutation Child Age years Page 103

8 2 3 McArdle s in adulthood middle age Most McArdle people experience McArdle s symptoms in childhood Quinlivan et al 2007 2010 said that 84 of 45 McArdle people recalled symptoms before 10 years of age although many were not diagnosed until adulthood Only about half 51 were diagnosed by the age of 30 with the remaining 49 being diagnosed when older than 30 Most of the classic symptoms of McArdle s are discussed in detail in other sections of this Handbook including the typical symptoms listed below Typical symptoms and features of classic McArdle s in adulthood middle age are Muscle pain upon exercising Contractures Raised creatine kinase levels Second wind 8 2 4 McArdle s in older age As discussed by Perez et al 2008 historically McArdle people were recommended to have a sedentary lifestyle to avoid the risk of exercise causing rhabdomyolysis Elderly McArdle people are likely to have received this advice They may have had a sedentary lifestyle since childhood or whenever they were diagnosed In terms of lifestyle Perez et al say that it is well known that if children get into the habit of exercising when young they are more likely to continue to exercise when older Conversely if McArdle people were advised not to exercise many years ago they are likely to have continued this trend It should be noted that the recommendations for McArdle people have now changed and a moderate level of exercise is now recommended see section 4 2 2 Perez et al 2006 reported the case of a 78 year old male with McArdle disease who was able to do very little exercise when first tested which he suggested was the result of a very sedentary lifestyle At the time the paper was written there had not been any studies performed to assess the amount of exercise which elderly people with McArdle s were able to do The authors suggested that one reason why this study had not been conducted was because of the risk of discomfort and rhabdomyolysis They gave the 78 year old man 660ml of solution which contained 75g of sucrose They gave him a 10 minute warm up period before testing his exercise capacity using a cycle ergometer test see section 2 3 1 2 They also measured the amount of oxygen he breathed in called the VO2 peak Based upon this single McArdle person who had led a very sedentary lifestyle the authors of study suggest that it is likely that elderly McArdle people have a decrease in their VO2 peak However they also state that research on elderly people in general mostly those who do not have McArdle s suggests that elderly people are able to safely learn how to exercise and increase their ability to exercise Although this report is interesting it must be emphasised that a single case study is not considered a large enough sample size to base medical advice This study would have been greatly improved if they had set a basic exercise programme for the patient and then tested him again a year later to see if he was fitter and better able to exercise Page 104 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

8 2 4 1 Muscle wasting and muscle weakness is a symptom of McArdle s which may develop or increase in older age Case studies of several elderly McArdle people have been reported Lucia et al 2008 described an elderly McArdle person who was then 81 this was the same person described when aged 78 by Perez et al 2006 This person had lived a sedentary lifestyle since childhood In older age this person had quite severe exercise intolerance and had proximal muscle atrophy and fixed weakness Pourmound et al 1983 described a 76 year old McArdle man whose symptoms began at age 74 years with sudden onset of proximal muscle weakness and fatigability Electromyography showed nerve activity and the muscle cells looked like there was inflammatory muscle disease The diagnosis of McArdle disease was made by performing tests on a muscle biopsy an abnormal ischemic lactate test and absence of functional muscle glycogen phosphorylase The amount of muscle wasting and weakness seen in McArdle people appears to increase with age Amato 2003 Nadaj Pakleza et al 2009 Quinlivan et al 2010 reported that 24 of 45 McArdle people had muscle hypertrophy increased muscle size and 16 all aged over 40 years old had mild upper limb and trunk weakness Nadaj Paleza et al 2009 found that 10 of 80 McArdle people all aged over 40 had proximal fixed muscle weakness and that 37 5 of the McArdle people aged over 40 years old had muscle weakness There are many possible explanations for muscle weakness It is not clear whether activity in younger life has an effect upon the development of muscle wasting and weakness One possibility is that a sedentary inactive lifestyle means that the muscles are not used and become weak and waste away An opposite possibility is that excessive exercise when younger could cause repeated d amage and that eventually the muscles become unable to repair themselves leading to weakness and wastage Voduc 2004 suggested that fixed muscle weakness could be caused by repeated muscle damage and loss of skeletal muscle fibres due to rhabdomyolysis Schotland et al 1965 investigated muscle biopsies from two McArdle people and suggested that glycogen accumulation may disrupt the structure of the muscle and this could be one of the causes of permanent weakness that has been observed in the older people with McArdle disease Another possibility is that muscle weakness may be at least partially caused by damaged muscle being replaced as fat De Kerviler et al 1996 Nadaj Pakleza et al 2009 carried out a scan which showed fatty infiltration in the shoulder and pelvic girdle muscles An alternative possibility is that a different gene a phenotype modulator may have an effect upon the strength of the muscle and would explain why some but not all McArdle people develop weakness in older age This gene may not have been identified Phenotype modulators and other factors which affect the severity of McArdle s symptoms are discussed in section 9 It should be remembered that muscle wastage and weakness with older age is not a specific symptom of McArdle s Weakness and wastage in the muscles with age is common in the population unaffected by McArdle s The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 105

8 2 5 Will I end up in a wheelchair The quick answer is no most McArdle people do not need to use a wheelchair In McArdle disease only a few patients were reported who were severely handicapped and complained of generalized pain with minimal exercise Rommel et al 2006 McArdle people who use a wheelchair may have McArdle s plus a second muscle disease see section 9 6 on double trouble or may not have McArdle s they may have been misdiagnosed and may actually have a different disease They may also be people whose muscles have got very weak due to lack of exercise and where exercise now results in severe muscle damage and weakness so they are in a negative spiral of muscle weakness anecdotal Some people who are unaffected by McArdle s require the use of a wheelchair in old age or for other reasons If a McArdle person requires the use of a wheelchair it is likely to be for reasons unrelated to McArdle disease 8 2 6 Does McArdle disease affect lifespan There is no published information on whether McArdle s has any effect upon lifespan how long you live There are several published reports of elderly McArdle people including a 76 year old McArdle man Pourmand et al 1983 a 78 year old McArdle man Perez et al 2006 and an 81 year old McArdle person Lucia et al 2008a The fact that there are many reports of elderly McArdle people suggests that McArdle s does not have any effect upon lifespan Although in general McArdle disease does not appear to have any effect upon life expectancy there are rare reports where people have died for reasons where McArdle disease may have been a factor It has been reported that fatalities have occurred to McArdle people carrying out activities such as swimming or climbing where muscle weakness has caused a fatal accident source http www specialisedservices nhs uk library 23 Service_Specification___McArdles_Disease pdf There is also a press report of death where intensive exercise had led to acute kidney failure and cardiac failure a heart attack source http www leadertelegram com people obituaries article_3cf469d9 93a3 55ad b0ad 5783477c2eb9 html These reports highlight the importance of seeking medical attention if rhabdomyolysis muscle damage occurs and of avoiding situations such as rock climbing or swimming where muscle weakness or fatigue could be dangerous Page 106 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

9 Differences in severity of symptoms between people The most obvious factor which might explain differences in the severity of symptoms is the amount of muscle glycogen phosphorylase which a person has In general the more functional muscle glycogen phosphorylase a person has the better their ability to exercise Unaffected people who have normal levels of muscle glycogen phosphorylase are able to exercise easily carriers who have approximately half the amount of muscle glycogen phosphorylase are also able to exercise normally and do not have symptoms of McArdle disease Very rarely some McArdle people have a mutation which enables the enzyme to work a little McArdle people with even a very low small amount of functional muscle glycogen phosphorylase were able to exercise more easily than typical McArdle people Almost all mutations in the PYGM gene result in a complete absence of functional muscle glycogen phosphorylase so almost all McArdle people do not have any functional muscle glycogen phosphorylase It would therefore be expected that all McArdle people would have similar symptoms But this does not appear to be the case some McArdle people report much more severe McArdle s symptoms than others Other proteins in the body which are unrelated to muscle glycogen phosphorylase may have an effect upon symptoms For example proteins which help the muscle cells take up glucose or produce energy more efficiently could have an effect on the severity of McArdle s How well these proteins work can vary from person to person Interestingly it has been found that some of these proteins have an effect on the severity of McArdle symptoms in women but not in men McArdle symptoms can be more severe if the McArdle person has another muscle disease or has a different disease which affects their ability to exercise or to get energy from food they eat Carriers of McArdle disease do not usually have symptoms of McArdle disease but in rare cases a second disease which affects the muscles may result in the carrier having McArdle symptoms One study of McArdle women found that there were two different types of pain pain caused by exercise or constant chronic pain Women who had pain caused by The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 107

exercise would cope by focussing on a completing a task whereas for women with permanent pain the pain had a greater impact on the daily life work and social activity Page 108 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

9 1 The amount of functional muscle glycogen phosphorylase is an important factor which determines the severity of symptoms 9 1 1 The amount of functional enzyme determines whether carriers of the PYGM mutation have symptoms of McArdle disease McArdle carriers do not normally have symptoms of McArdle disease as they have some functional glycogen phosphorylase Andersen et al 2006 compared McArdle patients carriers and unaffected people during exercise Carriers had normal oxidative capacity and lactate responses which were identical to controls They were therefore able to exercise normally and did not have symptoms of McArdle disease an observation already reported by doctors treating McArdle people Quinlivan and Vissing 2007 An exception where a carrier had McArdle s symptoms is discussed in section 9 7 Carriers of the PYGM mutation have intermediate levels approximately half the amount of muscle glycogen phosphorylase enzyme activity compared to unaffected people The amount of functional muscle glycogen phosphorylase in carriers has been reported as 25 45 Bogusky et al 1986 and 30 45 Manfredi et al 1993 that of unaffected people It is likely that this amount of functional muscle glycogen phosphorylase is sufficient to enable carriers to exercise in a similar way to unaffected people 9 1 2 Different mutations do not correlate to differences in severity of symptoms The most obvious explanation for differences between McArdle people would be that different mutations in the PYGM gene could lead to differences in severity of symptoms However from a biochemical point of view this idea does not work as most mutations result in a complete absence of functional muscle glycogen phosphorylase The exception is the small number of McArdle people who have a very low residual level of functional muscle glycogen phosphorylase These are discussed further in section 9 1 4 If differences in the mutation the genotype had an effect upon the physical effect of those genes on the body including severity of symptoms the phenotype it could be described as a genotype phenotype relationship No clear genotype phenotype relationship has been seen despite studies of large numbers of people with McArdle s Martin et al 2001 DiMauro et al 2002 Deschauer et al 2007 Delmont et al 2008 9 1 3 Rarely some McArdle people have low levels of functional muscle glycogen phosphorylase There have also been rare reports of McArdle people with functional muscle glycogen phosphorylase One person had enzyme with 13 of normal activity and three cases were 3 active compared to normal levels Martinuzzi et al 1996 One person with 2 of functional muscle glycogen phosphorylase was described by Andersen et al 2006 Delibas et al 2008 and Delmont et al 2008 each reported a McArdle person with just detectable functional muscle glycogen phosphorylase Information about the mutations of these McArdle people with low levels of functional muscle glycogen phosphorylase would be very informative 9 1 4 Even a very small amount of functional muscle glycogen phosphorylase improves the ability of McArdle people to exercise Quinlivan and Vissing 2007 reported research by Haller that McArdle people with even a very low level of functional muscle glycogen phosphorylase 1 2 5 had much higher oxidative capacity were able to get more energy from food and able to exercise more easily Vissing et al 2009 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 109

reported two McArdle people with unusually high exercise capacity The two people had either R50X or G205S on one copy of the PYGM gene and novel splice mutations in introns 3 IVS3 26A G c 425 26A G and 5 IVS5 601G A c 856 601G A For more information about different types of mutations see section 3 2 4 It seems that these splice mutations allowed some functional muscle glycogen phosphorylase to be made in the muscles of these McArdle people which allowed them to exercise more easily than typical McArdle people These unusual McArdle people were able to reach a peak workload 2 fold higher than typical McArdle patients and oxygen uptake was more normal The authors claimed that this was the first published evidence of a relationship between the mutation and the ability of a McArdle person to exercise called a genotype phenotype relationship This evidence suggests that even low levels of functional muscle glycogen phosphorylase can lead to an improved ability of the McArdle person to exercise 9 2 Raised levels of cytokines may cause low level inflammation in McArdle people Cytokines are small proteins which are produced by almost all cells in the body Cells use cytokines as a way to communicate either with neighbouring cells or throughout the body if the cytokines are carried in the blood Chemokines are a sub group of cytokines and are also small proteins produced by cells Some chemokines are used by cells to create an immune or inflammatory response Cells can release chemokines during infection by bacteria or viruses which attracts cells of the immune system to the location to fight the cause of the infection Information on cytokines and chemokines is summarised from Janeway 2001 Lucia et al 2008b studied the levels of many cytokines and chemokines in both McArdle people and in unaffected people before and after exercise In McArdle people Lucia et al found raised levels of several cytokines tumor necrosis factor TNF interleukin IL 1ra IL 10 IL 12 and IL 17 They also found that McArdle people had a higher level of neutrophils Neutrophils are cells which are part of the immune system Neutrophils are some of the first cells which are attracted by the release of cytokines during infection They also found that the amount of cytokine IL 6 which the authors say has an anti inflammatory effect was increased in both McArdle people and unaffected people after exercise The authors conclude that Our results suggest that McArdle disease is associated with low level systemic inflammation whereas appropriate exercise induces a significant increase in the anti inflammatory myokine IL 6 They suggest that this anti inflammatory effect may explain why frequent moderate exercise has been shown to improve symptoms in McArdle people Several criticisms of the study conducted by Lucia et al 2008b may be made These include the fact that they gave sucrose to the McArdle people but not to the unaffected control participants before exercise This means that it is not possible to be sure that the differences in cytokine levels were due to McArdle s rather than sucrose For example it may be that sucrose causes raised cytokine levels in people irrelevant of whether they have McArdle s or not Despite these criticisms Lucia et al found that the levels of many of the cytokines were higher in people with McArdle s This was a new discovery and it would be ideal for it to be repeated and confirmed by other researchers The authors of this study suggested since exercise may cause muscle damage in McArdle people the body might increase the amount of IL 6 in order to have an anti inflammatory effect I have an Page 110 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

alternative explanation an unproven theory why the amount of IL 6 may increase in McArdle people when exercising There may be an association between the amount of glycogen in exercising muscle cells and IL 6 production Exercise increases the amount of IL 6 in healthy athletes unaffected by McArdle s Cannon et al 1999 Robson Ansley et al 2007 IL 6 appears to be released into the blood by exercising muscles to stimulate the liver to break down stored glycogen and release energy via the bloodstream Pedersen 2001 Steensburg 2001 Raised IL 6 levels in McArdle people reported by Lucia et al may be due to the shortage of free glucose in the muscle cells Pedersen 2001 described an increase in production of IL 6 by muscle cells due to lack of glycogen in unaffected people However the same effect would occur in McArdle people as the glycogen can t be utilized and converted to glucose to provide energy In McArdle people IL 6 may be released by the muscle cells in an attempt to increase production of glucose by the liver Raised cytokine levels in McArdle people have several possible implications 1 Many McArdle people are misdiagnosed with an inflammatory muscle disease such as polymyositis which is often treated with steroids to reduce the inflammation section 2 5 1 If McArdle s is also an inflammatory muscle disease it is easy to understand how this misdiagnosis could occur 2 There appears to be a link between McArdle s and type II diabetes characterised by insulin resistance There is some evidence that the cytokine TNF and possibly the cytokine IL 6 could lead to insulin resistance see section 13 4 1 2 3 Studies suggest that approximately a third of McArdle people experience anxiety or depression at some point in their lives Rommel et al 2006 Quinlivan et al 2010 de Ridder et al 2008 say that raised levels of some cytokines can produce feelings of fatigue irritability demoralisation and may cause feelings of depression It is possible that the feelings of depression experienced by McArdle people could be related to increased levels of some cytokines At present none of these possible implications have been fully investigated or proven so the implications are speculative 9 3 Phenotype modulators genes other than PYGM may affect the severity of McArdle s symptoms The combination of genes which a person has is known as a genotype the physical effect of those genes on the body including severity of symptoms is known as a phenotype A phenotype modulator is a second gene which affects the phenotype of the first gene In a McArdle person the first gene is the PYGM gene being homozygous for mutations in the PYGM gene causes a person to have McArdle disease It is possible that there are one or more secondary genes which have an effect upon how severe the McArdle s symptoms are This second gene is not related to the PYGM gene Depending what form of the second gene a McArdle person has the severity of the symptoms could vary between McArdle people The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 111

Phenotype modulators are a possible explanation for why different McArdle people can have different symptoms Recent research has identified several genes which appear to be phenotype modulators It is logical that proteins encoded by other genes for example proteins which help the muscle cells take up glucose or produce energy more efficiently could have an effect on the severity of McArdle s Several researchers have looked at genes which may be phenotype modulators Rubio et al 2007 Rubio et al 2008 and Martinuzzi et al 2003 studied large numbers of McArdle people to try to find out which if any of these phenotype modulator genes could be having an effect upon the severity of McArdle s 9 3 1 Angiotensin converting enzyme In skeletal muscle cells the angiotensin converting enzyme ACE is involved in providing energy during exercise The ACE enzyme is encoded by the ACE gene There are two versions of the ACE gene each of which have slightly different genetic sequences a nd produce a slightly different form of the ACE enzyme The two versions are known as the I and the D form Each person inherits two copies of the ACE gene one from each parent A person may inherit two copies of the D version of the ACE gene DD two copies of the I version of the ACE gene II or one copy of each version DI In humans the D version has the most ACE enzyme activity and the I version has the least activity People unaffected by McArdle s who have the I version are thought to be able to take up more glucose from the bloodstream into muscle cells and seem to respond better to muscle training and aerobic conditioning Scientists therefore suggested that McArdle people with the I version of the ACE enzyme might find it easier to exercise and have fewer symptoms Two studies have now found that McArdle people with two copies of the D version of the ACE enzyme have the most severe symptoms McArdle people with one copy of the D version of the ACE enzyme have intermediate symptoms and McArdle people with two copes of the I version of the ACE enzyme had less severe symptoms Martinuzzi et al 2003 Rubio et al 2007 These results led to a further study by Martinuzzi et al in 2008 to test whether treatment with the ACE inhibitor Ramipril would improve McArdle s symptoms A peptide small protein called bradykinin causes blood vessels to enlarge dilate and blood pressure to become lower ACE enzyme is one of the enzymes which break down bradykinin If an ACE inhibitor drug such as Ramipril is taken less bradykinin will be destroyed leading to an overall increase in bradykinin This will have the effect of increasing the size of the blood vessels which may allow more blood to be pumped to the muscles bringing more glucose and fatty acids and oxygen to the muscle cells When treated with Ramipril a very small improvement in the ability to exercise was seen in McArdle people who had two copies of the D version of the ACE enzyme but not people who had one copy of the D version and one copy of the I version of ACE 9 3 2 Muscle adenosine monophosphate deaminase In skeletal muscle cells AMP deaminase is an enzyme which converts a molecule called adenosine monophosphate AMP to a molecule called inosine monophosphate IMP as part of a process called purine catabolism that produces energy within muscle cells The AMP deaminase enzyme is encoded by the AMPD1 gene Adenosine monophosphate deaminase deficiency AMDD is caused by mutation in the AMPD1 gene Most cases of AMDD are caused by the premature termination codon mutation written as Q12X In this mutation a single mutation in the genetic code changes the Page 112 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

code from c to t so that glycine amino acid is replaced by a premature termination codon This results in the production of an abnormally short enzyme which cannot function Mutations in AMPD1 gene are very common with MADD identified in approximately 2 of all muscle biopsy specimens tested by research labs Gross 1997 In many of these cases people with the Q12X mutation are asymptomatic Where people do have symptoms the symptoms of MADD are muscle weakness muscle pain and muscle cramps following exercise MADD is usually inherited in an autosomal recessive way where people only have symptoms of MADD if they have two copies of the AMPD1 gene which both have mutations People do not usually have symptoms of MADD if they are a carrier for the Q12X mutation However Rubio et al 2008 wondered whether McArdle people might have more problems with exercise if they were carriers for the Q12X mutation rather than having two normal copies of the AMPD1 gene with no mutations in either copy of the AMPD1 gene They studied 44 Caucasian McArdle people 23 males 21 females who had two normal copies of the AMPD1 gene or who were carriers for the Q12X mutation and compared their ability to exercise using an ergometer test No differences were seen in McArdle men but in McArdle women being a carrier for the Q12X mutation of the AMPD1 gene was associated with reduced aerobic capacity 9 3 3 Myostatin Myostatin is a protein which helps to regulate and control skeletal muscle growth and may also affect muscle repair Myostatin is also known as growth differentiation factor 8 and is encoded by the GDF 8 gene It may therefore have an effect upon the strength and ability of muscle to repair itself following damage Normally myostatin has a negative effect upon skeletal muscle growth A mutation like the K153R missense mutation can stop myostatin being able to function At present the effect of the K153R mutation is not known but one possibility is that having the mutation could enable an increased amount of muscle growth which could increase muscle strength In women unaffected by McArdle s those with the K153R mutation have lower muscle strength than those without the mutation Gonzalez Freire et al 2009 found McArdle s women with the K153R mutation in the myostatin gene had worse McArdle s symptoms than McArdle s women who did not have the mutation 9 3 4 actinin 3 actinin 3 is a protein which is the main component of skeletal muscle It has a role in generating muscle contractions actinin 3 is encoded by the ACTN3 gene The R577X mutation introduces a premature stop codon which results in an absence of actinin 3 In people unaffected by McArdle s having the normal ACN3 gene may enable them to exercise for longer and elite sportspeople often have two normal copies of the ACN3 gene but studies are unclear and having the R577X mutation does not appear to be a disadvantage for most of the population Lucia et al 2007a found that McArdle s women with the R577X mutation were able to exercise better when tested using a cycle ergometer than those with a normal copy of the ACTN3 gene but the presence or absence of the mutation had no significant effect in McArdle s men Rubio et al 2007 also looked at whether mutations in ACN3 had any effect on severity of McArdle s symptoms They did not find any effect but did not separate the data for men and women The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 113

9 3 5 Peroxisome proliferator activated receptor coactivator 1 Peroxisome proliferator activated receptor coactivator 1 is a protein which is encoded by the PPARGC1A gene Peroxisome proliferator activated receptor coactivator 1 is involved in regulating the expression production of proteins involved in generating energy within the cell As a missense mutation G482S had been shown to improve aerobic capacity in people unaffected by McArdle s Rubio et al 2007 looked at whether this gene might affect the severity of McArdle s symptoms The results did not show that this gene had any effect on severity of McArdle s symptoms but they did not separate the data for men and women 9 4 There is a difference in the amount and type of pain felt by different McArdle people Some McArdle people have constant and permanent chronic pain Other McArdle people only have exercise induced pain or occasionally experience muscle pain after exercise if some muscle damage has occurred Rommel et al 2006 studied 24 McArdle people They asked many questions to determine whether McArdle people only had pain caused by exercise or whether they had permanent pain They found the majority of McArdle people who had permanent pain were women 8 of the 24 McArdle people had permanent pain and of these 7 were women There was only one man with permanent pain so they used the women to compare those with permanent pain with those with exercise induced pain For the women with permanent pain the pain had a greater impact on the daily life work and social activity In contrast where women principally had exercise induced pain their McArdle s symptoms had much less effect upon their daily life work and social activity They found that those with permanent pain felt more fatigue and tried harder to avoid pain However differences regarding depression and pain related help hopelessness were not significant Differences in the type or level of pain felt were not related to which mutation was in the PYGM gene or which version of the ACE gene the McArdle people had Rommel 2006 Rommel et al 2006 found that women who had exercise induced pain seemed to ignore the pain by endurance coping making sure they finished projects they started even if in pain and not resting as often They tried to ignore and play down any pain they experienced On the other hand women who had permanent pain seemed to feel that the pain was greater and worry about it They tried to avoid any activities which would cause pain It is not obvious whether there was an original difference between the women who had exercise induced pain or permanent pain or whether the difference was due to differences in attitude and different methods of coping with pain I inferred from the report that women who had exercise induced pain found that it had less effect upon their lifestyle than those who had permanent pain Women with permanent pain found that it had a greater effect upon their general activity and caused sleep disturbance and fatigue The authors suggest that regular moderate exercise may be a better way to cope with the symptoms of McArdle s than avoiding exercise The authors do point out that this study was limited by the small number of participants 24 McArdle people and a larger scale study would generate more useful information The authors suggest that Further studies should also address the question if these subgroups people with permanent pain versus people with exercise induced pain respond differently to therapeutic strategies like glucose substitution pain medication or regular moderate aerobic exercise Page 114 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

9 5 Gender has an effect on phenotype modulators and the severity of McArdle s symptoms Some studies suggest that McArdle women may experience more severe symptoms than McArdle men Among the middle aged patients whom we studied proximal muscle wasting and weakness was more frequent in women than in men in some cases the severity was such that the patients had to use an electric toothbrush as they easily became fatigued when brushing their teeth manually In addition the few adult patients in whom respiratory muscles have been shown to be affected have all been women Lucia et al 2008a As described above Rommel et al 2006 studied 24 McArdle people 12 men and 12 women They found that 8 of the 12 women had permanent pain whereas only 1 of the 12 men had permanent pain As outlined above researchers have found that in some cases the effects of phenotype modulators differ depending on gender In McArdle s women but not in men a mutation in the myostatin gene led to an increase in the severity of symptoms Gonzalez Freire et al 2009 Lucia et al 2007b found that the R577X version of the ACTN3 gene was associated with improved exercise capacity using a cycle ergometer in women with McArdle disease compared to the R577R version of ACTN3 but had no significant effect in men It is not clear why the effect of phenotype modulators could vary with gender but they may provide a partial explanation for several studies which suggest that McArdle women may be experience more severe symptoms than McArdle men 9 6 McArdle symptoms may be more severe if combined with another disease 9 6 1 McArdle symptoms can be more severe if combined with another muscle disease causing double trouble Rarely two muscle diseases may both occur in the same person causing double trouble Vladuitu et al 2000 looked at nine McArdle people and tested them for other muscle diseases myopathies Two of the McArdle people had a second muscle disease one had a Q12X stop codon causing myoadenylate deaminase AMPD deficiency and one had a S113L missense mutation causing carnitine palmitoyltransferase II CPT II deficiency They suggested that the first muscle disease lowers the threshold for manifestation of the symptoms Aguilera et al 2001 reported a person with biochemical evidence of McArdle disease heterozygous for R50X and also with a mitochondrial DNA point mutation in the cytochrome c oxidase subunit I COI gene Vockley et al 2000 reported one person who was diagnosed with McArdle disease as they only had 0 04 functional muscle glycogen phosphorylase and also was heterozygous for the S113L mutation in the CPTII gene Lucia et al 2007b reported a 29 year old woman with McArdle disease and myasthenia gravis for whom aerobic training significantly increased her exercise capacity The severity of symptoms will depend which two diseases the person has There is a report of an infant girl born to consanguineous Moroccan parents who died at 5 months of age She had homozygous mutations in both the PYGM and the deoxyguanosine kinase dGK genes Mancuso et al 2003 see section 8 1 1 Pulur et al 2009 reported a man who started to have difficult with exercise like walking upstairs from the age of 14 He also had consanguineous parents His muscle weakness was much more severe than that usually seen in McArdle people and he was subsequently diagnosed with both calpainopathy and McArdle disease Calpainopathy is an The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 115

autosomal recessive limb girdle muscular dystrophy LGMD2A caused by mutations in the gene encoding calpain 3 Pulur et al 2009 said this points to the need to search for other diseases in the presence of any unusual clinical manifestation For example further studies could be performed to see if a second disease is the explanation for a McArdle person with unusually severe symptoms 9 6 2 A second disease which is not a muscle disease may exacerbate the symptoms of McArdle disease 9 6 2 1 Bulimia and sickle cell anaemia can make McArdle symptoms worse It has been reported that the eating disorder bulimia may exacerbate the symptoms of McArdle disease Pillarisetti and Ahmed 2007 described a McArdle person who had both bulimia and sickle cell trait by sickle cell trait the authors meant that the person was a carrier for sickle cell anaemia The authors said that bulimia could cause electrolyte changes in the body like hypokalemia and hypophosphatemia which could make rhabdomyolysis more likely The authors also say that both sickle cell trait and bulimia are known to make people unaffected by McArdle s more likely to have rhabdomyolysis 9 6 2 2 Epileptic seizures can make McArdle symptoms worse An example of a second disease making McArdle symptoms worse was presented by Ford et al 1973 who describe a male McArdle person who also had epilepsy Epileptic seizures caused the muscles to cramp up spasm and produced rhabdomyolysis Salmon and Turner 1965 also reported a McArdle s boy aged 16 who was diagnosed with McArdle s after a grand mal epilepsy convulsion led to rhabdomyolysis 9 7 A second disease may make carriers of McArdle disease more likely to have symptoms of McArdle disease Carriers do not usually have symptoms of McArdle disease Quinlivan and Vissing 2007 and many other publications If a person is a carrier for two similar diseases which affect energy metabolism they may uncharacteristically have symptoms of one or both diseases Vockley et al 2000 described this as synergistic heterozygosity They reported one person who was a carrier for McArdle disease 29 of normal amount of muscle glycogen phosphorylase phosphorylase b kinase deficiency a subdivision of GSD VI 37 of normal and CPT II deficiency 50 of normal a carrier for Q12X mutation in AMPD1 This research suggests that a second disease may explain why symptoms are occasionally seen in carriers of McArdle disease Papadimitriou et al 1990 described a man who developed McArdle s symptoms at the age of 30 years His muscle weakness then increased as he got older At the age of 40 he had myoglobinuria twice after heavy muscle exercise but did not have cramps contractures When he performed a forearm ischaemic test a rise in lactate was seen which suggested a diagnosis of It is not McArdle s However he had increased creatine kinase levels his CK level was 1040 IU when the normal in this case would have been 20 93 IU It was found that he was a carrier of McArdle disease and had 25 functional glycogen phosphorylase Possible explanations for why this man did develop symptoms of McArdle s could be because he had had a very physical lifestyle as a younger man including time in the army Alternatively it may be that he had a second Page 116 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

undiagnosed muscle disease which led to muscle degeneration as he got older and triggered McArdle symptoms The authors did not say if they had tried to rule out other similar diseases Recommend reading Muscle pain in myophosphorylase deficiency McArdle disease The role of gender genotype and pain related coping by Oliver Romme Rudolf A Kley Gabriele Dekomien J rg T Epplen Matthias Vorgerd and Monika Hasenbring The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 117

Page 118 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

10 Mental and emotional aspects of McArdle disease There is no published information on the psychological effect of McArdle s McArdle s children may find that their parents and teachers don t believe that exercise can cause them to feel muscle pain Adults may be told by family doctors that they are imagining the symptoms are malingerers or that symptoms are due to being overweight Many McArdle people spend many years visiting family doctors and specialists before obtaining a correct diagnosis For many people receiving a diagnosis of McArdle disease is positive because it proves that the symptoms are caused by a known disease and enables them to begin to find out more about advice and treatments for McArdle disease However some people may feel depressed about having a condition which will affect them for life There are many ways to deal with these emotions including talking to friends family members or the family doctor The way in which McArdle people perceive their McArdle s symptoms can have an effect upon how difficult they find it to cope with symptoms on a day to day basis However symptoms are not necessarily just emotional One study suggested some McArdle people may suffer from symptoms similar to chronic fatigue There is also a small amount of evidence that McArdle people may perform less well than people unaffected by McArdle s at some tests of how well the brain can perform There is only a very limited amount of research into these factors and much more is needed Since McArdle people don t use a wheelchair or walking stick they may occasionally have to deal with negative comments from members of the public who don t understand why they need to park in a disabled space or walk slowly Even with friends and family many McArdle s adults use coping mechanisms to allow themselves to rest without other people noticing These techniques could include frequently pretending to tie up their shoelace stopping to look in shop windows or pretending to use a mobile phone Many McArdle people gain benefit from visiting a specialist who is knowledgeable about McArdle disease and can provide up to date information of the latest theories and treatments McArdle people may find it helpful to meet each other at the annual AGSD UK conferences There are several online chat groups which allow The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 119

McArdle people to meet other people with McArdle s which is especially valuable as the disease is rare However it is important to consult a McArdle specialist or your family doctor before following any recommendations or suggestions made on online chat groups Page 120 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

10 1 Many McArdle people have symptoms which are like chronic fatigue syndrome Almost half 40 18 of 45 of the McArdle people attending the UK McArdle Clinic r eported chronic fatigue like symptoms Quinlivan et al 2010 Quinlivan et al 2007 suggest that the fact that it often takes McArdle people many years to get a diagnosis could be a reason why many people have symptoms of chronic fatigue depression and anxiety It is an understandable reaction to many years of wondering What is wrong with me Chronic fatigue syndrome CFS causes long term tiredness fatigue that affects everyday life It does not go away with sleep or rest CFS is also known as ME which stands for myalgic encephalomyelitis Myalgia means muscle pain and encephalomyelitis means inflammation of the brain and spinal cord The causes of chronic fatigue like symptoms in McArdle people may not be the same as in people unaffected by McArdle s and some treatments may therefore not be suitable One treatment called pacing is a way to even out how much activity a person does each day This avoids having alternating good and bad days a good day where the person feels good and does a lot of activity but is then so tired that the next day is a bad day where they have to spend the whole day resting Pacing is a technique to reduce the amount of activity done on a good day so that they are less tired the next day and therefore avoid having a bad day It may be the case that for McArdle people who do have chronic fatigue like symptoms treatments such as pacing may help them cope with those symptoms better and improve their overall quality of life It is important to remember that the causes of chronic fatigue like symptoms in McArdle people may not be the same as in people unaffected by McArdle s and that some treatments may therefore not be suitable There is no published research that any treatments for chronic fatigue have been tried on McArdle people 10 2 Lack of muscle glycogen phosphorylase may affect brain function of McArdle people Edelstyn and Quinlivan 2007 described a pilot study of neuropsychological performance brain function in people with McArdle disease Ten McArdle people were compared to ten unaffected people and were found to perform significantly worse on tests of verbal fluency and verbal memory and less well than unaffected people in some other cognitive tests This suggests that the lack of muscle glycogen phosphorylase may also be detrimental to brain function in McArdle people There are several possible explanations for this In people unaffected by McArdle disease the brain has been shown to contain muscle glycogen phosphorylase brain glycogen phosphorylase and a dimer pair made of the brain and the muscle form In unaffected human brain muscle glycogen phosphorylase was found to provide 25 of the total amount of functional glycogen phosphorylase Bresolin et al 1983 In McArdle people muscle glycogen phosphorylase is absent in the brain so this may reduce the total amount of glycogen phosphorylase in the brain The brain consumes about 60 of the glucose used by the whole body when resting Berg et al 2008 The lack of functional muscle glycogen phosphorylase may affect brain function in McArdle people directly by reducing the amount of glucose available to the brain 80 of the vitamin B6 in the body is associated with muscle glycogen phosphorylase Beynon et al 1995 Pyridoxal 5 phosphate PLP is the metabolically active form of vitamin B6 Many reactions The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 121

in amino acid metabolism require the presence of PLP such as decarboxylases which are required in the synthesis of neurotransmitters An adequate PLP supply in brain tissue is therefore essential for normal brain function Williams 2003 If muscle glycogen phosphorylase is absent this may decrease the amount of PLP available both in the brain and throughout the body Beynon et al 1995 It has been shown that muscle and brain glycogen phosphorylase can bind together reviewed in Wright 2009 If a small number of McArdle people have muscle glycogen phosphorylase which is present but not functional this non functional muscle glycogen phosphorylase could bind to brain glycogen phosphorylase stopping it from functioning An excessive accumulation of glycogen in the brain may be detrimental Edelstyn and Quinlivan 2007 mention a report of a McArdle person with abnormal deposition of glycogen detected by brain MRS They also suggest that the abnormal rise in ammonia that occurs throughout the body in McArdle people during exercise may cause abnormal psychological function It should be noted that there has only been one study of psychological function to date by Edelstyn and Quinlivan and further studies are needed to confirm the results 10 3 Psychological issues There is no published information on the psychological effect of McArdle s Anecdotally McArdle people report childhood trauma everyday embarrassment depression fear and in some cases possibly even hysteria or a hyper awareness hypochondria These experiences are likely to be similar to those experienced by other people with rare diseases Except where a reference is given the information in this section is anecdotal 10 3 1 Before diagnosis 10 3 1 1 Psychology of being an undiagnosed McArdle s Most McArdle people were not diagnosed until adulthood and therefore spent their childhood struggling to run and exercise but unsure that there was a definite problem such as McArdle s Some McArdle s children found that their parents did not believe them when they said that exercise caused them pain They may have suffered from teasing or bullying because they were unable to run around in play or during exercise and sports classes at school 10 3 1 2 A rapid diagnosis in childhood is ideal A person who gets a rapid diagnosis ideally in childhood is probably likely to have fewer psychological problems An early diagnosis should allow the child to grow up following current recommendations such as frequent moderate exercise but avoiding intense exercise which is likely to lead to muscle damage An early diagnosis would allow the parents to inform physical education gym teachers to ensure that the McArdle s child is not pushed to exercise beyond their limits An early diagnosis would allow the child to inform friends and family of their limitations and hopefully feel unembarrassed about stopping and resting when necessary Page 122 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

10 3 1 3 Psychology of being an undiagnosed McArdle s adult A McArdle s adult who has not yet been correctly diagnosed may find that their family doctor doesn t believe that the symptoms are real and dismisses them as a hypochondriac or malingerer A McArdle s adult may also find that family and friends also don t believe that the symptoms are real They may find this very depressing and frustrating as they know that there is something wrong but it has not been correctly diagnosed Family and friends may not be very sympathetic since they have no proof that anything is wrong An undiagnosed McArdle s adult may feel angry that family friends family doctor doesn t believe that they have a problem Prior to being diagnosed McArdle people may feel isolated because no one else has similar symptoms 10 3 2 Trying to get a diagnosis 10 3 2 1 It can take a long time for McArdle people to get a correct diagnosis Many McArdle people spend many years seeking diagnosis before obtaining a correct diagnosis They often have to see many different family doctors and specialists Based upon a study of 45 McArdle patients visiting the UK McArdle Clinic Quinlivan et al 2010 reported that 84 had McArdle symptoms from the age of 10 years old or younger but about half 49 were not diagnosed until they were more than 30 years old This suggests that it can take around 10 20 years for McArdle people to receive a correct diagnosis Many McArdle people have been misdiagnosed and some will have received treatments for this incorrect diagnosis Some examples of these diseases are given in section 2 5 1 10 3 2 2 Many family doctors may incorrectly imagine that a McArdle person is a hypochondriac malingerer or that symptoms are due to being overweight McArdle s is a real condition with a physical cause the lack of muscle glycogen phosphorylase Much is known about the cause of McArdle s the way in which it affects the body and current treatments these are subjects covered in this Handbook However family doctors who have not heard of McArdle disease may dismiss a person with McArdle s as having hypochondria or being a malingerer Hypochondria is a mental disorder where people believe that they have a medical illness even though family doctors are unable to find anything wrong In some cases the physical symptoms can be caused by the person thinking that they have the illness People with hyperchondria may visit the family doctor frequently and may have a high level of worry about their symptoms People with hypochondria genuinely believe that they have an illness even though family doctors are unable to find anything wrong It is possible to understand how a family doctor can incorrectly imagine that a McArdle person who comes to see them frequently saying that something is wrong but who is able to walk around and appears to be physically well could have hypochondria A person who is a malingerer knows that they do not have an illness but pretends to have symptoms in order to avoid work or for financial reasons e g to get disability benefit or for another purpose such as getting sympathy from family members Many family doctors have not heard of McArdle s and don t recognise the symptoms Many McArdle people are overweight discussed in more details in section 4 2 3 and it is understandable that when a family doctor is presented with a patient who is overweight struggles to exercise and has muscle pains then the family doctor may incorrectly imagine these symptoms are all caused by the person being overweight and recommend more exercise The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 123

10 3 3 After diagnosis 10 3 3 1 Receiving a diagnosis of McArdle s Many people will feel relief at finally getting a diagnosis of McArdle s especially if it has taken a long time to obtain that diagnosis McArdle people may feel vindicated because a diagnosis will prove to family friends your family doctor that the problem is real not imagined A diagnosis allows you to begin reading about McArdle s online and elsewhere and to find out more about treatments It also allows you to make contact with other McArdle people via chat groups or e mail groups who can provide support 10 3 3 2 Coping with a diagnosis of a chronic illness Although many McArdle people will feel relief at having finally got a diagnosis diagnosis of a chronic illness may also pose challenges The information which follows is not specific to McArdle disease but is general information about how to cope with a diagnosis of a chronic illness de Ridder et al 2008 define chronic illnesses as disorders that persist for an extended period and affect a person s ability to function normally Interestingly de Ridder et al say that it is estimated that half the population 50 of people have a chronic physical condition which requires medical treatment Examples of chronic illnesses include diabetes which can be controlled with medication or rheumatoid arthritis which can cause physical disability and pain Chronic illnesses can change the person s life is many ways for example by limiting the amount of activity they can do Quinlivan et al 2010 found that 31 14 of 45 of McArdle people had been treated at some time for anxiety and or depression and Rommel et al 2006 reported that 29 7 of 24 of McArdle people had experienced mild depression de Ridder et al 2008 note that people with chronic illness typically have anxiety depression and other negative emotions Emotional reactions to chronic illness can basically be divided into two groups one is avoidance and suppression of emotions and the other is expression and acknowledgement of emotions Despite the common belief that it is better to express emotions the authors note that this is only the case in more expressive cultures such as North American and Western European cultures The authors note that non expression of emotions is better for people who live in less emotionally expressive cultures such as some Asian cultures de Ridder et al reviewed many studies and found that emotional expression led to improvements in the amount of physical activity people could do mobility and in the number of symptoms reported and even produced positive changes in the body which could be measured by laboratory tests suggesting it was a physical improvement not just a change in the person s perception of the situation It may be that discussing the emotions and feelings associated with being diagnosed with a chronic illness may help people to feel more comfortable with the diagnosis People who do not discuss their feelings and bottle them up may feel more stressed Stress is known to have negative effects upon health Another benefit of discussing feelings and emotions may be that it leads to feelings of closeness with either the friend relative or health professional who you talk to The challenge is how to learn to adapt life to work around McArdle s de Ridder et al note that many people with chronic diseases also have an increase of some cytokines the cytokine IL 6 is discussed further in section 9 2 It has been shown that some cytokines can produce feelings of fatigue irritability demoralisation and may cause feelings of depression In this case the cytokines are producing real changes in the feelings and emotions Drugs which block the effect of these Page 124 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

cytokines have been tested in people with rheumatoid arthritis and have helped to improve the way those people felt At present it is not known if cytokines in McArdle people may have this effect or whether drug treatments would help Humans have a natural response to illness which is to rest as this conserves energy and promotes healing de Ridder et al 2008 However this response is not always of use to the person and is in contrast to the moderate exercise now recommended for McArdle people see section 4 2 Some people diagnosed with chronic illness find it hard to follow a new diet exercise or other advice This is most likely if people feel that a large amount of time and effort is needed to follow this advice and or it may not produce much benefit Some people may suffer from major depression whereas other people may have guilt or anxiety about not following the ideal diet or the ideal exercise programme or worry about the negative effects of the disease such as worries about muscle wasting in older age The authors also noted that having a positive mood can help people manage their condition better and improve wellbeing de Ridder et al 2008 describe a person who has successfully adjusted to a chronic illness as having successfully adapted to the new situation learning to work around the disability staying emotionally balanced and maintaining healthy relationships with friends and family Not suffering from psychological disorders not letting the disability have a negative effect on their life and being able to do tasks such as a job which they want to do A person who has successfully adjusted to a chronic illness will be able to feel satisfied and happy with their life 10 3 3 3 Psychology of how other people perceive a McArdle s adult There are several issues which have been mentioned to me by McArdle s adults One problem is that you look completely normal Since McArdle s does not mean that you have to use a wheelchair or a walking stick the general population may not realise that you struggle to walk long distances Some McArdle people may feel embarrassed if they need to stop and rest during exercise for example during an exercise class or while out for a walk with friends Unless the class teacher or your friends knows about McArdle s it can be embarrassing to be the one person who needs to stop and rest In particular I would imagine that it is hardest being a young person or a young man as these would be perceived by others as being fit and able to exercise easily Some McArdle s adults who use disabled parking spaces or lifts rather than stairs have been accused of using them inappropriately by other people McArdle people may also feel annoyed depressed frustrated that friends family and work colleagues may have to help you out Many McArdle s adults use coping mechanisms to allow themselves to rest without other people noticing These techniques could include frequently pretending to tie up their shoelace stopping to look in shop windows or pretending to use a mobile phone 10 3 4 Positive steps to dealing with these issues Many McArdle people find that visiting a specialist such as Dr Quinlivan at the UK McArdle clinic can have a huge benefit Unlike a family doctor who may never have met a person with McArdle s before a specialist will have met many people with McArdle s The specialist will understand McArdle s much better and will know what is normal or unusual for people with McArdle s They are also likely to be involved in research and clinical trials and will keep up to date on the latest theories and treatments The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 125

Many McArdle people gain huge benefit from being in contact with other people with McArdle s E mail chat groups such as GSDnet and web based chat groups such the McArdle Disease Facebook group allow people with McArdle s to compare notes and share hints and tips There can be differences in the advice given by McArdle s specialists and this can be a way for McArdle people to tell each other about this advice This is also a good way to find out if and when new treatment ideas are developed 10 3 5 Websites and internet resources for people interested in McArdle disease Several website and an e mail chat group are listed below which offer the opportunity to chat online with other McArdle people Table 10 1 However it is important to remember that many of the people expressing views and opinions on these sites are not expert It is also possible that some of them have a different disease and have been misdiagnosed with McArdle s or not received a proper diagnosis It is therefore important to consult a McArdle specialist or your family doctor before following any recommendations or suggestions made on online chat groups Organisation AGSD UK AGSD USA Facebook Muscular Dyst Campaign MD Personal webs NORD Rare dis community GSDnet Pubmed Google schola Google books Table 10 1 Usefu Page 126 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

ul websites for McArdle people No responsibility is taken for the accuracy of the information provided on these websites http www ncbi nlm nih gov pubmed Google resource Search engine for medical and scientific publications Can be searched using paper title author and date http scholar google co uk schhp hl e Google resource Search engine for published books Can be searched using book title author and date or topic For some books a whole or partial online freeview is available http books google co uk bkshp hl en The McArdle Disease Handbook Version 1 1 1 Charity site Web site and patient chat group sease Patient chat group although this is not used much by McArdle people Kathryn Birch http www facebook com group php g http www muscular dystrophy org http mcardlesdisease org http www inspire com groups rare disease discussion glycogen storage dis disease http www agsd org uk Communicatio 1017 Default aspx Google resource Search engine for published books Can be searched using book title author and date or topic For some books a whole or partial online freeview is available Google resource Search engine for medical and scientific publications Can be searched using paper title author and date Scientific resource Search engine for medical and scientific publications Can be searched using paper title author and date E mail chat group for people with glycogen storage diseases including McArdle s http www agsd org uk http books google co uk bkshp hl en tab sp http scholar google co uk schhp hl en tab ws http www ncbi nlm nih gov pubmed http www agsd org uk Communications GSDNet tabid 1017 Default aspx http www inspire com groups rare disease discussion glycogen storage disease v mcardles disease http mcardlesdisease org http www muscular dystrophy org http www facebook com group php gid 2646925066 http www agsdus org Website address http www agsdus org Page 127 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 127 Table 10 1 Useful websites for McArdle people No responsibility is taken for the accuracy of the information provided on these websites Google books trophy DC Patient chat group although this is not used much by McArdle people Charity Google scholar Pubmed GSDnet E mail chat group for people with glycogen storage diseases including McArdle s Web site and patient chat group Patient chat group NORD Rare disease community Personal website Charity Patient chat group Charity http www agsd org uk Type of organisation Muscular Dystrophy Campaign MDC Facebook Scientific resource Search engine for medical and scientific publications Can be searched using paper title author and date Charity Website address Charity AGSD USA AGSD UK Type of organisation ar Organisation

Online resources There is further information on chronic fatigue and ME on the following website It is important to remember that the causes of chronic fatigue like symptoms in McArdle people may not be the same as in people unaffected by McArdle s and that some treatments may therefore not be suitable http www nhs uk me introduction asp Page 128 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

11 The effect of McArdle s on sexual activity pregnancy and birth Sexual activity usually involves movement and exercise Very few publications mention this topic but it has been reported that sexual activity can lead to muscle cramps for McArdle men and women There is very little published advice but one suggestion is to have a sugary drink prior to planned exercise such as sexual activity The most relevant expert for these issues would be a sexual therapist with an interest in helping people who have limited mobility McArdle s women anecdotally report a worsening of symptoms a week or two before menstruation having a period There have not been any studies to verify this suggestion or to provide any explanations for this There is no published information on whether McArdle disease has any effect upon fertility but it seems likely that McArdle disease does not affect the fertility of men or women with McArdle s so appropriate contraception should be used if pregnancy is not desired McArdle disease does not appear to increase the risk of complications for women during pregnancy or for giving birth Most McArdle women are able to have a vaginal birth A small number of McArdle women have caesarean delivery but this is similar to the numbers of women unaffected by McArdle s who have caesarean delivery Anecdotally some McArdle s women say that they have fewer McArdle s symptoms when they are pregnant but there is no published data to confirm this At present no tests are available to screen an unborn or newborn child to diagnose whether they will have McArdle disease A genetic counsellor can provide you with information about the chances of a child inheriting McArdle disease The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 129

11 1 Sexual activity Sexual activity usually involves exercise this may be static using your muscles to hold yourself in one position for a long time like yoga or repetitive movements for a long time or fast movements It is obvious that McArdle s is likely to have an effect upon the ability of McArdle people to do these activities Unfortunately there is hardly any published information on the effect of McArdle disease on sexual activity and intimate relationships Hockaday et al 1964 reported the case of a 51 year old McArdle man who found that symptoms of muscle pain in the legs were worse if he had had sexual intercourse the previous night Quinlivan et al 2010 said that McArdle men and McArdle women reported muscle cramps with or without myoglobinuria occurring as a consequence of sexual intercourse The lack of published information is likely to be due to several reasons because it can be hard to quantify because McArdle people may be embarrassed to mention it to their family doctors and because the doctors who diagnose and treat McArdle people tend to be neurologists and muscle specialists and therefore do not have any expertise and possibly no interest in sexual issues The most relevant expert for these issues would be a sexual therapist with an interest in helping people who have limited mobility In the absence of any published advice here are some approaches I would suggest Find and apply advice for people who have limited mobility for example advice for people who have arthritis bearing in mind what you know about McArdle disease and avoiding movements or positions which cause pain or are likely to lead to muscle damage or contracture Use the latest advice regarding exercise Warm up and get into a second wind if possible The only published piece of advice relating to McArdle disease and sexual intercourse which I have been able to find is a suggestion to have a sugary drink just prior to sexual intercourse This having a sucrose drink might be a useful therapy prior to planned vigorous exercise such as sexual intercourse Quinlivan and Vissing 2007 Communication Be willing to communicate what you want what works what doesn t work what you enjoy or don t enjoy being prepared to stop or change positions if your muscles begin to hurt Consider using pillows or other accessories to reduce the need to use your muscles to hold you in a certain position 11 2 The menstrual cycle and its effect upon exercise and perception of pain for McArdle s women There is no published information on the effect of female hormones or the female menstrual cycle on McArdle s symptoms It has anecdotally been reported by women with McArdle s that they experience a worsening of McArdle s symptoms a week or two before menstruation having a period Possible explanations for this anecdotal observation could include The menstrual cycle could physically affect the ability of McArdle s women to exercise Page 130 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

The menstrual cycle could physically or mentally affect the perception of pain by McArdle s women The menstrual cycle could mentally affect how distressing women find McArdle s symptoms There is no information available on these topics regarding women with McArdle s but some research on similar topics on women unaffected by McArdle s is discussed below The menstrual cycle can be broken down into two parts the time between the start of menstrual bleeding the period and ovulation which is called the follicular phase and the time between ovulation and the start of menstrual bleeding called the luteal phase 11 2 1 Does the menstrual cycle affect the ability of women unaffected by McArdle s to exercise There have been many investigations into whether the menstrual cycle affects the ability of women to exercise In particular studies have focussed on the effect of menstrual cycle on the performance of female athletes According to Janse de Jonge 2003 current literature indicates that VO2max is not affected by the menstrual cycle see 6 4 4 1 for further discussion of VO2max which suggests that performance of female athletes is not affected by the menstrual cycle However the authors mention that some studies suggest that women unaffected by McArdle s may have higher cardiovascular strain during moderate exercise in the mid luteal phase They noted that women athletes are able to exercise for a shorter time before becoming exhausted during the mid luteal phase when body temperature is elevated This may mean that McArdle s women may find exercise slightly harder during the mid luteal phase especially in hot conditions 11 2 2 Studies on the perception of pain in women unaffected by McArdle s Riley et al 1999 reviewed 16 studies where women unaffected by McArdle s who were healthy and had no conditions which caused pain were tested to see whether their experience of pain varied at different times in their menstrual cycle They found that the women experienced least pain from pressure stimulation cold heat and ischemic muscle pain during the follicular phase than at other points in the menstrual cycle The authors of the review note that the research was not perfect as different stimuli were used to produce pain in different studies stimuli included pressure heat or cold Other problems with the research are that only small numbers of women were studied and the researchers may have struggled to define exactly which part of the menstrual cycle the women were in Pfleeger et al 1997 carried out a study with 11 women unaffected by McArdle s who performed an ischaemic forearm test The women were asked to say when the pain from their forearm became too great for them to continue exercising Their blood pressure and their pain levels from the forearm test were monitored at different times during the menstrual cycle and it was found that the level of pain experienced and the blood pressure were both highest during the luteal phase However it should be noted that Hoeger Bement 2009 found the opposite results that when women were asked to carry out a forearm test their perception of pain was not affected by which stage of the menstrual cycle they were in Clearly more research is required The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 131

11 2 3 The emotional changes associated with the menstrual cycle may make McArdle s women consider their symptoms to be worse at certain points It is possible that hormone changes during the menstrual cycle will affect how women perceive their symptoms Women who are unaffected by McArdle s often report emotional changes during their menstrual cycle The most dramatic of these occur just prior to the menstrual bleed period and are known as premenstrual syndrome or tension PMS PMT It has been suggested that all women experience some PMS symptoms which can vary from woman to woman Since symptoms of PMS include a depressed mood crying and tearfulness and anxiety my theory is a woman with PMS may perceive her McArdle s symptoms as being worse than usual although the difference may be in her frame of mind rather than the symptoms It has been reported that symptoms of chronic illnesses can be worse when women are experiencing PMS symptoms Examples of physical illnesses which are known to become worse for a woman when she is premenstrual include migrane Dzoljic et al 2002 epilepsy Hussain et al 2007 asthma Pereira Vega et al 2010 irritable bowel syndrome Houghton et al 2002 rheumatoid arthritis and diabetes Case and Reid 1998 There does not seem to be any information published about whether symptoms of muscle diseases become worse during the menstrual cycle which is probably because no research has been done into this topic 11 3 Fertility and contraception There is no published information on whether McArdle disease has any effect upon fertility but it seems likely that McArdle disease does not affect the fertility of men or women with McArdle s so appropriate contraception should be used if pregnancy is not desired Unfortunately the promising sounding paper Contraception and pregnancy in women affected by glycogen storage diseases Mairovitz et al 2002 is focussed on GSD I and the information is not relevant to McArdle s As discussed in section 14 2 2 it would be worthwhile discussing any medication or contraceptive method with your family doctor whilst also considering McArdle s For example you would want to discuss whether there could be any side effects such as an increased risk of rhabdomyolysis which might make some methods less suitable for a McArdle person 11 3 1 Prenatal testing for McArdle s and infant screening An absence of published reports suggests that prenatal testing is not currently available during pregnancy to determine whether an unborn baby will have McArdle disease Theoretically it would be possible to obtain a DNA sample from cells obtained by chorionic villus sampling or amniocentesis Milunky et al 2010 say that although testing for the mutations which cause McArdle s is theoretically possible there are no reports in the literature that they have been done Prenatal testing may not be currently available partly due to the rarity of McArdle s Also the development of prenatal tests tends to be prioritized for diseases which are fatal or highly debilitating As McArdle s symptoms are not as severe as many other muscle diseases for example Spinal muscular atrophy or Duchenne muscular dystrophy it may be a lower priority As McArdle s is recessive unless one or both parents have McArdle s there is often not a family history of McArdle s and therefore no clue that prenatal testing should could be considered Page 132 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Infant screening for McArdle s e g by a heel prick or blood test from a newborn baby is also not currently available It is likely to be for similar reasons as those given above because McArdle s is relatively rare not as severe as some other diseases and also because the advantage of having a diagnosis must be weighed against the cost of screening many newborns who would not have McArdle s Information about the chances of passing on McArdle s to your children should be discussed with a genetic counselor but a scientific explanation of the inheritance of McArdle s is given in section 3 11 4 Pregnancy and birth McArdle disease does not appear to increase the risk of complications for McArdle women during pregnancy or for giving birth Quinlivan et al 2010 11 4 1 Some McArdle s women report having fewer McArdle s symptoms during pregnancy Anecdotally some McArdle s women say that they have fewer McArdle s symptoms when they are pregnant There is no published data to confirm these anecdotal observations or to explain them Possible explanations for these anecdotal observations include Could a foetus unborn baby supply a McArdle s mother with the enzyme she is lacking Do the pregnancy hormones increase the level of glucose in the bloodstream of the McArdle s mother reducing symptoms Both these possibilities are discussed below 11 4 1 1 Could a foetus unborn baby supply a McArdle s mother with the enzyme she is lacking The explanation for this theory is that in the foetus the whole body is provided with energy by foetal glycogen phosphorylase this has the alternative name of brain glycogen phosphorylase The theory is that some of the foetal glycogen phosphorylase may be carried from the foetus in the bloodstream and transferred across the placenta into the mother s blood It would then be carried to the mother s muscles and be taken into the muscle cells It could then function in the muscle cells to replace the missing muscle glycogen phosphorylase so that the mother will no longer have symptoms of McArdle s I do not agree with this theory It seems unlikely that the foetal glycogen phosphorylase could get out of the foetus into the blood and then into the skeletal muscles If this was the case it would be a form of enzyme replacement therapy However as described in section 16 3 2 enzyme replacement therapy is not a suitable treatment for McArdle s as the enzyme is taken up into the lysosome the wrong location not the cytoplasm the location where glycogen phosphorylase is needed In an McArdle adult who is not pregnant the brain isoform does not leak out of the heart or smooth muscle such as the smooth muscle of the digestive tract and into skeletal muscle and cure McArdle s This suggests that the foetal enzyme probably can t leak out of the foetus and into the skeletal muscle The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 133

Walker 2006 carried out research into sheep and lambs with McArdle s or unaffected by McArdle s The gestation of a lamb is approximately 150 days Research by Walker suggests that foetal glycogen phosphorylase can be detected in a sheep foetus from the age of 40 days after conception the earliest time period tested by Walker and that foetal glycogen phosphorylase is the main isoform until 50 days after conception when muscle glycogen phosphorylase begins to take over and become the main isoform in sheep muscles It is likely that a similar situation occurs in humans 11 4 1 2 Do the pregnancy hormones increase the level of glucose in the bloodstream of the McArdle s mother reducing symptoms I suggest an alternative theory that being pregnant raises the level of glucose in the blood causing hyperglycemia which would produce a similar effect to drinking a sugary drink and would help pregnant McArdle s women exercise more easily with fewer McArdle s symptoms The foetus requires a high level of glucose for growth and development During pregnancy from about 6 weeks gestation the placenta produces a hormone called human placental lactogen HPL also known as human chorionic somatomammotropin HPL is released from the placenta into the mother s bloodstream HPL has an anti insulin effect which results in an increased amount of both glucose and fatty acids in the bloodstream in order to supply enough nutrients and energy to the foetus The amount of HPL secreted by the placenta increases as the foetus grows bigger HPL can also increase the amount of fatty acids in the bloodstream My unproven theory is that the increased levels of glucose and fatty acids in the blood would provide an improved energy source for the muscles reducing McArdle s symptoms for a pregnant McArdle woman HPL also has a small effect on increasing the production of tissues including muscle in a similar but weaker way to growth hormone The increase in glucose during pregnancy in women unaffected by McArdle s is well known If the levels of glucose in the blood are too high possibly due to the effect of HPL gestational diabetes may occur in pregnant women unaffected by McArdle s Gestational diabetes can occur very early in pregnancy and can last throughout pregnancy Gestational diabetes usually stops following birth If a phenomenon similar to gestational diabetes is occurring in pregnant McArdle s women this could explain why they return to a normal level of symptoms following birth which has been reported anecdotally by McArdle s women 11 4 2 Method of giving birth vaginal birth or caesarean delivery McArdle s does not appear to have any effect upon the ability of McArdle s women to have a natural birth and does not increase the need for a caesarean delivery There are a limited number of reports about McArdle s women giving birth but those which are available report both vaginal and caesarean births Quinlivan et al 2007 2010 carried out a review of the McArdle women who had attended the UK McArdle Clinic They described 14 McArdle s women who had had 21 pregnancies between them all pregnancies were uncomplicated although one lady had mild myoglobinuria 24 hours after delivery The authors found that 15 of these cases about 3 of 25 pregnancies had required intervention or caesarean which was not dissimilar from the 15 national average in the UK This is very limited data but it suggests that having McArdle s does not make women more likely to require a caesarean Page 134 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

The uterus womb is made of smooth muscle Smooth muscle has a different isoform of glycogen phosphorylase and is therefore not affected in McArdle s For this reason McArdle s women should not have a problem having a vaginal birth During vaginal birth your family doctors may choose to give you sucrose by an intravenous drip to provide an energy source to the muscles Cochrane and Alderman 1973 reported a case of a 21 year old McArdle woman She had a normal pregnancy She had a relatively normal vaginal delivery The second stage pushing stage was quite slow as she had been given an epidural anaesthetic which is known to slow down delivery in women unaffected by McArdle s Labour began spontaneously but was quite slow not unusual in a first birth She received dextrose a form of simple sugar and oxytocin chemical which stimulates contractions of the uterus intravenously The baby was healthy Both mother and child made normal progress after delivery The authors reported that contractions of the uterus were normal further suggesting that it is smooth muscle with another isoform of glycogen phosphorylase During pregnancy in case a planned or emergency caesarean is required you should remind your family doctor that McArdle people are at increased risk of malignant hyperthermia see section 12 3 Anecdotally some McArdle s women have reported that their arms were tired after giving birth so that they found it harder to hold the baby immediately afterwards Online resources There is further information on premenstrual syndrome on the NHS website http www nhs uk Conditions Premenstrual syndrome Pages Introduction aspx The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 135

Page 136 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

12 Medicines activities and other things which may be a greater risk for McArdle people Some drugs are known to have a potential side effect of rhabdomyolysis breakdown of muscle cells in people unaffected by McArdle s and these drugs may be more likely to cause rhabdomyolysis in McArdle people For example statins are a lipid lowering drug which is known to have a high risk of rhabdomyolysis in McArdle people It is best to avoid taking drugs which could cause rhabdomyolysis but if your family doctor feels that it is essential to prescribe the drug they may arrange to regularly monitor you to check for rhabdomyolysis Rhabdomyolysis can be detected by checking the levels of creatine kinase CK in the blood ideally by measuring your CK levels before taking the drug and then checking CK levels whilst being treated by the drug If the CK level becomes raised it could suggest that muscle damage is occurring McArdle people should beware of using painkillers for muscle pain Muscle pain has a protective effect to warn you not to exercise a damaged muscle Painkillers could mask this warning so that you continue to exercise resulting in further damage to the muscle The phrase No pain no gain does not apply to McArdle people During surgery McArdle people are at increased risk of a complication similar to malignant hyperthermia caused by certain anaesthetics It is important to make sure that the surgeon and anaesthetist are aware of this risk so that they can monitor you closely during surgery McArdle people are also at risk of a rare condition called compartment syndrome This can be caused if a tourniquet or cuff is used which can lead to a build up of fluid in the muscle with potential to cause muscle damage Shivering from the cold and getting angry or scared could cause a McArdle person to tense their muscles which could lead to muscle pain and damage Swimming is a potentially dangerous activity for McArdle people because if the muscles run out of energy you may not be able to tread water or swim to safety The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 137

12 1 Medicines There are some drugs which have an increased risk of causing rhabdomyolysis as a side effect in people unaffected by McArdle s and are summarised in table Table 12 1 These drugs are more likely to cause rhabdomyolysis in McArdle people Some of these drugs have been reported to cause rhabdomyolysis in McArdle people and this is discussed in more detail below Rhabdomyolysis is discussed further in section 5 If your family doctor suggests that you take one of the drugs listed in Table 12 1 I would recommend that you discuss with them whether McArdle s puts you at increased risk of rhabdomyolysis during the treatment Your family doctor may still decide to prescribe the drug but may regularly monitor you See section 14 2 for more information on helping your family doctor to treat you 12 1 1 Lipid lowering drugs such as statins may exacerbate rhabdomyolysis in McArdle people Some people unaffected by McArdle s had side effects including rhabdomyolysis when treated with lipid lowering drugs such as statins Vladutiu et al 2006 When these people were tested and compared to people receiving the therapy with no symptoms of muscle damage and also to people who had not been treated with statins it was found that 10 of the 110 people with side effects were heterozygous or homozygous for mutations causing carnitine palmitoyltransferase II CPT II deficiency which affects fatty acid metabolism McArdle disease or myoadenylate deaminase deficiency MADD involved in energy metabolism in muscle cells The effect of the statins upon energy metabolism combined with a genetic disease affecting mitochondrial or fatty acid metabolism seemed to exacerbate muscle damage and rhabdomyolysis 12 1 2 When combined with a statin some drugs produce a much higher risk of rhabdomyolysis Combination of a statin with a fibrate or with nicotinic acid carries an increased risk of side effects such as rhabdomyolysis in people unaffected by McArdle s Also any drug which increases the concentration of a statin in the blood is likely to increase the risk of rhabdomyolysis BNF 2009 12 1 2 1 Fibrates Fibrates include bezafibrate ciprofibrate fenofibrate and gemfibrozil They act by decreasing the amount of triglycerides in the blood However a combination of a fibrate with a statin increases the risk of rhabdomyolysis in people unaffected by McArdle s The British National Formulary edition 58 states that gemfibrozil and statins should not be used at the same time 12 1 2 2 Nicotinic acid Nicotinic acid can be used to lower cholesterol and triglyceride concentrations by reducing the amounts of these compounds made by the body In people unaffected by McArdle s muscle pain and rhabdomyolysis have been reported as rare side effects Page 138 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

drugs used to treat infections caused Levofloxacin Daptomycin Ofloxacin Co Trimoxazole sthetics also see section 12 3 Suxamethonium Chloride Propofol nt drugs used to treat depression rheumatic diseases and gout relief gs which have a side effect of rhabdomyolysis in people unaffected by McArdle s information summarised from BNF 2009 Venlafaxine Adalimumab Morphine Salts The McArdle Disease Handbook Version 1 1 1 Entacapone Tolcapone Levodopa Ecstacy Also known as Methylenedioxymethamfetamine Mdma Morphine Salts Adalimumab Venlafaxine Suxamethonium Chloride Propofol Levofloxacin Daptomycin Ofloxacin Co Trimoxazole Dasatinib Ezetimibe Nicotinic Acid Fibrates Rosuvastatin Bezafibrate Gemfibrozil Stat Kathryn Birch Page 139 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 139 Table 12 1 Drugs which have a side effect of rhabdomyolysis in people unaffected by McArdle s information summarised from BNF 2009 Used for pain relief Used to treat rheumatic diseases and gout Aripiprazole Olanzapine Antidepressant drugs used to treat depression Zonisamide Pregabalin Aripiprazole Olanzapine Dasatinib Antibacterial drugs used to treat infections caused by bacteria General anaesthetics also see section 12 3 Antipsychotic drugs used to treat psychoses and other mental health problems Used to treat some kinds of cancer Lamivudine Tenofovir Disoproxil Raltegravir Protease Inhibitors Didanosine Ecstacy Also known as Methylenedioxymethamfetamine Mdma Zonisamide Pregabalin Lamivudine Tenofovir Disoproxil Raltegravir Protease Inhibitors Didanosine Entacapone Tolcapone Levodopa Ezetimibe Nicotinic Acid Fibrates Rosuvastatin Bezafibrate Gemfibrozil Statins ng used to reduce levels of cholesterol es in the blood Parkinson s disease Illegal stimulants drugs used to treat psychoses and health problems some kinds of cancer Antiepileptics used to treat epilepsy Antiviral drugs used to treat HIV infection Lipid regulating used to reduce levels of cholesterol or triglycerides in the blood Used to treat Parkinson s disease used to treat epilepsy Examples of the type of drug ants Type of drug s used to treat HIV infection Examples of the type of drug

12 1 3 Other drugs to reduce cholesterol may exacerbate rhabdomyolysis in McArdle people Perez Calvo 2005 reported a case of a McArdle man who was treated with ezetimibe Ezetimibe is a drug which inhibits absorption of cholesterol in the intestine The person was treated for many months The person had no ill effects for 20 weeks and then began to suffer from fatigue myoglobinuria and weakness His CK levels also rose The family doctors treating him decided to discontinue the treatment and the CK values went down to normal after 4 weeks It must be noted that this is a single case study and that this person also had several other medical problems including type 2 diabetes mellitus which could have affected the outcome Ezetimbe is used to treat primary hypercholesterolaemia high cholesterol levels Ezetimibe may be marketed alone as a drug called Ezetrol or Zetia Simvastatin is a kind of statin Ezetimibe combined with simvastatin Zocor is marketed as Inegy BNF 2009 or Vytorin 12 2 Pain relieving mediation Anecdotal advice is that drugs for muscle pain should not be used routinely The principle reason for this is because if muscle damage is causing the pain then the pain will warn the person not to exercise which could cause further muscle damage In this way the pain has a positive effect to protect the muscles from being damaged further Pain relieving medication would remove this pain and could lead to the muscle being used and damaged further Some forms of pain relief may also have an increased risk of rhabdomyolysis see Table 12 1 It is important to note that the adage No pain no gain does not apply to McArdle people 12 3 McArdle people are at increased risks of particular complications during surgery 12 3 1 Lack of muscle glycogen phosphorylase may put McArdle people at increased risk of malignant hyperthermia like symptoms caused by anaesthetics Malignant hyperthermia is a life threatening condition which is triggered by certain anaesthetics one example of which is muscle relaxant suxamethonium chloride These drugs can cause a major increase in skeletal muscle oxidative metabolism whereby the muscle cells run out of oxygen and develop an excess of carbon dioxide The increase in metabolism can cause an abnormal rise in body temperature which is why the condition is described as hyperthermia Medical treatment to stop the temperature rise is essential as in the worst case scenario it would be possible for the body temperature to continue to rise until it leads to death Price Evans 1993 Malignant hyperthermia is an autosomal dominantly inherited disorder associated with central core disease Central core disease is caused by a mutation in the RYR1 gene which encodes ryanodine receptor 1 a channel for calcium ions in skeletal muscle required for muscle contractions the role of calcium in muscle contractions is discussed further in section 4 3 Central core disease causes a lack of functional muscle glycogen phosphorylase within the core of the muscle cell Isaacs et al 1975 Dubowitz et al 2007 although it is found in other regions of the muscle cell This may suggest that McArdle people who also don t have functional muscle glycogen phosphorylase could Page 140 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

be at risk of malignant hyperthermia caused by anaesthetics Cases of McArdle people being positive for malignant hyperthermia have been reported Isaacs et al 1989 reported one person and Aquaron et al 2007 described two families one with three affected siblings and one with two affected siblings One current test for susceptibility to malignant hyperthermia is an in vitro contracture test a muscle biopsy is bathed in a solution containing caffeine or halothane to see whether contracture occurs which is positive for many McArdle disease people Bollig et al 2005 If a person is susceptible malignant hyperthermia usually occurs within one hour of being given a general anaesthetic Rosenberg et al 2007 Dantrolene sodium can be used to prevent treat malignant hyperthermia Dantrolene sodium is discussed further in section 7 1 5 IMPORTANT Before having a general anaesthetic you should inform your surgeon anaesthetist that McArdle people are at an increased risk of malignant hyperthermia Ideally you would inform them in advance of the surgery and then remind them on the day of surgery This will allow the medical staff to decide carefully which anaesthetic to use and to ensure they monitor you carefully They may also decide to have dantrolene sodium available in case malignant hyperthermia does occur If a caesarean delivery is required for a pregnant McArdle woman the surgeon should be aware of the risk of malignant hyperthermia Bollig et al 2005 also recommend to surgeons that measures for preventing muscle ischaemia and rhabdomyolysis should be kept in mind as well as the potential for these patients with McArdle disease to develop postoperative fatigue myoglobinuria and renal failure 12 3 2 McArdle people may be at risk of a rare condition called Compartment syndrome caused by use of a tourniquet or cuff Compartment syndrome is also known as compartment pressure syndrome This is a rare complication caused by use of a tourniquet or cuff The compartment is a small area between the layers of the muscle Usually a very small amount of fluid is present in this space and is used for contraction and relaxation of the muscle There is no room for any additional fluid Compartment syndrome is a build up of fluid in the compartment Symptoms of compartment syndrome include severe muscle pain muscle weakness and very tense skin over the muscle It can reduce the ability of blood to pass through the muscle so that no pulse can be felt and the worst case scenario is paralysis There is a report of compartment syndrome in a person with Hers disease Niepel et al 2004 reported a person with Her s disease who was given an ischaemic forearm test Later that afternoon he had continuing pain in his forearm and inability to extend his fingers followed by reduced sensation in his hand Compartment syndrome was diagnosed and an emergency operation was performed Unfortunately his recovery was incomplete and he was left with some loss of sensation Although this case occurred in a person with Her s disease there is also a single reported case of compartment syndrome in a McArdle person who performed the ischaemic forearm test Lindner et al 2001 Anecdotally McArdle people have reported getting compartment syndrome following on from a fixed contracture A possible explanation is that the muscle contracture causes pressure on the muscle cells which causes damage and leads to compartment syndrome General recommendations for people unaffected by McArdle s are that a patient s own and family history information about previous cases of compartment syndrome should be obtained The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 141

Tourniquet time should be limited to less than 90 minutes and that the tourniquet should be released before encasing a muscle in a solid cast such as that used on a broken arm IMPORTANT Before having a surgery you should inform your surgeon anaesthetist that McArdle people are at an increased risk of compartment syndrome Ideally the surgeon would avoid use of a tourniquet or cuff although this would have to be balanced against the risk of not using it for example if a person might bleed to death If a tourniquet is still needed the surgeon should be informed about the possible risk of muscle damage with subsequent myoglobinuria Bollig et al 2005 Medical advice should be sought urgently if after carrying out an ischaemic forearm exercise test a loss of sensation is felt in the fingers continued pain is present and an inability to extend move the fingers 12 4 Some situations may make McArdle s symptoms worse 12 4 1 Cold temperature Rommel et al 2006 found that some McArdle people had increased pain caused by environmental factors such as a cold temperature 12 4 2 Getting angry Rommel et al 2006 found that some McArdle people had increased pain caused by factors such as a psychological distress Becoming very angry can cause a McArdle person to tense up their muscles I have heard an anecdotal case where a McArdle person became very angry so that their muscles all tensed up resulting in contractures and rhabdomyolysis It is possible that being very scared could produce a similar effect 12 4 3 Swimming Swimming is an activity which is potentially dangerous for McArdle people This is because if the muscles run out of energy whilst a McArdle person is swimming they will not be able to tread water or swim to safety This could result in the McArdle person drowning For this reason McArdle people should never swim in water in which they cannot stand up There is a published report of a 6 year old McArdle s child who almost drowned whilst swimming prior to being diagnosed with McArdle s Roubertie et al 1998 12 4 4 Treatment by anyone who moves the body e g physiotherapy osteopathy chiropractor massage If you require treatment by a person who moves the body treatment for muscle pain massage or bone related issues it is very important to ensure that the person understands McArdle s Anecdotally some McArdle people report that treatment by a physiotherapist can cause muscle pain and potentially muscle damage Page 142 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

13 McArdle disease may increase the chances of having some diseases and conditions McArdle people may be more likely to have some gout McArdle people may also be more likely to have symptoms similar to insulin resistance type 2 diabetes These symptoms may be caused by the accumulation of glycogen in the muscle cells of McArdle people and may not be exactly the same as type 2 diabetes McArdle s does not appear to cause heart problems or liver problems although compounds from damaged muscle cells may cause incorrect results in some tests for liver disease The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 143

13 1 McArdle s may increase the risk of gout Gout is a painful swelling of the joints which is caused by build up of uric acid crystals It can be caused by high concentrations of uric acid crystals in the blood Uric acid can be produced during the breakdown of purines in food during digestion It is also possible that the level of uric acid in the blood may increase following exercise although whether this is the case and what the mechanism could be is still unclear McCrudden 2008 There is some evidence that having McArdle s may increase the risk of having gout 11 5 out of 45 of the McArdle people attending the UK McArdle Clinic had received treatment for gout Quinlivan et al 2010 compared to approximately 3 of the general population Puig et al 1992 reported the case of a person with McArdle disease who also had gout They carried out investigations to measure the amount of purine in the blood and urine after the McArdle person had vigorously exercised but did not see an increase in the level of uric acid in the blood or urine They therefore concluded that in this patient the association of McArdle disease with gout is coincidental Jinnai et al 1993 reported the case of a 28 year old McArdle man who had continuous hyperuricemia raised levels of uric acid in the blood They found that when the McArdle man carried out aerobic exercise using a bicycle ergometer it led to an increase in uric acid Exercise seemed to make the muscles speed up the rate of purine degradation which increased the levels of uric acid In this case report the authors claimed that there was a relationship between exercise and increased uric acid in the bloodstream They described the condition as myogenic hyperuircemia myogenic means it is caused by muscle contractions and hyperuricemia means an increased level of uric acid in the blood Mineo et al 1995 said that myogenic hyperuricemia is seen in glycolyctic defects McArdle s is a glycolytic defect They say that myogenic hyperuricemia is caused by excessive degradation of muscle purine nucleotides presumably as an energy source as the cells are not able to make energy in the usual way the usual way would be glycogenolysis Mineo et al 1987 carried out a study where they examined the amounts of purine in the bloodstream after exercise They found that for a person with McArdle s and also two people with GSD III and one person with GSD VII exercising led to accelerated breakdown of purines in the muscle cells This resulted in increased levels of breakdown products ammonia inosine and hypoxanthine in the blood The authors noted that these breakdown products can be used by the body to produce uric acid leading to hyperuircemia 13 2 Brain functioning There is some evidence that McArdle people may struggle more with some aspects of psychological functioning than people unaffected by McArdle s This is discussed in more detail in section 10 2 13 3 Respiratory problems Respiratory problems appear to be unusual in McArdle people but there have been some cases reported Lucia et al 2008a reported some McArdle people who had respiratory problems but they were all women Differences in the severity of symptoms between men and women are discussed further in section 9 5 Paradas et al 2005 report a McArdle woman with shortness of breath also known as dyspnea This same woman had been previously reported in the paper Page 144 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

McArdle disease presenting as unexplained dyspnea in a young woman by Voduc et al 2004 Harris et al 1985 also reported an elderly McArdle woman with shortness of breath There are a few reports of a rare infant form of McArdle s which was fatal due to respiratory failure but there were only 3 cases published and I strongly suspect that they all had a second disease problem which caused the respiratory failure This rare infant form is discussed further in section 8 2 1 13 4 McArdle s may cause symptoms of insulin resistance similar to type 2 diabetes Insulin plays a key role in controlling the amount of glucose in the blood and in enabling muscle cells to absorb glucose from the bloodstream which can then be used to provide energy see section 6 2 Diabetes is the inability to control the level of glucose sugar in the blood There are two forms of diabetes type 1 and type 2 Information about these forms of diabetes in people unaffected by McArdle s is provided in Table 13 1 McArdle people have very high levels of glycogen stored in their muscle cells There are several published reports that high levels of stored glycogen reduce the ability of insulin to stimulate the cells to take glucose from the bloodstream into the muscle cells This is known as insulin resistance and is similar to type 2 diabetes also known as non insulin dependent diabetes mellitus There has not been much research into insulin resistance in McArdle people but it is an important topic Personally I wonder if future research will show that almost all McArdle people have some insulin resistance caused by the high amount of glycogen stored in their muscle cells so I have included the following information Many more studies will be needed to show if this is the case Yamauchi et al 1996 reported a 64 year old McArdle woman who had type 2 diabetes NIDDM Thus we suggested that high plasma glucose and insulin due to NIDDM may induce blood borne glucose uptake with exercise Maeda et al 2002 reported a case of a 29 year old McArdle woman who also had insulin resistance Pre administration of glucagon had no effect on serum lactate and pyruvate levels after ischemic forearm exercise test while serum glucose elevated The glucose clamp test confirmed insulin resistance Maeda et al noted that that there was no reduction in the number of insulin receptors Her weight was 78 4kg and BMI was 32 0 so the authors suggested that Her obesity might be a causative factor of insulin resistance I wonder if instead it may have been excess glycogen storage due to McArdle s which had caused insulin resistance Dorin et al 1996 reported a McArdle person with type 2 diabetes NIDDM They hypothesised that insulin resistance would reduce the ability of the muscles to take up glucose during exercise and suggested that adding insulin intravenously would improve this They found that when they artificially added insulin it increased the amount of glucose able to get to the muscles and increased the amount of work that the McArdle person was able to do The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 145

Older than 40 years of age Type II diabetes Non insulin dependent diabetes mellitus NIDDM Adult onset diabetes Ketosis resistant diabetes Stable diabetes Diabetes mellitus type 2 Type 2 No Yes Low or normal Normal Insulin receptors on cells Can be associated with Page 146 Kathryn Birch Obesity being very overweight Obesity being very overweight Viral infection Is insulin required as a treatment Age when this type of diabetes first begins Is insulin required as a treatment Viral infection Yes No Out of all with diab common i Normal Quite severe Rare 5 10 with diabe Low or normal Quite moderate Very comm of people diabetes The McArdle Disease Handbook Version 1 1 1 Quite moderate Quite severe Symptoms The McArdle Disease Handbook Version 1 1 1 Symptoms Kathryn Birch Insulin receptors on cells Page 146 Table 13 1 Information about diabetes in people unaffected by McArdle s information from McArdle et al 2006 Less than 20 years of age although occasionally older than 40 years of age Type I diabetes Insulin dependent diabetes mellitus IDDM Ketosis prone diabetes Brittle diabetes Diabetes mellitus type I Older than 40 years of age Can be associated with II diabetes nsulin dependent tes mellitus NIDDM onset diabetes is resistant diabetes e diabetes etes mellitus type 2 Age when this type of diabetes first begins Less than 20 years of age although occasionally older than 40 years of age Type 1 on about diabetes in people unaffected by McArdle s information from McArdle et al 2006 Also known as I diabetes n dependent diabetes tus IDDM is prone diabetes e diabetes etes mellitus type I Type of diabetes known as Very common 90 95 of people with diabetes Rare 5 10 of people with diabetes Out of all the people with diabetes how common is this form

Nielsen et al 2002a compared 6 McArdle people with 6 unaffected people They gave each person a glucose drink and investigated whether the body could use insulin to stimulate the muscle cells to take up the glucose They found that the McArdle people had much less insulin stimulated uptake of glucose than the unaffected people Mineo et al 1984 gave McArdle people glucagon prior to exercise This relieved patients with McArdle disease from muscular symptoms during exercise and enhanced exercise performance It is likely that glucagon acted upon the liver causing a release of glucose into the bloodstream This would have acted in a similar way to having a sugary glucose drink immediately prior to exercise which is known to help McArdle people exercise more easily section 7 1 6 3 The authors note that a similar improvement in the ability to exercise was seen after giving glucose or glucose plus insulin the insulin would probably have helped the muscle cells to take up the glucose Interestingly the authors did not see an improvement in the ability to exercise when McArdle people were given insulin alone without glucose There is no suggestion that McArdle s may be associated with type 1 diabetes IDDM Davies et al 1977 reported a McArdle person who had type 1 diabetes At present this appears to be the only published report of a McArdle person with type 1 diabetes In the absence of any evidence to suggest a link it is likely that a report of a person having both McArdle s and type 1 diabetes is likely to be a coincidence 13 4 1 A discussion of whether insulin resistance could be caused by McArdle disease It is not clear to me whether the insulin resistance observed in some McArdle people is exactly the same as type 2 diabetes NIDDM observed in people unaffected by McArdle s It is possible that there are important differences between the insulin resistance seen in people with McArdle s and those unaffected by McArdle s In McArdle people the cause of insulin resistance may be different to the cause in people unaffected by McArdle s Nielsen et al 2002a suggested that the high level of glycogen storage in the muscle cells of McArdle people might cause insulin resistance This is not the cause of insulin resistance in people unaffected by McArdle s My personal unproven theory is that most McArdle people have some level of insulin resistance caused by glycogen storage in their muscle cells 13 4 1 1 A high level of glycogen in the muscle cells of McArdle people may lead to insulin resistance Usually insulin can stimulate muscle cells to take glucose from the bloodstream into the muscle cells This functions as a way of keeping the amount of glucose in the bloodstream constant It also helps to increase the amount of glucose in the muscle cells Derave et al 2000 found that a very high amount of glycogen in muscle cells led to the GLUT 4 proteins not responding to insulin this is called insulin resistance Nielsen et al 2002a compared McArdle people with unaffected people They gave each person a glucose drink and investigated whether the body could use insulin to stimulate the muscle cells to take up the glucose They found that the McArdle people had much less insulin stimulated use of glucose than the unaffected people The authors concluded that the high level of glycogen in the skeletal muscle cells caused McArdle people to be insulin resistant in terms of glucose uptake and stated that insulin action is decreased by high muscle glycogen content in skeletal muscle In addition the ability of insulin to decrease and increase the use of fat and carbohydrate to produce energy was also reduced in people with McArdle disease The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 147

13 4 1 2 High levels of some cytokines such as TNF and IL 6 in the bloodstream of McArdle people could lead to insulin resistance There is some evidence that McArdle people have raised levels of two cytokines small proteins called TNF and IL 6 Lucia et al 2008b These are both discussed further in section 9 2 It has been found that people with type 2 diabetes unaffected by McArdle s have high levels of TNF TNF is known to decrease the ability of insulin to stimulate muscle cells to take up glucose in rats by inhibiting the action of GLUT 4 and inhibit insulin receptor activity A possible explanation for the insulin resistance seen in McArdle people could be that the high levels of TNF and possibly IL 6 may reduce the ability of insulin to stimulate uptake of glucose from the bloodstream by GLUT 4 TNF and possibly IL 6 could therefore lead to insulin resistance This is an unproven theory 13 4 2 Anecdotal reports of a feeling of low blood sugar could be explained by insulin resistance preventing muscle cells taking up glucose despite test results showing high blood glucose levels Several McArdle people have reported on online chat groups that they experience a feeling of low blood sugar levels If these people have insulin resistance a feeling of low blood sugar could occur because the insulin isn t able to act and the cells aren t able to take up glucose even though there are high glucose levels in the blood If this was the case blood test results would show high blood sugar levels but the McArdle person would feel that they had low blood sugar Although studies have shown that some McArdle people have insulin resistance these studies did not ask McArdle people whether they felt that their blood sugar levels were low If this were the case I wonder whether insulin resistance could lead to weight gain in McArdle people If McArdle people have a feeling of low blood sugar this would make the person want to eat a high sugar or high carbohydrate food If the muscle cells are unable to take in glucose the muscle will not be able to use the glucose to provide energy for movement Instead this excess glucose would be stored as glycogen or as fat This is an unproven theory Weight gain should be avoided by McArdle people see section 4 2 3 13 4 3 Exercise can be used to prevent and treat insulin resistance in people unaffected by McArdle s People unaffected by McArdle s are less likely to develop type 2 diabetes if they have a physically active lifestyle In people unaffected by McArdle s an increase in abdominal fat accumulation and loss of muscle mass are highly associated with the development of insulin resistance Ivy 1997 Exercise burns this fat can prevent muscle wastage and stimulate muscle development Hawley 2008 found that in studies of people unaffected by McArdle s who have type 2 diabetes even a single bout of exercise can increase the amount of glucose taken up into the muscle cells In this case the glucose is taken up in a different way which is stimulated by exercise However the authors say that this effect will only last for approximately 48 hours In contrast repeated physical activity i e exercise training results in a persistent increase in insulin action in skeletal muscle of obese and insulin resistant individuals In addition they found that regular training seemed to increase the ability of the muscles to use fat for energy Page 148 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Exercise has been reported as beneficial for McArdle people see section 4 2 2 but at present no research has been carried out to see whether exercise could be used to treat McArdle people with insulin resistance 13 4 3 1 Research suggests that a sugary drink before exercise can be effective even in McArdle people with insulin resistance but should only be used under medical supervision Although sugary drinks are not recommended for people with diabetes see important note below they have been experimentally tested on two McArdle people who also had insulin resistance NIDDM These tests were performed under close medical supervision Vissing and Haller 2003 tested a McArdle person with NIDDM They found that a sucrose drink was equally effective in this person as in McArdle people who did not have NIDDM Similar experimental results had been previously found by Yamuchi et al 1996 who found that a McArdle person with NIDDM was able to take up and use glucose from the blood during exercise Yamuchi et al struggled to explain this observation but Vissing and Haller suggested that glucose uptake in these McArdle people with NIDDM may have been induced by muscle contractions not by insulin sensitivity IMPORTANT People with diabetes are not recommended to have sugar or sugary drinks McArdle people with diabetes should obtain medical advice before using sugar or sugary drinks 13 5 There is no evidence that McArdle s may increase the risk of heart problems The heart muscle in unaffected people has a 50 50 mixture of brain glycogen phosphorylase and muscle glycogen phosphorylase Miranda et al 1979 Bresolin et al 1983 Although McArdle people do not have muscle glycogen phosphorylase brain glycogen phosphorylase is present The presence of brain glycogen phosphorylase in the heart appears to be sufficient for it to function normally and heart problems are not generally reported in McArdle people In McArdle people an increased very rapid heart rate is seen during intense exercise before the second wind This response to exercise is discussed further in section 6 4 4 The increased heart rate during exercise is only seen for a short period and when the muscle pain causes the McArdle person to stop and rest the heart rate becomes lower I have heard a suggestion that as McArdle people are not able to maintain a high heart rate during exercise which is normally recommended for people unaffected by McArdle s this may lead to an increased risk of heart disease or increased cholesterol Perez et al 2006 reported a case of a 78 year old McArdle man who had had coronary heart disease However this single case report is not sufficient evidence to support this theory Nicholls et al 1996 reported a case of a 66 year old McArdle man with angina Angina is pain in the heart which is caused by narrowing of the arteries of the heart This narrowing can reduce blood flow This narrowing can be caused by several factors one of which is cholesterol Anti cholesterol drugs called statins may therefore be prescribed but these should be avoided if possible by McArdle people see section 12 1 1 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 149

13 6 McArdle s is not reported to cause liver disease but can have an effect on the results of blood tests for liver disease There is no published data that McArdle s can cause to liver disease Liver disease can be shown by an increase in the levels of proteins called Alanine Transaminase ALT formerly called SPGT and Aspartate Transaminase AST formerly called SGOT which can be detected by a blood test However skeletal muscle cells also contain AST and ALT If muscle damage has occurred raised AST and ALT levels may be seen Tuzun et al 2002 reported a case of a McArdle person who had raised levels of transaminases in the blood Measuring creatine kinase levels in the blood could indicate if muscle damage has occurred Note Raised AST and ALT levels can be caused by taking drugs viral hepatitis or excessive alcoholic consumption so if you are treated by a family doctor unfamiliar with McArdle s you may have to explain that McArdle s could also cause this result Page 150 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

14 McArdle s specialists and family doctors Because McArdle disease is rare many McArdle people find it difficult to get accurate and reliable advice on all aspects of McArdle disease including diet exercise and lifestyle They may find it very helpful to have a consultation with a medical professional who has specialised knowledge of McArdle disease The primary benefit of visiting a McArdle specialist is that they are familiar with the disease and hopefully have met a large number of McArdle people giving them an overview of common differences in McArdle symptoms between men and women and common changes with age They also may have noticed other secondary problems or complications for example gout McArdle specialists may be able to confirm the diagnosis of McArdle s offer advice on how to reach second wind and update you on current treatments They should also be able to discuss with you how to deal with problems caused by McArdle disease such as myoglobinuria and contractures McArdle specialists often have a strong interest in other similar muscle diseases or glycogen storage diseases and this can have an additional benefit in that they may be aware of new advice or information which could also be applied to McArdle disease Most of the time McArdle people will consult their family doctor for medical advice including advice on problems or complaints which are unrelated to McArdle disease Anecdotally many McArdle people report that their family doctor does not know very much about McArdle s As well as being aware that McArdle disease may make you slightly more likely to have some other diseases conditions such as gout and symptoms similar to insulin resistance it is also important to remind your family doctor that not all problems and symptoms will be due to McArdle disease Keeping your own record of medical investigations and treatments test results CK values medications etc can be helpful to allow you to monitor your progress over time and for reference if you change family doctor or McArdle specialist The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 151

14 1 McArdle specialists There are several medical professionals who have a strong interest and specialise in McArdle disease Some of them are listed below The McArdle clinic in London is the only McArdle s clinic in the UK McArdle people in the UK must be referred to the McArdle clinic by their family doctor Further information about the clinic and obtaining a referral is available from the AGSD UK website It is sometimes possible for McArdle people in Ireland to also visit this clinic In the USA the Muscular Dystrophy Association MDA is able to put people in contact with specialists who are located nearby Many of the McArdle s specialists carry out research into McArdle s and run clinical trials as well as seeing patients in a clinic There are some differences in opinion between McArdle s specialists such as what is the ideal diet for McArdle people see section 6 6 and so the advice you receive may not be exactly the same from each specialist 14 1 1 Benefits of visiting a McArdle specialist Visiting a McArdle s specialist can be of great benefit to McArdle people Unlike your family doctor McArdle s specialists have a much more thorough understanding of McArdle s McArdle s specialists may be able to Confirm the diagnosis of McArdle s is correct Teach you how to reach second wind Provide you with information about the usual symptoms and variations of McArdle disease Guide you with physiotherapy and advice on diet Tell you about current treatments and recent research Provide genetic counselling as appropriate Recruit you for clinical trials into treatments for McArdle s Provide you with a letter note instruction sheet with information about McArdle s to take into hospital and show the doctors and nurses if you require emergency treatment for example for severe muscle damage Devise a personal treatment plan for if you suffer an episode of myoglobinuria Myoglobinuria is the most obvious sign of muscle damage which can be assessed by eye without any medical tests You should discuss whether a low level of myoglobinuria could be treated at home for example by drinking plenty of fluids or whether you should go to a hospital each time Anecdotally this seems to vary from person to person but any decision to treat myoglobinuria at home should be made in consultation with a medical specialist Discuss how to treat contractures whether they will prescribe a strong painkiller anecdotally McArdle people say that normal painkillers often are not strong enough to treat the pain of a contracture If strong painkillers are prescribed they should provide clear instructions about when and how to take the drug e g how many pills how often and Page 152 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

whether it is safe to take with any other drugs you take Also whether it would affect your ability to drive or operate machinery 14 1 1 1 The UK McArdle clinic The McArdle s clinic at London is one of the few McArdle s clinics in the world It was previously located at the RJAH Orthopaedic Hospital in Oswestry Shropshire and in 2010 it was relocated to the National Hospital for Neurology and Neurosurgery London WC1N 3BG I attended the clinic while it was located in Oswestry several times between the years of 2005 and 2008 as an observer where I was able to sit in on consultations between patients and Dr Quinlivan and other members of the team The clinic offers McArdle people an opportunity to meet specialists from several disciplines Dr Ros Quinlivan is one of the leading McArdle s specialists She primarily sees patients but is also involved in clinical trials and in collaborations with other people carrying out research into McArdle s around the world Other members of the multi disciplinary clinic include a physiotherapist who specialises in neuromuscular conditions a dietician and an exercise physiologist who can measure the ability to exercise and help people learn to reach second wind Dr Quinlivan also runs clinics for other muscle diseases so her team are experienced at dealing with people with muscle diseases and any associated problems 14 1 2 Paying to see a McArdle s specialist In the UK referral to the McArdle clinic is made under the National Health Service NHS The patient does not have to pay for the consultation although it may be necessary to pay for any prescriptions required In many other countries patients must either pay for their consultation or have a health insurance policy which will cover the cost Anecdotally patients report that some McArdle s specialists do not accept health insurance payments for consultations It would be sensible to enquire about how to pay for the consultation and whether health insurance payments are accepted prior to arranging an appointment 14 2 Your family doctor how to help them treat you what information to give them what to remind them 14 2 1 Your family doctor may not know very much about McArdle s Many McArdle people anecdotally report that their family doctor does not know very much about McArdle s I would suggest that you ask your family doctor to obtain and read the medical paper McArdle disease what do neurologists need to know by Alejandro Lucia Gisela Nogales Gadea Margarita P rez Miguel A Mart n Antoni L Andreu and Joaqu n Arenas This is a very useful and informative and relatively short paper which summarizes most of the key information about McArdle s 14 2 2 Important things to remind your family doctor You should check with your family doctor that any prescribed medicine does not have the side effect of rhabdomyolysis see section 5 If it does have this side effect you must decide together with your family doctor how to monitor for or reduce the risk of The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 153

rhabdomyolysis One approach would be frequent measuring of creatine kinase levels in the blood to check for muscle damage That a raised CK level even at rest is usual for McArdle people see section 5 3 2 1 That muscle damage could lead to an increase in the AST and ALT levels and so high levels of these proteins in the blood is less likely to indicate liver damage see section 13 6 McArdle disease may make you slightly more likely to have certain other diseases conditions such as insulin resistance see section 13 4 or gout see section 13 1 14 2 2 1 It s not all about McArdle disease It is also important to remember that not all problems or symptoms will be due to McArdle disease If a person has McArdle s their family doctor may assume that any other symptom or disease is due to McArdle s However unless there is a well known relationship between McArdle s and the second problem disease then it is important that the second problem is investigated thoroughly and treated appropriately You may have to remind your family doctor that other symptoms or problems could be completely unrelated to McArdle s 14 3 Become your own personal expert on McArdle s If you have an on going medical condition such as McArdle disease it can be very helpful to keep your own record of medical investigations and treatments you have This can be particularly useful if you see different specialists over time Or if you move house or country you may need this information to tell your new family doctor You may also find it helpful to write relevant ideas in your notebook for future reference for example if you hear something relating to McArdle s in the media or on a chat group Information to make a note of could include Tests that were performed and the results for example if you regularly have your CK levels measured in blood tests over time you will find out what level is normal for you If the CK level is higher than usual it might be helpful to note what activity you were doing before the test was done Medicines you are prescribed Once you have finished a course of medicine you could stick the medicine box or information leaflet into your notebook Useful information to note could include manufacturer the active ingredient s or all ingredients the trade name of the product the date you started taking and finished taking the medicine If you have positive effects it cured the problem or negative effects like side effects Similar notes could be made if you decide to try supplements or herbal medicines or to alter your diet or exercise regime although you should consult your FAMILY DOCTOR prior to any of these Everyday differences For example if you go for a walk on the beach and have severe contractures later that day this could be noted in the notebook Or if you find that your symptoms are better in summer or winter Page 154 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Keeping notes like these can help you to see how the disease is progressing for example whether it gets worse as you get older or remains constant It can be useful to have a record of different treatments you have tried and to see which had beneficial or negative effects Online resources There is further information about the UK McArdle clinic on the AGSD UK website http www agsd org uk tabid 1143 default aspx Contact details for McArdle specialists in the USA are available via the Muscular Dystrophy website http www muscular dystrophy org The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 155

Page 156 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

15 Models of McArdle s can be used to test treatments Animals with McArdle disease or cells in the laboratory which mimic the disease are known as models Models provide a useful way to test potential treatments This is safer than giving the treatments humans in case the treatments cause negative side effects For many other muscle diseases it is possible to use muscle cells obtained from a muscle biopsy from a person with the disease These muscle cells can be grown in a laboratory and used to test the effects of potential treatments Unfortunately this technique does not work very well for McArdle disease Once muscle cells are removed from the body they stop trying to produce muscle glycogen phosphorylase Muscle cells from people unaffected by McArdle disease produce muscle glycogen phosphorylase at high levels in the human body but produce very low levels once they are removed from the body This means that muscle cells from McArdle people can t easily be used in a laboratory to test a treatment because even if a successful treatment was found which enabled the mutant muscle glycogen phosphorylase to become functional the muscle glycogen phosphorylase would not be produced A secondary problem is that cells grown in the laboratory begin to produce the brain and liver glycogen phosphorylase which are so similar that it is hard to detect whether a treatment has caused an increase in the amount of the muscle glycogen phosphorylase Animal models of McArdle disease are therefore particularly valuable McArdle disease has been found to occur naturally in sheep and also in cattle As in humans sheep and cattle also inherit McArdle s as an autosomal recessive disease Animals also have a reduced amount of muscle glycogen phosphorylase and an accumulation of glycogen in the muscle cells In a similar way to humans sheep with McArdle s sheep also struggle to exercise These animals have the potential to be used for scientists to learn more about McArdle s and also to test possible treatments It is very useful to be able to test the effect of treatments within the body for example to test whether an oral treatment will be carried around the body in the bloodstream and taken to the muscles The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 157

15 1 Models can be used to test potential treatments Many researchers are interested in developing treatments for McArdle s It is often not sensible to test treatments directly on humans in case they may produce bad side effects or not even work During the development of a treatment initial trials are usually performed on cells which have been made to mimic the disease If positive results are seen the treatment is then tested upon animals with the disease usually mice but occasionally birds or other animals If positive results are seen and no or few bad side effects the treatment may then be tested upon humans Cells which have been made to mimic the disease and animals with the disease are usually known as models Animal models of McArdle disease could provide valuable information about the disease and offer a valuable opportunity to test out possibly forms of treatment There are two existing whole animal models of McArdle disease which are Charolais cattle Angelos et al 1995 and Merino sheep Tan et al 1997 Both of these animal models have occurred naturally These animals have the potential to be used to test possible treatments which if successful could then be used to treat humans with McArdle s 15 1 1 Sheep with McArdle disease In Australia a sheep model of McArdle disease has been identified Tan et al 1997 The mutation is a bit complicated as it is G to A mutation in the introns 19 3 splice site which leads to a new splice site 8 base pairs into exon 20 This causes a frame shift scrambling of 18 amino acids and t hen a premature truncation of the enzyme removing 31 amino acids from the C terminal of the protein Basically the amino acid sequence gets mixed up at the end and is shorter than usual In the sheep the amount of Pygm mRNA is reduced and is only about 20 the level of mRNA of normal unaffected sheep carrier sheep produced almost as much mRNA as normal sheep Walker 2006 McArdle sheep do not have any functional muscle glycogen phosphorylase Tan et al 1997 Walker 2006 Not even non functional muscle glycogen phosphorylase protein can be detected from McArdle s sheep Walker 2006 It has also been found that the McArdle s sheep have exercise intolerance are unable to run Carrier sheep do not appear to demonstrate McArdle symptoms of difficulty with exercise or myoglobinuria Walker 2006 A muscle biopsy showed the absence of functional muscle glycogen phosphorylase and increased glycogen storage Tan et al 1997 Walker 2006 found that carrier sheep have approximately 45 of normal levels of glycogen phosphorylase and Tan et al 1997 found carrier sheep had 24 62 of normal levels of glycogen phosphorylase 15 1 2 Cows with McArdle disease In 1995 six Charolais cows were described with rhabdomyolysis Muscle biopsies were used to show increased muscle glycogen concentrations and an absence of functional muscle glycogen phosphorylase McArdle cows have a reduced amount of muscle glycogen phosphorylase compared to unaffected cows and an increased amount of glycogen in the skeletal muscle cells Angelos et al 1995 Tsujino et al 1996 Each cow had a common ancestor from both parents suggesting autosomal recessive inheritance Angelos et al 1995 Tsujino et al 1996 identified the mutation as R490W This mutation results in detectable Pygm mRNA but a reduced amount of muscle glycogen phosphorylase Page 158 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

15 1 3 Mouse and rat models of McArdle disease Although various research groups are reported to be working on a genetically modified mouse model of McArdle disease Lucia et al 2008a none have yet been published Various physical mechanisms have been used to create a model of McArdle disease which have contributed to understanding about glycogen phosphorylase but were not used to test therapies for McArdle disease These have included injection of sodium iodoacetate in adult male rats Brumback 1980 This led to muscle cramps during exercise rhabdomyolysis elevated creatine kinase levels and damaged muscle fibres after exercise Gorin et al 1996 stopped some of the leg muscles of rats being able to contract by injecting them with botulinum toxin A which is also used for cosmetic Botox This prevented the nerve transmitting signal to the muscles to stimulate contraction for 10 12 days which then slowly recovered Baker et al 2006 used an inhibitor to inactivate muscle glycogen phosphorylase which created a model of M cArdle disease although this was not their purpose 15 1 4 Muscle cell culture from unaffected people and McArdle people Cultured muscle cells from McArdle people would be a useful model for McArdle disease These would be obtained by a muscle biopsy from McArdle people and then grown in a research laboratory When cells are grown in a laboratory this is known as cell culture These muscle cells could be used to test potential treatments Muscles cells have successfully been used to create models of many other human diseases but unfortunately it seems that it is not possible to use muscle cells as a model for McArdle s The problem is that during normal muscle development muscle glycogen phosphorylase is not usually produced by the muscle cells until a late stage in muscle development when the muscles become mature Before that immature muscles produce a different isoform brain glycogen phosphorylase which is also known as foetal glycogen phosphorylase This is also produced by immature muscle cells new cells as they regrow after muscle damage see section 6 5 4 The research into whether muscle cells will produce muscle glycogen phosphorylase in culture is confusing and contradictory Sato et al 1977 observed that cultured muscle cells from both unaffected people and McArdle people did not produce muscle glycogen phosphorylase In contrast there have been two reports of muscle glycogen phosphorylase re appearing in cultured McArdle muscle cells Meienhofer et al 1977 and Martinuzzi et al 1993 despite a lack of muscle glycogen phosphorylase in a muscle biopsy from the same McArdle people It is difficult to interpret these results in the absence of knowing which mutations were present as some mutations may allow the enzyme to be made and even have some activity If muscle cells are grown with nerve cells in culture is called innervation Growing nerve cells in the same container as the muscle cells can help the muscle cells become mature Muscle cells grown in culture without nerve cells are called aneural culture Several studies by Andrea Martinuzzi showed that only very low levels of muscle glycogen phosphorylase mRNA and enzyme are produced by normal control differentiated muscle cells in culture unless the cells are innervated with either chick or rat nerve explant Martinuzzi et al 1986 Martinuzzi et al 1988 Martinuzzi et al 1993 Some early studies were limited by lack of knowledge of the different phosphorylase isoforms lack of specific antibodies which can be used to detect and differentiate between different isoforms The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 159

and absence of knowledge of the specific mutations in each McArdle person It seems likely that some of these cases may be due to mis interpretation of the brain or liver form as the muscle form of glycogen phosphorylase DiMauro et al 1978 reported the brain isoform to be the principle isoform in cultured muscle cells from McArdle people Martinuzzi et al 1986 1993 found that about 40 of functional glycogen phosphorylase in innervated cultures and about 60 in aneural cultures was the brain and possibly liver isoform and Gorin et al 1989 found that primary rat skeletal explants expressed non muscle phosphorylase isoforms in vitro A recent study by Nogales Gadea et al 2010 reported that cultured muscle cells from McArdle s people and from people unaffected by McArdle s produced the brain and liver isoforms of glycogen phosphorylase In addition cultured muscle cells from people unaffected by McArdle s also produced a small amount of muscle glycogen phosphorylase The problems with using cultured muscle cells as a model of McArdle s are therefore Only a low level of muscle glycogen phosphorylase is produced in cultures of muscle cells from unaffected people The brain and liver isoforms are also produced by muscle cells in culture The isoforms are so similar that this makes it much harder to see whether there is a complete absence of muscle glycogen phosphorylase in cells from McArdle people and also harder to see if a treatment has caused an increase in the amount of the muscle glycogen phosphorylase Unless a special and complex procedure called immortalisation is performed muscle cells can only be grown for a certain period of time before the cells will stop growing This limits the amount of time in which experiments can be performed on the cells and would mean repeated muscle biopsies to obtain fresh muscle cells to culture 15 1 5 Creation of cell models of McArdle s My Ph D project was to create other types of cell models of McArdle s Wright 2009 These cell models were produced to overcome avoid the problems of using muscle cells At present this research is unpublished but a fuller description of the research will be included in this section at a later date 15 2 Animal and cell models can be used to test potential therapies for McArdle disease As discussed in the next section section 16 the sheep model of McArdle disease has been used to test several different potential treatments for McArdle disease The sheep model has the advantage of being a whole animal which offers the opportunity to explore and try to overcome difficulties of getting the treatment to move around the body to the muscles However the sheep are more expensive to maintain than cells in culture The cow model of McArdle disease has not been used to test any treatment probably because cows are large and it would be expensive to maintain them and to use them to test potential therapies Cell culture models have also been used to test potential therapies and these are discussed below Page 160 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

16 Potential therapies for McArdle disease Currently the best treatment available for McArdle disease is regular moderate exercise There are many other possible therapies which have been suggested Some of these have been tested in humans or in animal or cell models of McArdle s but only exercise is currently in use as a treatment for McArdle people Gene therapy would involve trying to correct the DNA sequence of the PYGM gene within each muscle cell or to provide an additional correct copy of the gene to each muscle cell Gene therapy is currently considered too dangerous for use in people except those with a life threatening disease Other treatment could include drugs which manipulate the machinery of the cell so that it ignores premature stop codons and produces full length enzyme Both Ataluren a novel drug previously called PTC124 and one family of antibiotics aminoglycosides have been shown to have this effect in some models of muscle disease which are similar to McArdle disease They require the mRNA to be present and are therefore less likely to work on certain mutations such as the very common R50X mutation where the mRNA has been destroyed by nonsense mediated decay Enzyme replacement therapy where the enzyme is given by injection into the bloodstream is unlikely to be successful for McArdle disease because it does not go into the part of the muscle cell where it is needed However an alternative approach is to use drugs for example valproate to stimulate the body to produce brain glycogen phosphorylase This version of the enzyme works in almost the same way as muscle glycogen phosphorylase and is produced in the muscle cells before birth but stops being produced in the muscle cells around the time of birth Initial trials of valproate in sheep with McArdle disease appear to have promising results although further studies are needed The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 161

16 1 Therapies to correct or replace the PYGM genomic sequence McArdle disease is caused by mutations in the PYGM gene There are several therapies which could be used to correct or replace these mutations 16 1 1 Gene therapy to provide a normal copy of the PYGM gene Gene therapy could be used to provide McArdle people with an additional copy of the PYGM gene which does not have any mutations If this gene worked well it could change the symptoms of the McArdle person to be similar to a carrier Carriers do not usually have symptoms of McArdle s Methods to put this additional copy of PYGM gene into the cells could include a kind of electric shock Yoshida et al 2004 using a modified virus called an adenovirus to put the additional copy of the gene into the body or to remove muscle cells from a McArdle person add the gene in a laboratory using an adenovirus and then put these muscle cells back into the McArdle person s body Neuwelte 1995 Adenoviruses are an attractive option because they are very efficient at putting genes into cells can easily be produced at a high concentration and have already undergone much research Parker et al 2008 However at present the risks of gene therapy make it an unacceptable treatment Possible risks of gene therapy include An immune reaction to the new protein in this case muscle glycogen phosphorylase An immune reaction to the adenovirus The new gene may be put into the genome of the cell at a location which interferes with cell growth or cell survival This could even have the effect of causing cancer There is also a worry that even though the adenovirus has been modified to make it safe it could use some of the virus DNA sequence which is naturally found in the human genome and together form a more dangerous virus The immune system is the body s natural defence system against organisms like parasites and worms bacteria and viruses such as adenovirus which may try to invade the body Although the adenovirus used for gene therapy has been inactivated so that it cannot harm the body the body may still recognise it as a virus and cause an immune reaction to try to destroy the virus An immune reaction is also more likely to occur if the body is exposed to a new and unfamiliar protein As most McArdle people do not have any muscle glycogen phosphorylase if gene therapy treatment leads to the protein being produced the body may not recognise the enzyme and may assume that it is a foreign organism This could lead to an immune reaction against the enzyme This is discussed further in section 16 3 2 At present gene therapy is only being tried on people with a life threatening disease X linked SCID SCID X1 is an inherited disease which causes children to not have any immune system to protect them from everyday colds bacteria and viruses Children with SCID X1 are sometimes called bubble boy bubble girl Schwarzwaelder et al 2007 carried out a trial where ten children with SCID X1 were treated with a kind of modified virus called gammaretrovirus mediated to provide them with a normal copy of a gene to treat the disease The treatment improved their immune system without any serious adverse events for at least 5 years after treatment However more than 9 months after treatment some of the cells from the treated children were examined It was found that in some cases the retrovirus had inserted itself into the genome of the cells in areas which Page 162 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

contained important genes The insertion of the retrovirus may have disrupted genes which were necessary for cell survival and growth Gene therapy for McArdle disease by providing an additional normal copy of the PYGM gene involves the new copy being inserted into a random location of the genome in the cell However it is most likely to be inserted into a region of the genome which the cell is using at the time Berns and Linden 1995 Some genes help to prevent cancer these are called tumour suppressor genes and if the new copy of PYGM was inserted into this gene and stopped it working it could increase the risk of cancer Temin 1998 It is also possible that the PYGM gene could integrate into a different important gene and inactivate it Nienhuis et al 2006 It is impossible to predict the outcome if an essential gene was inactivated The risks make gene therapy a currently unacceptable treatment for McArdle disease Gene transfer has been tried on some cell based models of McArdle disease Baque et al 1994 used an adenovirus vector to introduce mouse muscle glycogen phosphorylase into mouse muscle cells which had been grown in culture for a very long time this type of cells was called C2C12 cell line The amount of muscle glycogen phosphorylase mRNA and the amount of functional muscle glycogen phosphorylase increased in the cells for up to 20 days An adenovirus containing full length human muscle phosphorylase has been put into muscle cells cultured from McArdle human and sheep muscle The authors claimed that this led to production of muscle glycogen phosphorylase suggesting this procedure could be tried in muscles of McArdle people Pari et al 1999 However I think that the results are questionable as the antibody was reactive against all isoforms and would also have detected the liver and brain isoforms of glycogen phosphorylase which would normally be expressed by the muscle cells in culture see section 15 1 4 16 1 2 Targeted correction of mutation within the PYGM gene Rather than adding a whole new copy of the PYGM gene as described in section 16 1 1 it may also be possible to specifically correct the mutation in the gene This is called in vivo gene correction In vivo gene correction would be an alternative approach to replacement gene therapy Thorpe et al 2002 and because it would correct the PYGM gene it would provide a long term cure The major benefit of correcting a defective copy of a gene in situ in the genome is that once it has been repaired the cell could control how much of the enzyme to make in the normal way It would be a permanent cure because the corrected gene will be passed on during cell growth and division Methods to specifically correct the mutation are complicated but basically involve putting a short stretch of DNA into the cell which contains the correct sequence The cell then uses this as a template to correct the gene within the genome by a process known as homologous recombination Sometimes a bit of protein called a carrier peptide can be added to the end of this DNA to stimulate the cell to use it to repair the gene Svasti et al 2009 An alternative technique uses specific enzymes which cut up the DNA This stimulates the cell to repair and correct the gene Some proteins called zinc finger nucleases can be used to direct correction and homologous replacement of a region of a gene Paques and Duchateau 2007 Problems with current gene correction strategies include the difficulty in carrying this out in all the cells of a whole animal as the process doesn t work very well it was found to correct DNA in less than 0 1 of the cells in a mouse model of Duchenne muscular dystrophy Kapsa et al 2001 It The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 163

may be necessary to put the short stretches of DNA in to the cells many times Kapsa et al 2001 There is also a risk that the short stretches of DNA could interfere with other genes possible stopping them working and the long term risks are currently unknown Gene correction has been used successfully in several animal models of disease correction of a zebrafish model of Menkes disease using antisense oligonucleotides Madsen et al 2008 correction of a mouse model of Pompe Disease GSD II by modified single stranded oligonucleotides Lu et al 2003 and correction of the mdx mouse model of Duchenne muscular dystrophy using single stranded short fragment homologous replacement Kapsa et al 2001 16 1 2 1 An in vivo trial of gene therapy in the sheep model of McArdle disease Gene replacement using an adenovirus has been tested in the sheep model of McArdle disease McC Howell 2006 Two different types of adenovirus which had a copy of human PYGM gene were injected into skeletal muscle of McArdle s sheep The injection caused some muscle damage which also led to expression of the brain and liver isoforms by regenerating immature muscle cells Muscle cells which had been injected with the adenovirus did produce functional muscle glycogen phosphorylase Although this appeared to be very successful the production of muscle glycogen phosphorylase was limited to the region of the injection and did not spread to other regions of the muscle As suggested by the authors a method of getting the adenovirus into all regions of the body would be required 16 2 Therapies to read through mutations in the mRNA transcript to produce full length muscle glycogen phosphorylase 16 2 1 Read through of premature stop codons by aminoglycoside drugs More than 1800 inherited human genetic disorders up to 70 of individual cases can be caused by premature stop codons Kellermayer 2006 Welch et al 2007 usually resulting in lack of protein Premature stop codons can also produce shortened truncated proteins which can cause disruption in the cell and sometimes cause a disease Frischmeyer and Dietz 1999 Aminoglycosides are a group of antibiotics already used in humans Aminoglycoside antibiotics can bind to different parts of the ribosome and interfere with the production of protein At a low level this can be used therapeutically to allow the ribosome to ignore and read through premature stop codons resulting in production of full length protein However at a higher concentration this may interfere with protein production leading to cell death Wolstencroft et al 2005 tested six aminoglycosides geneticin gentamicin lividomycin streptomycin tobramycin and amikacin in a cell model of Spinal Muscular Atrophy Spinal Muscular Atrophy is a disease caused by the lack of several SMN proteins They found that two of the aminoglycosides caused read through of premature stop codons which increased levels of the SMN protein Kimura et al 2005 treated muscle cells which were a cell model of Duchenne muscular dystrophy with gentamicin which caused read through of a premature stop codon mutation in the dystrophin gene A premature stop codon the codon is TGA causes the R50X amino acid mutation in about 80 of UK McArdle patients DiMauro et al 2002 It is possible that aminoglycosides could be used to read through the premature stop codon and produce full length functional muscle glycogen phosphorylase Schroers et al 2006 tested whether gentamicin could be used as a treatment to Page 164 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

enable read through of R50X and R270X premature stop codons in the PYGM gene in McArdle patients They treated four patients with gentamicin sulphate at 8mg kg day intravenously for 10 minutes each day for 10 days No increase in amounts of functional phosphorylase was seen with gentamicin in the experiments in McArdle people Possible explanations for this lack of success could be A the wrong amount of gentamicin was used Further studies using various different amounts of gentamicin could be performed to find out which concentration is best B The treatment needs to be continued for longer It is not known how quickly the muscle cells would begin to respond to gentamicin It may be that a longer period of treatment would be needed Further studies could include giving McArdle people the treatment for longer periods of time C Perhaps the biggest challenge in treating patients with the R50X mutation is caused by an absence of mRNA for the treatment to work on Read through therapies such as aminoglycoside drugs and also PTC124 Ataluren require PYGM mRNA to be present See section 3 1 for an explanation of mRNA However it is known that PYGM mRNA which has the R50X mutation is destroyed by a process called nonsense mediated decay Nonsense mediated decay is explained further in section 3 2 1 1 If the mRNA is destroyed then there is nothing available for the aminoglycoside treatment to act upon Only some mutations only premature stop codons are destroyed by nonsense mediated decay and more may be identified in the future At the moment it is know that the R50X mutation is destroyed by nonsense mediated decay but it is not known whether the R270X mutation is affected by nonsense mediated decay too If both PYGM mRNA with either R50X or R270X mutations are destroyed by nonsense mediated decay then that could explain why the gentamicin treatment did not work in the McArdle people tested Schroers et al 2006 also took muscle cells from one person and tested them with different concentrations of gentamicin zero 400 or 1000ug ml for 5 days No increase in amounts of functional phosphorylase was seen with gentamicin in either the experiments in people or in cells However this experiment was flawed because they didn t get muscle cells from a person who was unaffected by McArdle s and show that muscle glycogen phosphorylase was produced in culture It is therefore not possible to determine whether the lack of results was because a muscle glycogen phosphorylase is not produced by cells in culture even when the cells are from unaffected people or b gentamicin treatment did not produce an increase in muscle glycogen phosphorylase The problems with trying to use muscle cells as a model of McArdle s are discussed in section 15 1 4 One worry would be whether an aminoglycoside would read through the stop codons which are naturally found at the end of a gene These natural stop codons play an important role in telling the ribosome that it has reached the end of making a protein The good news is that aminoglycosides seem to work better on premature stop codons and have less effect on natural stop codons Aminoglycosides are unlikely to read through the natural stop codon of the gene because there are often multiple stop codons A new drug called Ataluren formerly called PTC124 has been shown not to read through multiple stop codons Welch et al 2007 16 2 1 1 The future of read through drugs Ataluren also called PTC124 Before Ataluren was developed gentamicin had been the most promising aminoglycoside drug and read through experiments had been done in the mdx mouse model of Duchenne muscular dystrophy and in the mouse model of cystic fibrosis However gentamicin was not highly effective and had damaging side effects because it was toxic and damaging to the kidney and ear An additional problem was that gentamicin had to be injected into the areas of the body needing treatment In The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 165

contrast Ataluren could be taken orally by mouth Du et al 2008 Ataluren is not an aminoglycoside but works in a similar manner PTC124 Ataluren is a novel non antibiotic drug which promotes read through of mutant stop codons in mRNA B nnemann et al 2007 Ataluren has only mild to moderate adverse side effects which do not increase with increased dosage There are three different stop codons TAA TAG and TGA which can occur in a gene Any of them can be premature stop codons Some aminoglycosides are better at reading through one stop codon than another Ataluren was shown to be able to read through all three premature stop codons in a cell model TGA was the stop codon which was most efficiently read through by Ataluren Welch et al 2007 Ataluren has been tested on muscle cells from humans with Duchenne muscular dystrophy and on muscle cells from the mdx mouse model of Duchenne muscular dystrophy In these muscle cells Ataluren was able to read through a premature stop codon so that dystrophin was produced Ataluren also helped to improve muscle function after 2 8 weeks of treatment when given to the mdx mice Welch et al 2007 Ataluren was found to read through the G542X premature stop codon mutation in a mouse model of cystic fibrosis This resulted in production of the CFTR protein Mutations in the CFTR protein can reduce the chloride currents in humans and mice with cystic fibrosis When mice with cystic fibrosis were treated with Ataluren their chloride currents were increased to 24 29 that of normal mice Du et al 2008 Ataluren is still in development but could be a promising potential treatment for McArdle disease however premature stop codons such as R50X often induce nonsense mediated decay which causes rapid destruction of PYGM mRNA A read through drug would need to protect mRNA from nonsense mediated decay to allow it to remain present for long enough for the ribosome to read through the stop codon and produce full length protein There have been no published data to suggest that Ataluren may stabilize mRNA or protect it from nonsense mediated 16 2 2 Therapeutic exon skipping As discussed in section 17 4 splicing occurs to mRNA whereby the coding regions exons are spliced joined together and the non coding regions introns are discarded Exon skipping can be done by adding a short stretch of DNA called an oligonucleotide This can be used to help the cell to ignore an exon which contains a mutation and remove it during splicing One form of therapy for diseases caused by a single premature stop codon mutation or a single missense mutation is to skip avoid the exon which contains the mutation This form of therapy is not suitable for some other forms of genetic disease such as increased triplet repeats like Huntingdon s Disease Structural proteins act as building blocks to provide structure to the cell Exon skipping appears to be successful in genetic diseases caused by mutations in structural proteins Duchenne muscular dystrophy DMD is caused by mutations in the dystrophin protein which lead to a loss of protein in the muscle cells Dystrophin is a long protein with many exons The aim of exon skipping is to skip past the exon with the mutation so that an almost full length functional protein can be produced The protein that is produced as the results of this exon skipping is sufficient to function and to reduce the severity of the disease Enzymes are proteins which change something from one thing to another Exon skipping does not seem to be a successful way to treat genetic diseases caused by a mutation in an enzyme Many enzymes including muscle glycogen phosphorylase must form specific shapes to be functional Page 166 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Mutations at almost any place in the amino acid chain of muscle glycogen phosphorylase prevent correct formation or functioning of muscle glycogen phosphorylase For example skipping the first exon of PYGM which contains the R50X mutation would seem a likely target to treat McArdle disease but it contains Serine 15 an essential binding site for the enzyme It therefore seems that exon skipping would not be a suitable therapy for McArdle s Fernandez Cadenza et al 2003 reported a McArdle person who had the Y573X premature stop codon and the K608K silent mutation Some of the mRNA with the K608K mutation had skipped did not contain exon 15 of PYGM This mRNA could be a natural example of exon skipping However no functional muscle glycogen phosphorylase was detected in this McArdle person This natural experiment suggests that exon skipping wouldn t work for McArdle people 16 3 Therapies to replace absent muscle glycogen phosphorylase within skeletal muscle cells 16 3 1 Upregulation of an alternative isoform such as brain foetal glycogen phosphorylase It may be possible to alleviate symptoms of McArdle disease by upregulating the production of the brain or liver isoform of glycogen phosphorylase in the skeletal muscle cells Within mature skeletal muscle cells the expression of many genes including foetal genes is prevented The DNA containing these genes is tightly wound around proteins called histones the DNA is like cotton wrapped around cotton reels While the DNA is tightly wound around the histones the cell cannot use the genes to make proteins Valproate valproic acid is an enzyme which can help the DNA to become unwound and detached from the histones Once the DNA is unwound the cell can use the genes to make proteins In adult human skeletal muscle foetal brain glycogen phosphorylase is not produced Theoretically treatment with valproate could cause the DNA to be unwound so that the cell can use the brain glycogen phosphorylase DNA to make brain glycogen phosphorylase Brain glycogen phosphorylase could then replace muscle glycogen phosphorylase in the muscles of McArdle people Valproate is commonly used as an anti epilepsy drug which stabilises electrical activity in the brain and is already approved for use in humans Valproate is now being trialled therapeutically for several muscle diseases such as spinal muscular atrophy SMA Tsai et al 2008 DMD Gurpur et al 2009 and amyotrophic lateral sclerosis ALS Rouaux et al 2007 16 3 1 1 Trials of valproate and notexin in the sheep model of McArdle disease A trial was carried out whereby valproate or saline was injected into the muscles of McArdle sheep by Howell et al Saline is salt solution in water It is used as a placebo as it is not known to have any effect Nine days after the injection there were 2861 muscle fibres which were expressing phosphorylase in the muscle which had been injected with valproate There were 283 muscle fibres expressing phosphorylase in the muscle injected with saline Since this could have been due to physical injury from the needle an oral trial was carried out McArdle s lambs were given a drink of valproate similar to the way in which humans take valproate Preliminary results indicated that phosphorylase was present in some of the fibres Howell 2008 This treatment has a lot of promise as a therapy for McArdle s but further experiments will be needed to determine whether valproate also activates other proteins which could have a negative effect The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 167

Notexin a toxin from the tiger snake damages muscle fibres leading to regeneration Regenerating fibres express the foetal brain isoform of glycogen phosphorylase but once they are mature they stop expression of the foetal isoform and switch to expression of the muscle isoform Trials were carried out by injecting notexin into muscles of the McArdle s sheep Brain and liver isoforms of glycogen phosphorylase were expressed McC Howell 2008 due to damage from either the notexin or physical damage from the injection The expression of the brain and liver isoforms of glycogen phosphorylase improved the strength and fatigueability of the muscle fibres in the treated McArdle sheep although not totally This is not a very practical form of treatment for McArdle people as it would involve the use of a toxin which damages muscles and would involve frequent injections throughout skeletal muscles 16 3 2 Enzyme replacement therapy More than 3 500 people across the world have received enzyme replacement therapy and have subsequently had a better quality of life Weinreb et al 2005 At present enzyme replacement therapy ERT is available for three lysosomal diseases Type 1 Gaucher Disease GD1 Fabry Disease Hunter syndrome MPS II and also Maroteaus Lamy syndrome MPS VI It is also available for Glycogen Storage Disease II Pompe disease An account of the development of ERT is given in the film Extraordinary Measures produced by CBS Film Company and first shown in 2010 This film is about the development of enzyme replacement therapy ERT as a treatment for Pompe disease Diseases caused by the lack of an enzyme in the lysosome can be corrected by ERT The replacement enzyme is manufactured by a drug company One method is to put the gene for that enzyme into special cells in a laboratory which then use the gene to produce lots of enzyme The enzyme is then purified and infused into the patient The enzyme is taken around the body in the bloodstream and then taken into muscle cells When muscle cells take up proteins from the bloodstream they usually put them into the lysosome The lysosome is like the recycling centre of the cell Diseases caused by the lack of an enzyme in the lysosome can be treated because the cells take up the enzyme from the bloodstream and transport it into the lysosome The lysosome is the desired location for the enzyme so it treats the disease Myozyme manufactured by Genzyme is a form of ERT which is given as an intravenous injection Myozyme provides human acid glucosidase which is lacking in GSD II Pompe disease This was the first example of ERT to skeletal muscle This therapy has aided cardiac muscle and extended the life of infant patients but has been less effective in skeletal muscle than hoped It was successful in decreasing the amount of glycogen stored in the skeletal muscle Schoser et al 2008 Gaucher disease is an autosomal recessive lysosomal storage disease caused by a deficiency in glucocerebrosidase enzyme Recombinant human replacement enzyme Cerezyme made by Genzyme is given intravenously and reduces the symptoms Weinreb 2008 Laronidase enzyme replacement therapy has been used for MPS I since 2003 and recombinant arylsulfatase B Naglazyme made by Biomarin Bailey 2008 used for MPS VI since 2005 Irdurslfase Elaprase made by ShireHGT Bailey 2008 is now available for treatment for MPS II Heese 2008 These are all rare inherited metabolic disorders caused by lack of an enzyme Without treatment cell damage occurs leading to physical and mental impairment The number of diseases which can be treated with intravenous ERT is continually expanding however it is still generally restricted to defects based in the lysosome An exception is oral ERT which is used to Page 168 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

replace enzymes which are needed in the pancreas in cystic fibrosis patients Walkowiak et al 2005 Negative reactions such as anaphylactic shock tachycardia hypertension chest and throat tightness nausea vomiting rashes and headaches can occur during intravenous administration which is initially conducted in a medical setting In some Pompe patients their bodies viewed ERT as foreign and produced antibodies against the enzyme This was particularly likely if the Pompe patients did not have any enzyme not even non functional enzyme before they received ERT These antibodies made further ERT unsuccessful Schoser et al 2008 A limitation of ERT is that at present it can t cross the blood brain barrier Brady and Schiffmann 2004 Since the symptoms of McArdle disease are caused by the lack of the enzyme muscle glycogen phosphorylase one obvious form of treatment would be ERT At the moment ERT is only used to treat lysosomal storage diseases There is no published data of any enzyme therapy being tried in people with McArdle s or non lysosomal defects apart from oral treatment This may be because McArdle disease is less suitable for enzyme therapy Muscle glycogen phosphorylase is needed in the sarcoplasm cytoplasm of the muscle cells which is the wrong location for enzyme therapy In ERT the enzyme is infused into the bloodstream It is then taken up by the cells Anything which the cells take up is usually put into the lysosome where they are broken down into smaller parts for reuse ERT works for lysosomal storage diseases because the enzyme is taken into the lysosome exactly the place it is needed This would not work for McArdle disease as the enzyme is needed in a different place the cytoplasm sarcoplasm Please note the enzyme needed in Pompe disease is different to the one needed in McArdle disease At the moment no one has found a way to make the cell take up the enzyme and put it into the cytoplasm If muscle glycogen phosphorylase was given as ERT it would probably be taken into the lysosome and destroyed ERT is unlikely to be a suitable therapy for McArdle s unless a method of packaging the enzyme is developed which tells the cell to put it into the cytoplasm and not the lysosome I am not aware of any scientists working on ERT as a treatment for McArdle disease at the moment probably for the reasons I ve just outlined 16 3 3 Enzyme chaperone therapy It is likely that many of the missense mutations in muscle glycogen phosphorylase may prevent the enzyme from forming the correct structure Muscle glycogen phosphorylase with a missense mutation may have the wrong shape The cell may recognise that the structure is wrong and destroy the enzyme Some chemicals called pharmacological chaperones or active site inhibitors may be able to bind to muscle glycogen phosphorylase which contains a mutation This would probably be a chemical that was similar in shape to glucose or glycogen These chaperones may be able to help muscle glycogen phosphorylase form the correct shape This may have several benefits It may prevent the quality control system of the cell from recognising or destroying the enzyme It may also help muscle glycogen phosphorylase begin to work properly Enzyme chaperone therapy could only be used as a treatment for a person who had a missense mutation in the PYGM gene It would not work for a person who had a premature stop codon Enzyme chaperone therapy has not been tested as a treatment for McArdle s so at the moment it is only a theoretical treatment for McArdle disease However enzyme chaperone therapy has been tested for some other glycogen storage diseases The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 169

At the moment the only commercially available pharmacological chaperone therapy available is for patients with GD1 Gaucher disease and is available as an oral treatment Alfonso et al 2005 Weinreb et al 2005 Pastores et al 2009 The treatment available for Gaucher disease is called N butyl deoxynojirimycin NB DNJ Miglustat made by Actelion and is a chemical that is very similar in shape to glucose a glucose analogue A similar chemical called deoxynojirimycin DNJ may be a treatment for Pompe disease DNJ or some chemicals made from it have been found to increase the amount and activity of acid alpha glucosidase GAA in Pompe disease but this result varied depending upon the exact missense mutation Schoser et al 2008 DNJ is similar in shape to glucose so the GAA enzyme bound to it DNJ allowed the GAA enzyme to be made properly and to be functional Increasing amounts of DNJ allowed an increased amount of enzyme to be made when it contained a missense mutation but not when it contained a nonsense mutation Okumiya et al 2007 However DNJ is not yet in used as a standard treatment for Pompe disease 16 4 A discussion of research into therapies for McArdle s There are many ways in which therapies could help to reduce symptoms of McArdle s All of these are covered in this Handbook and are summarised in Table 16 1 I have included therapies which at present are only theoretical and have not yet been tested as potential treatments for McArdle s Some of these therapies have only been tested for a few different diseases at present and are relatively new For example enzyme chaperone therapy was first suggested in 1999 Ten years is a relatively short period of time for a therapy to be explored by scientists and to become a treatment used for patients Future research may reveal other phenotype modulators which have not yet been discovered It may be possible to use drugs that work with these genes in a similar way to the use of ACE inhibitors to improve symptoms of McArdle s Page 170 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Purpose of the therapy derate ise Helps to improve the ability of the heart to pump blood around the body to get more oxygen per breath and for the muscles to use energy more efficiently Quickly provide muscles Can be used 5 with energy before exercise minutes before exercise can make it easier to exercise How to get the maximum A diet high in amount of energy from food carbohydrate and you eat and ensure enough moderate in protein is eaten for muscle protein growth Various Low dose creatine supplements may help No other supplements shown to help May increase the amount of No glucose taken from the recommendations bloodstream into the at present muscles to give muscles energy Helps to improve the ability of the heart to pump blood around the body to get more oxygen per breath and for the muscles to use energy more efficiently Quickly provide muscles Can be used 5 with energy before exercise minutes before exercise can make it easier to exercise A diet high in How to get the maximum amount of energy from food carbohydrate and you eat and ensure enough moderate in protein protein is eaten for muscle growth Various Low dose creatine supplements may help No other supplements shown to help May increase the amount of No recommendations glucose taken from the at present bloodstream into the muscles to give muscles energy Diet Section 6 6 Sugary drink before exercise Section 6 4 5 High dose creatine can increase muscle pain Frequent moderate aerobic exercise Section 4 2 7 and Current recommendations from recent research This is highly recommended drugs Purpose of the therapy 6 6 Having a sugary drink can lead to weight gain It Availab may reduce the ability to get into second wind Type of therapy Section of this Handbook before tion The McArdle Disease Handbook Version 1 1 1 There is still some debate about what the ideal diet is for McArdle people Not available as not enough evidence to justify its use If more research was carried out it could be available relatively quickly as it is already approved for use in humans It would only be a treatment for McArdle people who have the DD isoform of the ACE gene McArdle people would have to be genetically tested to see if this treatment was suitable for them Available now Available now This is one of the best forms of treatment for McArdle s at present High dose creatine can increase muscle pain Comments There is still some debate about what the ideal diet is for McArdle people Availab Availab It would only be a treatment for McArdle people who have the DD isoform of the ACE gene McArdle people would have to be genetically tested to see if this treatment was suitable for them Not ava enough justify researc it could relative already in hum ACE inhibitor drugs e g ramipril Sections 7 1 7 and 9 3 1 Available now How quickly is this treatment likely to be available Having a sugary drink can lead to weight gain It Available now may reduce the ability to get into second wind Current recommendations from recent research This is highly recommended Supplements Section 7 This is one of the best forms of treatment for McArdle s at present Comments py his Kathryn Birch How qu treatm availab Availab Page 171

Page 172 No recommendations at present Read through premature stop codon to produce full length enzyme No recommendations at present Add a correct copy of the PYGM gene or correct the mutation No recommendations at present Current recommendations from recent research May increase the amount of No recommendations glucose taken from the at present bloodstream into the muscles to give muscles energy Add a correct copy of the PYGM gene or correct the mutation Purpose of the therapy Kathryn Birch The McArdle Disease Handbook Version 1 1 1 Not enough research has been done It is not known whether the insulin resistance seen in McArdle people is similar or different to type 2 diabetes Not available enough evid justify its use research wa it could be a relatively qu already appr in humans Not available to be availab time The McArdle Disease Handbook Version 1 1 1 How quickly treatment li available Kathryn Birch Not available enough evid justify its use research wa it could be a relatively qu already appr in humans Page 172 Comments No recommendations at present At present this is just a theoretical treatment There are too many risks for this to be considered as a treatment If these risks could be overcome it could provide a permanent cure for McArdle s A single study of one aminoglycoside drug gentamicin found that it was not successful as a treatment for McArdle s Aminoglycoside drugs such as gentamicin are known to have side effects including causing damage to the kidney and the ear It isn t known if the full length enzyme would be functional Would not work if nonsense mediated decay destroys PYGM mRNA which has the R50X mutation Would not work on mutations which are a frameshift followed by a stop codon Read through premature stop codon to produce full length enzyme At present this is just a theoretical treatment There are too many risks for this to be considered as a treatment If these risks could be overcome it could provide a permanent cure for McArdle s A single study of one aminoglycoside drug gentamicin found that it was not successful as a treatment for McArdle s Aminoglycoside drugs such as gentamicin are known to have side effects including causing damage to the kidney and the ear It isn t known if the full length enzyme would be functional Would not work if nonsense mediated decay destroys PYGM mRNA which has the R50X mutation Would not work on mutations which are a frameshift followed by a stop codon Not enough research has been done It is not known whether the insulin resistance seen in McArdle people is similar or different to type 2 diabetes Comments Current recommendations from recent research May increase the amount of No glucose taken from the recommendations bloodstream into the at present muscles to give muscles energy Read through of premature stop codons with aminoglycoside drugs Section 16 2 1 Gene replacement therapy or gene correction section 16 1 Giving insulin as treatment for insulin resistance Section 13 4 Type of therapy Section of this Handbook Purpose of the therapy Not available as not enough evidence to justify its use If more research was carried out it could be available relatively quickly as it already approved for use in humans Not available as not enough evidence to justify its use If more research was carried out it could be available relatively quickly as it is already approved for use in humans Not available Not likely to be available for a long time How quickly is this treatment likely to be available

Purpose of the therapy Read through premature stop codon to produce full length enzyme Read through of premature stop codons with PTC124 Ataluren or drugs which work in the same way Section 16 2 1 e as not dence to g e If more Skip avoid an exon which 2 carried contains a mutation as out available producing a version of the uickly as it enzyme which isn t quite roved for full length use proic Upregulation of an drugs alternative isoform of n the glycogen phosphorylase ction which would be functional Type of therapy Section of this Handbook e Not likely ble for a long Not available as not enough evidence to justify its use If more research was carried out it could be available relatively quickly as it already approved for use in humans At present this is just a theoretical treatment Highly unlikely to work as a treatment for McArdle s No research has been done into it Valproate is already licensed for use in humans to treat epilepsy Some success has been seen in treating McArdle s sheep It is not known if it would upregulate other genes which you don t want turned on No recommendations at present No recommendations at present No recommendations at present At present this is just a theoretical treatment Highly unlikely to work as a treatment for McArdle s No research has been done into it No recommendations at present Valproate is already licensed for use in humans to treat epilepsy Some success has been seen in treating McArdle s sheep It is not known if it would upregulate other genes which you don t want turned on The McArdle Disease Handbook Version 1 1 1 Valproate valproic acid or other drugs which work in the same way Section 16 3 1 Skip avoid an exon which contains a mutation producing a version of the enzyme which isn t quite full length Upregulation of an alternative isoform of glycogen phosphorylase which would be functional Comments Exon skipping Section 16 2 2 Current recommendations from recent research No recommendations at present Kathryn Birch Not ava develo trials a treat si disease and ap use it m for clin McArd trials w show t would before availab for Mc Not like availab Not ava enough justify researc it could relative already in hum Page 173 The McArdle Disease Handbook Version 1 1 1 How qu treatm availab Kathryn Birch Hasn t been tried for McArdle s It isn t known if the full length enzyme would be functional Would not work if nonsense mediated decay destroys PYGM mRNA which has the R50X mutation Would not work on mutations which are a frameshift followed by a stop codon Page 173 Not available as still in development Clinical trials are underway to treat similar muscle diseases If successful and approved for human use it may be available for clinical trials for McArdle s These clinical trials would have to show that treatment would be successful before it would become available as a treatment for McArdle s Not likely to become available How quickly is this treatment likely to be available Hasn t been tried for McArdle s It isn t known if the full length enzyme would be functional Would not work if nonsense mediated decay destroys PYGM mRNA which has the R50X mutation Would not work on mutations which are a frameshift followed by a stop codon Comments h e of as not Read through premature dence op to stop codon to produce full e If more length enzyme uren as carried out available h uickly ame as it is roved for use Current recommendations from recent research No recommendations at present y py is this Purpose of the therapy his ikely to be

y of current future and potential treatments for McArdle s including those which are not suitable for McArdle s Informatio ormation given with references throughout this Handbook and my personal opinion Page 174 At present enzyme replacement therapy only works for lysosomal storage diseases The current method would not work for McArdle s If a method is found in future to label the enzyme so that it is taken in the cytoplasm of the muscle cells then it could be a potential treatment It has not yet been tried as a treatment for McArdle s Has not been tried as a treatment for McArdle s It is not known if a chaperone would help muscle glycogen phosphorylase fold correctly or if it would become functional Not a practical treatment as it would require inducing muscle damage Comments Current recommendations from recent research No recommendations at present Kathryn Birch Not a practical treatment as it would require inducing muscle damage Not likely to available At present enzyme replacement therapy only works for lysosomal storage diseases The current method would not work for McArdle s If a method is found in future to label the enzyme so that it is taken in the cytoplasm of the muscle cells then it could be a potential treatment It has not yet been tried as a treatment for McArdle s Has not been tried as a treatment for McArdle s It is not known if a chaperone would help muscle glycogen phosphorylase fold correctly or if it would become functional Not likely to available as method wou for McArdle No Provide a small molecule recommendations similar to glucose which at present helps muscle glycogen phosphorylase that contains a mutation fold into the correct shape and hopefully become functional Comments Not available as not enough evidence to justify its use It may take a long time to produce enough scientific evidence to justify clinical trials Not likely to become available as the current method would not work for McArdle s Not likely to become available How quickly is this treatment likely to be available The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Not available enough evid justify its use take a long t produce eno scientific evi justify clinica Page 174 The McArdle Disease Handbook Version 1 1 1 Table 16 1 A summary of current future and potential treatments for McArdle s including those which are not suitable for McArdle s Information in this table is based upon the information given with references throughout this Handbook and my personal opinion Enzyme chaperone therapy section 16 3 3 Enzyme replacement therapy section 16 3 2 Causes muscle damage Regenerating muscle temporarily produces the brain and or liver isoform of glycogen phosphorylase No An injection of functional recommendations enzyme into the at present bloodstream which would go to the muscle cells Current recommendations from recent research No recommendations at present Notexin section 16 3 1 1 Provide a small molecule No similar to glucose which recommendations helps muscle glycogen at present phosphorylase that contains a mutation fold into the correct shape and hopefully become functional Purpose of the therapy Causes muscle damage Regenerating muscle temporarily produces the brain and or liver isoform of glycogen phosphorylase An injection of functional No enzyme into the recommendations bloodstream which would at present go to the muscle cells Type of therapy Section of this Handbook Purpose of the therapy How quickly treatment li available

17 Details about this Handbook and the information in it Research papers are used as a way for scientists and medical doctors to communicate with each other the results of clinical trials scientific research or if they notice something unusual or unique in a patient Clinical trials are the only way to reliably determine whether a potential treatment for McArdle s disease really works Clinical trials can involve testing drugs but can also include testing different exercise regimes or diets such as a sugary drink before exercise to find out whether y is this the treatment has any positive or negative effect upon the participants It is ikely to be important that clinical trials are carefully planned and performed ideally so that the participants do not know if they are receiving an active drug or an inactive placebo become Researchers usually publish the results of the clinical trial as a scientific paper The results should be published whether the treatment has a positive effect negative effect or no effect This provides a method of communicating the results to other scientists and medical professionals who can use this information to decide whether become or not to give their McArdle patients the treatments described s the current uld not work This handbook is written using information which Kathryn Birch obtained mostly s from reading scientific and medical research papers as well as some text books Where possible for each statement the author s name and date of the published paper or book is given The name and date can be used to look up the full e as not information about each paper from the References list at the end of the Handbook dence to Many research papers can now be bought online from the publisher and e It may downloaded onto your computer so that the original publication can be read time to ough idence to al trials on in this table The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 175

17 1 The purpose of this Handbook The purpose of this Handbook is to clearly explain medical and scientific research so that it can be understood by McArdle people and people interested in McArdle disease The information provided is as up to date and accurate as possible but reflects current theories and opinions Future research may improve the understanding of McArdle s and change these theories Information in this Handbook is not intended as medical advice it is not intended to replace medical advice and is not intended to be a guide to treatments for McArdle s The author Kathryn Birch has no medical training and is not qualified to offer medical advice 17 2 About the author Kathryn Birch nee Wright is a scientist and has not had any medical training She studied Biology English Literature Mathematics and Music GCE A Levels at secondary school before reading for an undergraduate degree in Natural Sciences at Cambridge University UK specialising in Genetics in her final year She worked for three years as a Research Assistant in a laboratory in Berkshire learning experimental techniques She then moved to a research lab at the RJ AH Orthopaedic Hospital in Oswestry UK where she carried out a Ph D project creating cell models of McArdle disease through Keele University UK Kathryn Birch had the idea of writing this Handbook during her Ph D when she became aware that a lot of the medical and scientific research into McArdle disease was inaccessible to people with McArdle s because it was either written in complex scientific language or too expensive to obtain 17 3 How to understand references given in this Handbook A reference is the original paper or book which I have used to find out information Where possible each sentence or paragraph is referenced References given in this Handbook enable the reader to identify and read the same paper or book which I read before I wrote that sentence or paragraph This allows the reader to get more information than I provided or to check if I reported the information accurately If you think I have made a mistake please visit the AGSD UK web site at www agsd org uk and use the Contact Us page choosing McArdle Disease Handbook References are given as either Birch et al 2009 said grass is green Or Grass is green Birch et al 2009 In these examples Birch is the name of the lead author who wrote the paper or book and the date is the date when the paper or book was published The title of the paper or book can be found in the References list section 19 at the end of the Handbook References are listed alphabetically in order of the surname of the first author So for example Birch et al 2009 would be near the start of the list of references You will be able to look up the whole name of the paper or book which could look like Birch KE and Birch EK 2009 Studies of Grass Journal of plants 2 133 134 Page 176 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

You can then use these details to obtain the paper from Journal of Plants pages 133 134 This paper is located in volume number 2 This reference has been invented to serve as an example If no reference is given and it includes phrases like I think or my theory this indicates that it is my theory which has not been scientifically proven 17 4 A note about the names of the muscle glycogen phosphorylase gene mRNA and enzyme There are standard ways to write the names of the muscle glycogen phosphorylase gene mRNA and protein which are useful to know if you are reading scientific papers These are summarised in Table 17 1 Although only humans are discussed in this section animal models of McArdle disease are discussed further in section 15 For clarity in this Handbook muscle glycogen phosphorylase has been used rather than PYGM Name of the gene Names of the mRNA Name of the enzyme Humans PYGM capitals italic PYGM capitals italic PYGM capitals non italic Animals Pygm mixed case italic Pygm mixed case italic PYGM capitals non italic Table 17 1 Standard ways to write the gene mRNA and enzyme name for muscle glycogen phosphorylase correct in 2011 17 5 How to read medical scientific papers critically Rather than simply accepting everything that is stated scientific papers and other documents such as this Handbook should be read critically as the data in them and the interpretation of the results could be affected by many things some of which are outlined below 17 5 1 1 What is the date year when the paper was published New research and understanding can mean that the advice in old research papers is now inappropriate or incorrect For example in the past McArdle people were recommended not to exercise but current advice is that frequent moderate exercise is best for McArdle people Some older research papers can be hard to understand and interpret as only limited information was known at the time For example in the past some researchers did not realise that there are different isoforms of glycogen phosphorylase so they do not specify in their research paper which isoform of glycogen phosphorylase they studied which can make it hard to understand 17 5 1 2 Who are the authors Authors may be biased Not all McArdle s specialists share the same point of view They may emphasise their point of view strongly in a paper even if there is very little scientific evidence to support this view If you find more than two papers which have no authors in common but both give the same conclusion then it is likely that it is a genuine result 17 5 1 3 How good is the clinical trial Not all clinical trials are equal The best clinical trials are double blind clinical trials where neither the participant nor the researcher knows whether the participant is receiving the treatment or a placebo Single case studies are of limited use whereas multi person trials reduce the effect of any The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 177

non compliance external factors etc It is important to have good controls The placebo effect should be avoided See section 17 6 1 for further information on clinical trials 17 5 1 4 Was the result statistically significant A statistically significant result suggests that a treatment probably does cause an effect and that the changes observed are unlikely to have occurred by chance see section 17 6 6 However different statistical tests can give different results and some scientists incorrectly try lots of different tests until they find one which gives the result they want which is poor scientific technique 17 5 1 5 Errors can occur Despite several levels of proof reading before a paper is published errors can still occur For example I believe that the mutation which Hadjigeorgiou et al 2002 describe as a R207X mutation at c 808 in exon 6 is actually the R270X mutation but the authors refer to it throughout the paper incorrectly as R207X 17 5 1 6 The same person may be mentioned in more than one study As McArdle s is very rare the same person may be mentioned in more than one paper especially if they have an unusual complication It can require quite a bit of detective work to figure out if this is the case But it is important because if one individual has particularly unusual symptoms they may be reported on more than one paper If you didn t realise this or your family doctor didn t realise you may think that the symptom is much more common than it really is For example there is a case of a woman with McArdle s who has respiratory problems because the muscles involved in breathing didn t work as well as they should But she is mentioned in two papers McArdle disease presenting as unexplained dyspnea in a young woman by Voduc et al 2004 and Variable presentation of the clinical phenotype of McArdle disease in a kindred harbouring a novel compound genotype in the muscle glycogen phosphorylase gene by Paradas 2005 The clue is usually although not in this case if the two papers have one or more author in common If these two papers are taken together it suggests that McArdle disease might cause respiratory problems but in fact both are describing the same person 17 5 1 7 The numbers of the mutations have changed When reading papers about McArdle s it is important to remember that the mutation formerly known as R49X is now known as R50X The reason is as follows In the PYGM gene the DNA code and the mRNA have the first amino acid of muscle glycogen phosphorylase as methionine single letter code M This is shown in section 3 1 1 When a protein is made the methionine is used as the first amino acid of the amino acid sequence However in the process of making the enzyme the first methionine is chopped off and removed When the first scientific studies were performed on muscle glycogen phosphorylase scientists studied the enzyme and found that it had 841 amino acids At this time the mutation was known as R49X However at a much later date scientists studied the PYGM gene and discovered that there was genetic code for the first methionine even though it was chopped off in the process of making the enzyme Muscle glycogen phosphorylase is now considered to have 842 amino acids and the R49X mutation has been renamed as R50X Page 178 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

When reading papers it can be confusing trying to understand whether the mutation being described is an old one or is newly discovered I would suggest looking out for whether the old numbering scheme of R49X and G204S or new numbering scheme of R50X and G205S are being used 17 6 An introduction to clinical trials Clinical trials are an essential method of testing whether a potential treatment for McArdle s or any other disease really works Clinical trials are conducted by researchers either scientists or doctors or the two working together Clinical trials are based upon a hypothesis that a particular treatment may help to alleviate symptoms of a disease For example a theory that taking drug X may enable McArdle people to exercise for longer Clinical trials are designed to test whether this theory is correct The best clinical trials have the components described below they include a placebo are randomised are double blind and are statistically significant Although clinical trials often involve testing new or existing drugs they do not need to involve drugs Non drug clinical trials carried out on McArdle people have included prescribing regular exercise and testing a sugary drink Clinical trials must have ways of measuring whether the treatment has produced any benefit The best ways are to measure something which the participant has little or no control over Examples would include using 31P MRS to measure changes within the cells measuring heart rate or VO2 max 6 4 4 1 It is less accurate to ask participants how they feel for example whether they feel that they have much less muscle pain It can be very hard for participants to give useful and accurate answers and hard for the researchers to use this answer to determine if a treatment is working For example if the participant has just had an argument with their partner they may feel more negative about muscle pain than on a different day but this would be unrelated to a treatment The researchers carrying out a clinical trial will want to publish the results once the trial is completed The results should be published whether or not the treatment has a positive effect negative effect or no effect Positive results may lead doctors to start prescribing the treatment drug for their McArdle s patients Negative results may warn doctors to avoid prescribing the treatment drug for their McArdle s patients Often clinical trials are first done on small group of participants and if a positive effect is seen they will be repeated on a larger number of participants It is ideal to wait until a positive result has been seen in a large scale clinical trial before considering it as a conventional treatment for that disease In a rare disease like McArdle s there may not be enough people with McArdle s for large scale trials to be possible Most countries now have very strict guidelines for researchers wishing to carry out clinical trials The trials have to be approved by a committee often at the hospital where the trial would be carried out The committee will consider whether the potential side effects and risks of the treatment are worthwhile compared to the potential benefit of the treatment The researchers also have to prepare information sheets written in plain non technical language to ensure that the participants fully understand all the risks and tests involved For example that the participants are willing to give a blood sample or undertake a muscle biopsy if that is required When participants fully understand the risks and tests involved and then agree to take part this is known as informed consent In the UK and some other countries researchers are not allowed to pay participants to take part in clinical The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 179

trials although they are allowed to pay a certain amount for travel and other costs incurred by the participant in getting to the location where the trial is taking place Most trials involve comparison for example a group of McArdle people may be compared to a group of people unaffected by McArdle s A person who is unaffected by McArdle s is often described as a control in scientific papers Or a group of McArdle people may be given a treatment and compared to a group of McArdle people who were not given the treatment 17 6 1 The placebo effect During a clinical trial the control group are the group of people who do not receive the treatment and in many cases these people receive the placebo A clinical trial must be carefully planned in order to determine whether a treatment is having a real effect or a placebo effect The placebo effect is a well known phenomenon whereby some people feel that their symptoms improve even if they are given a pill with no active medicine for example a pill made of sugar or flour The placebo effect was demonstrated in a clinical trial of dantrolene sodium carried out by Poels et al 1990 some improvement was felt by one McArdle person on treatment and three McArdle people taking the placebo There are various explanations for the placebo effect Taking a placebo pill may change the way in which the person perceives their symptoms Sometimes being part of a clinical trial may make a person feel more important Having a family doctor specialist discussing McArdle s acknowledging symptoms and providing support and encouragement may lead to a more positive view of the symptoms This is why cognitive behaviour therapy CBT is sometimes used CBT can help people come to terms with symptoms and limitations of their condition even if no treatment or cure is available Some participants either deliberately or unknowingly will give the researcher the answer they think they want to hear To determine whether a drug treatment is having a real or placebo effect it is important that the people being tested are given either the real drug or a placebo which looks smells tastes like the real drug The participants should not be able to tell the difference between the placebo and the real drug If the participant doesn t know if they are receiving the placebo or real drug this is known as a blind trial In the best studies the researcher also does not know which participants are receiving the real drug or the placebo and does not find out until the very end of the experiment If the participant doesn t know if they are receiving the placebo or real drug AND the researcher doesn t know which participants are receiving each treatment it is known as a double blind trial because both the participant and researcher are blinded to the treatment If the participant and researcher don t know whether the participant is receiving the treatment or placebo this is also known as allocation concealment An open label trial is when the participant know which drug they are receiving or know if they are receiving the placebo This is not such a good trial as participants may be biased by whether or not they are receiving the treatment Sometimes it is impossible to blind the participant and the trial has to be open label One example would be a trial of diet where it would be very difficult to prevent the participant seeing whether they are receiving a high fat or high carbohydrate meal 17 6 2 Randomised trials A really good trial will be designed so that the researcher cannot unwittingly bias the outcome One way in which this could occur would be if the researcher divides the participants into two groups for Page 180 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

example so that one set can receive the placebo and the other set receive the real drug If the researcher picks which people should be in each group the researcher may not divide the people evenly one example would be to put all the women in one group and the men in the other in this case it wouldn t be possible to say if the results were an effect of the real drug or an due to differences in gender Another example would be to put all the fit people in one group and all the unfit people in the other group These are extreme examples to illustrate the problems of allowing the researcher to choose who goes into which group A much better method is to allocate each person a number and to use a computer or even draw numbers out of a hat to randomly allocate each person into a group This removes the possibility of the researcher choosing who goes into which group 17 6 3 Cross over trial A cross over trial occurs when the participants are divided into two groups let us call them group A and group B For the first period of time several days to several years depending on the study group A will receive the placebo and group B will receive the real drug The researchers will then perform tests to see if the treatments have had any effect for example on the ability of the participants to exercise There may then be a wash out period when no drug placebo is given This is to allow the amount of real drug in the body to reduce and be removed by the body In a cross over trial group A will now receive the real drug and group B will receive the placebo Further tests will then be performed A cross over trial is particularly important when there are only a small number of participants often the case in trials with McArdle people If one person was much more fit than the others this might disproportionately affect the results if no cross over was performed For example if a very fit person was put into the group taking the real drug and the real drug actually had no effect the ability of the very fit person to exercise could lead the researchers to think that the drug had helped that person exercise A cross over trial allows the researchers to compare results obtained with the real drug and placebo each in the same person 17 6 4 Single case study A single case study is when just one participant is studied Published papers are used by family doctors and scientists as a way of communicating Single case studies are sometimes reported if a new phenomenon occurs for example if it is found that a person with McArdle s had a particularly bad reaction to a drug or treatment Specialists who read the study will be aware that McArdle s may lead to sensitivity to that drug or treatment and will be aware to look out for it in the McArdle person they deal with The disadvantage of single case studies is that it is very hard to determine if a treatment will work in other McArdle people A single case study cannot determine what other factors may affect whether a treatment may work Here is an example of a result from a large scale study which could not have been obtained from a single case study The ACE gene is unrelated to the PYGM gene which encodes muscle glycogen phosphorylase see section 9 3 1 for more information on the ACE gene McArdle people and other people in the population may have either the DD DI or II genotype It has been found that the drug treatment ramipril only helps people who have the DD genotype for the ACE gene Martinuzzi et al 2007 It was only possible to find out this result because many McArdle people took part in the drug trial If only one person had taken part in a single case study it could have had The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 181

very different results For example if the one participant had the II genotype the drug treatment would not have had any effect and would probably not have been tried again A further problem with a single case study or a study with very few participants is the lack of statistical significance 17 6 5 A home trial is an alternative to a clinical trial The alternative to a clinical trial would be a trial performed at home Many McArdle people on internet chat groups say that they have carried out home trials Home trials are not planned or carried out by a researcher They will not have been assessed by a committee to decide if they have any health risks or negative effects People carrying out a home trial on themselves are likely to know whether they are taking the treatment drug or not which does not exclude the placebo effect If a home trial suggests that a treatment does work it is not sufficient evidence to prescribe the treatment to others It would be sensible to discuss any treatment drug with your family doctor before carrying out a home trial 17 6 6 Statistical significance Clinical trials are usually carried out to determine whether a treatment or drug has a positive or negative effect upon participants However it is always possible that any changes observed could have occurred by chance and be unrelated to the treatment Mathematicians have devised several statistical calculations which can be used to determine the likelihood of a change occurring by chance These calculations take into account the number of participants and how great the observed changes are The result of the calculation can be looked up in a special table to determine if the result is statistically significant These calculations are nowadays performed using a computer A statistically significant result suggests that a treatment probably does cause an effect and that the changes observed are unlikely to have occurred by chance A result may be classed as not statistically significant if there were not enough participants or if very little difference was seen between the treatment and non treatment or drug and placebo Single case studies and trials with a small number of participants are less likely to generate statistically significant results It is possible that if the trial were repeated with more participants it would generate results that were statistically significant An example of a statement in a paper is given below Lucia et al 2008b performed some tests to look at the amount of cytokines in the blood of patients McArdle people compared to controls people unaffected by McArdle s The authors say circulating levels of several cytokines were significantly higher P 0 05 in patients than in controls The important parts of this sentence are in bold This can be translated as They measured the amount of cytokines in patients and controls and compared them using a statistical test Significantly means that the statistical test result showed that the levels were statistically different they appear to be real differences and are unlikely to occur by chance Higher obviously tells you that there were more cytokines than in controls P 0 05 is another part of the result of the statistical test A result that is P 0 01 P 0 05 or P 0 001 tells you that the statistical test showed that the differences unlikely to occur by chance Page 182 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

18 Glossary Most words are defined at the point when they are used in the Handbook Only scientific or medical words which are used repeatedly in the Handbook are defined below Adipose tissue Special cells in the body which store energy in the form of fatty acids Amino acids The building blocks of proteins Amino acid sequence Autosome Carrier The order of the amino acids in a protein Cell culture Chemokines Chromosome Codons Contractures Cytokines Double blind trial Double trouble Electrolytes Endoplasmic reticulum ER Enzyme Exons Fatty acid oxidation Frameshift mutations A chromosome which does not determine gender In this Handbook carrier is used to describe a person who has one copy of the PYGM gene without any mutations and one faulty copy of the PYGM gene which does have a mutation Carriers usually have approximately half the normal level of functional muscle glycogen phosphorylase Carriers do not usually have symptoms of McArdle disease In research papers carriers of McArdle disease are often described as heterozygotes Cells obtained from a person or animal for example cells obtained by a muscle biopsy from a McArdle person then grown in a research laboratory A sub group of cytokines which are small proteins produced by cells A structure within the cell which is basically a string of genes The mRNA is translated in triplets with each triplet being used to identify one amino acid These triplets are known as codons Severe muscle cramps Small proteins which are produced by almost all cells in the body Cytokines are used by the cells as a method to communicate A trial where neither the participant nor the researcher know which participants are receiving each treatment When two unrelated muscle diseases occur in the same person Several compounds including potassium sodium and calcium The body must maintain the correct amounts of these compounds in order to function properly A compartment within the cell involved in producing proteins basically the protein making factory A type of protein which has a special function of changing or breaking down one compound to another Muscle glycogen phosphorylase is an enzyme which breaks down glycogen into glucose 1 phosphate The coding regions of genes which are used to make messenger RNA mRNA The exons encode the sequence for making proteins A mechanism where fatty acids are broken down to release compounds which can be used to produce energy This provides the energy for the second wind in McArdle disease These are mutations which occur if nucleotides are added to or removed deleted from the gene This leads to the production of a protein which doesn t have the right sequence of amino acids and is not able to function in the normal way The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 183

Genotype The combination of versions of each gene that a person has Genotype phenotype relationship Glycogen storage disease GSD The relationship between which versions of each gene a person has and the physical effect of those genes on the body including severity of symptoms Hyperglycaemia A disease caused by a mutation which prevents the functioning of an enzyme normally required for the breakdown of glycogen into glucose Glycogen storage diseases result in intolerance to exercise and in general excluding GSD 0 result in storage of increased amounts of glycogen in the affected tissues or organs A process to convert glycogen into glucose This is the process which does not work in McArdle disease The breakdown of glucose to produce ATP The scientific medical term for someone who has two copies of the gene which are the same either two normal copies of the gene or two faulty copies of the gene Extremely high creatine kinase levels sometimes seen in McArdle people following muscle damage Excessive level of glucose in the blood Hyperkalemia Excessive level of potassium in the blood Hypertrophy Hypocalcemia Excessive development and bulking of the muscles Abnormally low levels of calcium in the blood Informed consent Innervation When participants agree to take part in a clinical trial having fully understood the risks and tests involved Culture of muscle cells in the same container as nerve cells Glycogenolysis Glycolysis Homozygote Hyper CK emia Introns Ketogenesis Malignant hyperthermia Non coding regions of genes which are not used to make messenger RNA The use of fatty acids as the main energy source to produce energy An inherited predisposition whereby some anaesthetic drugs produce an adverse reaction which includes an extreme rise in body temperature McArdle people may be more likely to have this reaction McArdle person In this Handbook McArdle person is used to mean a person who has received a definitive diagnosis of McArdle disease who has no functional muscle glycogen phosphorylase enzyme in their skeletal muscle cells Models of a Cells which have been made to mimic disease or animals that have a similar disease disease which can be used for research such as testing possible treatments Messenger RNA A temporary copy of the DNA sequence of the gene mRNA is made in the mRNA nucleus and then transported to the ER where it is used to produce a protein Muscle glycogen One of a group of enzymes which break down glycogen into glucose phosphorylase Myoglobinuria The presence of myoglobin in the urine Myoglobin is a protein which is released from damaged muscle Nonsense mediated decay Nucleotides A process which identifies and destroys mRNA which contains premature termination codons Chemical compounds which act as building blocks to make up DNA There are four nucleotides in DNA which are cytosine C thymine T guanine G and adenine A Pharmacological Particular chemicals which could bind to non functional enzymes to help them chaperones form the correct shape and become functional Phenotype The physical effect of genes on the body including on the severity of symptoms Page 184 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Placebo effect Premature stop codons Protein sequence Proteinuria Pyridoxal 5 phosphate PLP Rhabdomyolysis Ribosomes Second wind Sequencing Sex chromosomes Splice sites Statistically significant The citric acid cycle Unaffected by McArdle s A phenomenon where some people feel that their symptoms improve even if they are given a treatment with no active medicine for example a pill made of sugar or flour A mutation which has incorrectly introduced a stop codon too early in the DNA sequence It is also called a nonsense codon nonsense mutation or premature termination codon The order of the amino acids in a protein An excess of protein in the urine When mentioned in relation to McArdle disease proteinuria is generally used to describe myoglobin in the urine and is therefore used to mean the same as myoglobinuria In other circumstances for example in people unaffected by McArdle s proteinuria can also be used to describe the presence of other proteins A co factor special compound which is usually found bound to glycogen phosphorylase The vitamin B6 complex is a source of PLP Breakdown of muscle cells A component of the protein making factory ER which decodes the mRNA and joins amino acids together into a long chain to produce a protein Initially exercise depletes the free glucose in the muscle cells of McArdle people After a period of slower paced exercise or short rests other sources of energy become available to the muscle cells allowing McArdle people to continue to exercise A process of using special techniques and machinery to determine a genetic DNA sequence The X and Y chromosomes The number of these chromosomes which a person has will determine their gender The locations in the mRNA where exons are joined together after removal of the introns Where an experimental result for example the effect of a drug or treatment is unlikely to have occurred by chance Part of the mechanism to produce energy from food In this Handbook unaffected by McArdle s is used to describe a normal person who has no mutations in either copy of the PYGM gene People unaffected by McArdle s have two normal copies of the PYGM gene Online resources There is an on line medical dictionary at http www merriam webster com medlineplus The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 185

Page 186 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

A guide to the scienti ic and medical research into McArdle Disease explained in plain English This handbook explains in layman s terms the cause method of inheritance history and current and future treatments of McArdle disease also known as Glycogen Storage Disease Type V The handbook puts into plain English the published information about McArdle Disease which is normally written in technical language as it is aimed at medical or scienti ic professionals Some sections are necessarily still rather technical but in general the handbook should be understandable to those without any medical or scienti ic training It is fully referenced to the source publications The AGSD UK is grateful to the Vodafone Foundation s World of Difference programme which allowed the winner to prepare this handbook Old Hambledon Racecourse Sheardley Lane Droxford Southampton SO32 3QY Telephone 0300 123 2790 Registered charity no 1132271 Further copies of this book are available via www agsd org uk Ask about other languages v 1 1 1a AGSD UK Kathryn Birch Ph D is a scientist who has worked on McArdle Disease for four years She completed a Ph D creating cell models of McArdle disease During her studies she read most of the papers published on McArdle disease building an up to date knowledge of the historical and current scienti ic and medical research on the condition She has attended McArdle Clinics and AGSD UK Annual Conferences during which she has met dozens of people with McArdle disease and learned from their experiences Kathryn Elizabeth Birch Ph D Each chapter has an introduction which summarises the coming pages as simply as possible Then more detail is given in the chapter text using slightly more technical language The McArdle Disease Handbook The McArdle Disease Handbook The McArdle Disease Handbook A guide to the scienti ic and medical research into McArdle Disease explained in plain English Kathryn Elizabeth Birch Ph D

First published August 2011 Version 1 1 1 published August 2015 Published by Association for Glycogen Storage Disease UK Ltd Old Hambledon Racecourse Sheardley Lane Droxford Hants SO32 3QY Registered Charity number 1132271 Company limited by guarantee registered in England number 698112 www agsd org uk ISBN 978 0 9569658 1 3 Copyright Kathryn Birch 2011 2015 For personal use only not to be copied distributed or sold in any form without the prior permission of the author and publisher In case of discrepancies between the different language versions of the Handbook the English version is the original version and will prevail Disclaimer Unless otherwise stated this Handbook represents the views and opinions of the author Kathryn Birch and does not represent the views and opinions of AGSD UK or Vodafone World of Difference The purpose of this Handbook is to explain scientific research and knowledge about McArdle disease in layman s language so that it can be understood by people with McArdle disease or those interested in McArdle disease It is not intended to replace medical advice from your family doctor or specialist The information provided in this Handbook is correct to the best of the author s knowledge If you have any doubts about the accuracy of the information in this Handbook it is recommended that you read the original source full details in the reference list Where no definitive information is available the author has sought to suggest scientific rationale behind anecdotal observations reported by people with McArdle s It is stated where a theory or opinion of the author is given Due to the nature of scientific research current theories and understanding of the science behind McArdle s may change over time and subsequently be proven or disproven It is recommended that you check the AGSD UK website frequently to ensure you are reading the most up to date version of this Handbook Page 2 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Cover pictures Left People with McArdle disease can experience severe muscle damage which is indicated by raised creatine kinase levels There is a risk of kidney damage so hospitalisation may be required Stacey Reason and Dan Chambers have both experienced severe muscle damage with creatine kinase levels of over 200 000 IU L about a thousand times the normal level Right By working to regain their fitness creating a high aerobic capacity and learning helpful techniques like the use of walking poles as shown here Stacey Reason and Dan Chambers completed the 210 mile Walk over Wales in the summer of 2010 Some people with McArdle s cannot achieve these results and remain badly affected ongoing research is trying to find the answers Thanks to Stacey and Dan for permission to use their photos Centre McArdle disease is caused by an absence of muscle glycogen phosphorylase McArdle disease can be diagnosed by muscle biopsy A chemical reaction is carried out which produces a red purple colour if muscle glycogen phosphorylase enzyme is present Muscle biopsy photographs are reproduced by kind permission of Professor Caroline Sewry Great Ormond Street Hospital London and RJAH Orthopaedic Hospital Oswestry Centre top Normal muscle showing muscle glycogen phosphorylase enzyme Centre bottom Muscle of a person with McArdle disease showing absence of the enzyme Definitions of terms used in this Handbook In this Handbook McArdle person is used to mean a person who has received a definitive diagnosis of McArdle disease who has no functional muscle glycogen phosphorylase enzyme in their skeletal muscle cells McArdle people have two faulty copies of the PYGM gene In a McArdle person both copies of the PYGM gene contain a mutation which prevents functional muscle glycogen phosphorylase being made Unaffected by McArdle s is used in this Handbook to describe a normal person who has no mutations in either copy of the PYGM gene People unaffected by McArdle s have two normal copies of the PYGM gene Normal copies of the PYGM gene contain no mutations and can be used to make functional muscle glycogen phosphorylase People unaffected by McArdle s have a normal amount of functional muscle glycogen phosphorylase in their muscle cells Carrier is used to describe a person who has one normal copy of the PYGM gene without any mutations and one faulty copy of the PYGM gene which contains a mutation A carrier is likely to have approximately half the normal level of muscle glycogen phosphorylase Carriers do not usually have symptoms of McArdle disease Further definitions are given where appropriate throughout the Handbook There is also a glossary at the end of the Handbook for scientific or medical words used frequently in the Handbook which would not be included in a standard English glossary The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 3

Acknowledgements I would like to acknowledge Vodafone World of Difference UK charitable foundation for providing two months funding for this project I would like to thank the AGSD UK for supporting my application for funding Thanks especially to Andrew Wakelin AGSD UK McArdle Co ordinator for his comments on the draft version of the Handbook My Ph D project funded by AGSD UK and The Institute of Orthopaedics RJAH Orthopaedic Hospital Oswestry provided me with an opportunity to develop an interest in McArdle disease I would like to thank all the McArdle people who have shared their experiences with me and asked the most interesting and fundamental questions Thanks also to Mum Dad and Madelyn for their continued interest and encouragement and comments on the Handbook I am very grateful to my husband James Birch for his endless patience and support Funding for this project Kathryn Birch nee Wright submitted a proposal and successfully obtained funding from the Vodafone World of Difference charitable foundation under the World of Difference UK scheme This grant enabled AGSD UK to employ Kathryn Birch from January to March 2010 to write this Handbook Further writing was carried out by Kathryn Birch on an unpaid voluntary basis Kathryn Birch has no competing financial or academic interests Comments and feedback about this Handbook To contact the author please visit the AGSD UK web site at www agsd org uk and use the Contact Us page choosing McArdle Disease Handbook Page 4 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Contents Chapter Page 1 Introduction to McArdle disease 7 2 Symptoms and diagnosis of McArdle disease 13 3 The genetics of McArdle disease 33 4 Exercise muscle contractions and contractures muscle cramps 49 5 Muscle damage causes raised creatine kinase levels and myoglobinuria 59 6 Sources of energy in muscle cells 65 7 Dietary supplements which have been considered for McArdle s 85 8 The effect of age on the symptoms of McArdle disease 95 9 Differences in severity of symptoms between people 107 10 Mental and emotional aspects of McArdle disease 119 11 The effect of McArdle s on sexual activity pregnancy and birth 129 12 Medicines activities and other things which may be a greater risk for McArdle people 137 13 McArdle disease may increase the chances of having some diseases and conditions 143 14 McArdle s specialists and family doctors 151 15 Models of McArdle s can be used to test treatments 157 16 Potential therapies for McArdle disease 161 17 Details about this Handbook and the information in it 175 18 Glossary 183 19 References 187 20 Index 205 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 5

Visit the McArdle Disease pages on www agsd org uk for information and regular updates Page 6 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

1 Introduction to McArdle disease McArdle disease is caused by the lack of the muscle glycogen phosphorylase enzyme in muscle cells This enzyme is a special protein which plays a key role in changing glycogen into glucose in the muscle cells Glucose can then be used to provide energy to allow the muscle to contract and generate movement In McArdle people muscle glycogen phosphorylase does not function During exercise the muscle cells of McArdle people use up all their energy and are not able to generate further energy The short term lack of glucose causes tiredness and stiffness in muscles of McArdle people when they carry out exercise and can lead to muscle pain and muscle breakdown Without muscle glycogen phosphorylase the glycogen which is stored in the muscle cells cannot be changed into glucose The glycogen therefore accumulates in the muscle cells which is the reason why McArdle disease is known as a glycogen storage disease McArdle disease is named after Dr Brian McArdle a doctor who published the first medical paper describing his patient who had this muscle disease The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 7

1 1 A brief introduction to McArdle disease Muscle contractions are required to generate movement Muscle cells require a source of energy in order to perform muscle contractions Anaerobic exercise is a short burst of high intensity effort such as a sprint for a bus During anaerobic exercise glucose within muscle cells is broken down to produce ATP ATP is the source of energy for muscle cells The breakdown of glucose to produce ATP is called glycolysis However only a small amount of glucose is present in the muscle cells and this is used up within a few minutes of anaerobic exercise Muscle cells also contain much larger stores of glycogen Glycogen can be converted into glucose by a process called glycogenolysis In people unaffected by McArdle disease the process of converting glycogen into glucose requires several enzymes one of which is called muscle glycogen phosphorylase McArdle disease is caused by the lack of the muscle glycogen phosphorylase enzyme in muscle cells In McArdle people muscle glycogen phosphorylase is either absent or not functional The muscle cells are not able to convert the stored glycogen into glucose The muscle cells therefore run out of glucose and run out of energy The short term lack of glucose causes tiredness and stiffness in muscles of McArdle people when they carry out anaerobic exercise Rommel et al 2006 but this improves once exercise ceases McArdle people must rest until energy ATP is produced in the muscle cells by another method such as fatty acid oxidation or until glucose is obtained through the blood from the liver A period of rest is necessary because these other methods are slower to produce energy than glycogenolysis the method which normally involves muscle glycogen phosphorylase Once these other methods begin to replenish the amount of ATP in the muscle cells McArdle people can continue to exercise This is known as a second wind Amato 2003 However if McArdle people continue to exercise without rest the muscle cells use up all the available ATP and have no energy source available This can lead to breakdown of muscle cells rhabdomyolysis and muscle cramps fixed contractures both of which cause McArdle people to experience muscle pain Following rhabdomyolysis the components of the broken muscle cells are released into the bloodstream An enzyme normally found in muscle cells called creatine kinase CK also known as creatine phosphokinase CPK is released into the bloodstream following muscle damage A blood test performed by a family doctor or at a hospital can be used to measure the amount of CK in the blood which can be used as an indicator of the extent to which muscle damage has occurred The components of the broken muscle cells are transported through the bloodstream to the kidneys Myoglobin is another protein released from broken muscle cells Myoglobin is transported in the bloodstream to the kidneys where it is removed from the body in the urine resulting in dark red cola coloured urine known as myoglobinuria or proteinuria A rare but serious effect of extreme muscle damage is that broken muscle cells may block the filtration system of the kidneys preventing them working and resulting in kidney failure Martin et al 2001 DiMauro et al 2002 Quinlivan et al 2008 1 2 What is the cause of McArdle disease McArdle disease is caused by the absence of the muscle glycogen phosphorylase enzyme Mommaerts 1956 Schmid et al 1959 An enzyme is a protein which has a special function of Page 8 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

changing or breaking down one compound to another Muscle glycogen phosphorylase breaks down glycogen into glucose 1 phosphate A mutation in the PYGM gene which is responsible for muscle glycogen phosphorylase prevents the production of functional muscle glycogen phosphorylase 1 3 McArdle disease is one of the family of glycogen storage diseases There are many enzymes involved in the breakdown of glycogen into glucose If a mutation occurs in the enzyme which prevents it from functioning it will result in an inability to break down glycogen and its components to form glucose Diseases caused by a mutation in an enzyme required to break down glycogen are called glycogen storage diseases GSDs The glycogen storage diseases identified to date are listed in Table 1 1 There is further information about the glycogen storage diseases on the AGSD UK website http www agsd org uk The major symptom of every glycogen storage disease is an intolerance to exercise Glycogen storage is characteristic of all the diseases except GSD 0 Tarnopolsky et al 2006 described McArdle disease as the most common glycogen storage disease GSD VIII is caused by a mutation in phosphorylase b kinase Phosphorylase b kinase is essential for activation of the muscle glycogen phosphorylase enzyme However disease symptoms for GSD VIII are not very similar to McArdle disease possibly because there are difference mechanisms for activation of muscle glycogen phosphorylase in the absence of phosphorylase b kinase Orngreen et al 2009 1 4 Why is it called McArdle disease McArdle disease is named after Dr Brian McArdle the British family doctor who first published a paper describing a patient with the disease In 1951 Dr McArdle described a 30 year old male patient for whom light exercise caused pain in the muscles and continued exercise led to weakness and stiffness Pain during exercise would occur in any muscle in the body the most noticeable being in the arms or legs The pain would force the patient to stop and rest but it was noted that after a period of rest the patient was then able to exercise further Dr McArdle realised that after exercise the lactate lactic acid level of the patient did not increase as expected and that glycogenolysis was incomplete He also noticed that the patient s muscles were very weak even though they had quite a large bulk His astonishingly perceptive theory was that it is the enzyme system that is at fault it seems that the patient has a disorder of carbohydrate metabolism during exercise a change took place in the muscle chemistry which effectively led to a breakdown in glycogenolysis McArdle 1951 Mommaerts et al 1956 realised that McArdle disease was caused solely by the loss of muscle glycogen phosphorylase not the loss of any other related enzymes Schmid et al 1959 took samples of different skeletal muscles from a McArdle person muscles located between the back and shoulder middle of the back and the calf and found there was a lack of functional glycogen phosphorylase in all of these muscles He tested the different enzymes involved in the breakdown of glycogen and identified the cause of the disease as the loss of the ability to produce glucose 1 phosphate because muscle glycogen phosphorylase wasn t functional The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 9

y of the glycogen storage diseases identified to date Page 10 Kathryn Birch Debranching enzyme Andersen disease Branching enzyme Liver glycogen phosphorylase Phosphofructokinase Phosphorylase b kinase lack of one of the PHKA2 four subunits Glucose transporter GLUT2 Table 1 1 Summary of the glycogen storage diseases identified to date Fanconi Bickel syndrome G6PC G6PT1 AGL GBE1 PYGM PFK The McArdle Disease Handbook Version 1 1 1 The McArdle Disease Handbook Version 1 1 1 GYS2 Kathryn Birch Gene name Page 10 PFK Phosphorylase b kinase lack of one of the PHKA2 four subunits Glucose transporter GLUT2 Phosphofructokinase PYGL Liver glycogen phosphorylase GBE1 AGL PYGM Glucose 6 phosphate translocase Muscle glycogen phosphorylase Branching enzyme Debranching enzyme Glucose 6 phosphatase Phosphorylase b kinase deficiency Tarui disease Hers disease G6PT1 G6PC GYS2 Gene name Endoplasmic reticulum inorganic NPT I NPT II NPT III not fully phosphate transporter determined 1 4 glucosidase and 1 6 glucosidase GAA Glycogen synthase GSD XI Muscle glycogen phosphorylase McArdle disease Andersen disease Cori disease Pompe disease Deficient enzyme GSD IX Fanconi Bickel syndrome GSD VII Phosphorylase b kinase deficiency GSD VI and X Hers disease GSD V Cori disease Glucose 6 phosphate translocase Alternative name GSD IV Pompe disease Endoplasmic reticulum inorganic NPT I NPT II NPT II phosphate transporter determined 1 4 glucosidase and 1 6 glucosidase GAA Glucose 6 phosphatase Von Gierke disease GSD III McArdle disease GSD II GSD Ic Tarui disease GSD Ib Glycogen synthase Deficient enzyme Von Gierke disease Alternative name GSD Ia GSD 0 Glycogen Storage Disease e Disease PYGL

1 4 1 Other names for McArdle disease McArdle disease is also known as McArdle s McArdle syndrome McArdle s syndrome Muscle Phosphorylase Deficiency Myophosphorylase Deficiency Phosphorylase Deficiency McArdle Myopathy McArdle s Myopathy Muscle Glycogen Phosphorylase Deficiency and Glycogen Storage Disease GSD type V It may be called MacArdle s but this is incorrect because it is named after Dr Brian McArdle Myopathy is a general name for muscle disease 1 4 2 Other names and abbreviations for muscle glycogen phosphorylase Glycogen phosphorylase Phosphorylase muscle phosphorylase a and b myophosphorylase PYGM GP M MGP alpha 1 4 glucan orthophosphate glycosyltransferase or EC 2 4 1 1 1 5 How can I explain my McArdle disease to my friends and family who have never heard of it before This is my suggestion of how I would describe it to friends and family who haven t heard of McArdle disease before Your muscles use glucose to provide energy to move There isn t much glucose in your muscles so after a couple of minutes of vigorous anaerobic exercise the glucose is all used up There are also stores of glycogen in the muscle and there is an enzyme called muscle glycogen phosphorylase which normally changes the glycogen into glucose which gives the muscles more energy to continue to exercise In people with McArdle disease this enzyme doesn t work so the muscles run out of energy and can t get any more If the McArdle people continue to exercise the muscles basically starve and can be damaged However if the McArdle person rests for a short period the muscles can get energy from glucose in the blood or from other sources such as fat which is stored in the body The McArdle person can then continue to exercise 1 6 The future is promising for people with McArdle disease The future is positive for McArdle people In the 60 years since Brian McArdle published the first paper describing McArdle disease a lot of research into understanding McArdle s has been done as outlined in this Handbook There are research groups around the world carrying out research into McArdle s These range from research into brain functioning by Drs Quinlivan and Edelstyn in the UK to the investigations into exercise and diet by Drs Vissing and Haller in Denmark and the US to Prof Howell and colleagues carrying out research to increase the amount of a different form of glycogen phosphorylase the brain isoform using a drug called valproate in the McArdle sheep in Australia In the shorter term there are some excellent specialists who are highly knowledgeable about McArdle s and can offer up to date advice on diet and exercise for people with McArdle s The internet has also enabled people with McArdle disease to compare symptoms and advice and to provide support with others around the world through online patient support groups Research into improving everyday life with McArdle s is ongoing including investigating whether other genes phenotype modulators may have an effect upon the severity of symptoms In the longer term many different avenues for treatment are being considered including correcting the The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 11

expression of muscle glycogen phosphorylase which contains a mutation or replacing it with the brain glycogen phosphorylase enzyme Online resources There is information about McArdle disease and the other glycogen storage diseases on the AGSD UK website http www agsd org uk Page 12 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

2 Symptoms and diagnosis of McArdle disease The typical symptom of McArdle disease is pain caused by anaerobic exercise e g repetitive movements rapid movements or holding a pose The onset of pain occurs within a few minutes of exercise If the McArdle person does not stop and rest then prolonged exercise can cause painful cramps and red cola coloured urine may be seen a few hours later If a McArdle person interrupts exercise with short rests they then can get into a second wind which will then allow them to continue to exercise for longer The presence of a second wind is unique to McArdle disease so it can be used by a specialist as a clue to suggest a diagnosis of McArdle disease At present diagnosis is most commonly by muscle biopsy and or DNA testing A muscle biopsy is an invasive procedure but has the advantage that one sample can be used to test for many different muscle diseases DNA testing is usually targeted to a specific area of the DNA so is more appropriate if McArdle disease is already suspected DNA testing is highly accurate and becoming more commonly used DNA is usually obtained from a blood sample so is minimally invasive As McArdle disease is rare many McArdle people are misdiagnosed before they receive the correct diagnosis of McArdle disease Diseases which McArdle people are misdiagnosed with can include other muscle diseases diseases which cause inflammation of the muscles or chronic fatigue The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 13

2 1 The personal history of symptoms described by a typical McArdle person A typical McArdle person will have pain which occurs within a few minutes of anaerobic exercise They will remember these symptoms from childhood Often they will have struggled in sports lessons at school Children with McArdle s have great difficulty in carrying out activities such as cross country running if their teacher does not allow them to rest and get into a second wind Outside of school many McArdle children and adults will have developed coping mechanisms to allow themselves to rest without other people noticing These techniques could include frequently pretending to tie up their shoelace stopping to look in shop windows or pretending to use a mobile phone Some McArdle people will have discovered the second wind phenomenon they will have learnt that if they rest when they feel muscle pain they are then able to continue to exercise for a much longer period of time Some McArdle people will not have experienced the second wind phenomenon but all are able to experience it if taught Quinlivan and Vissing 2007 Most McArdle people will have experienced fixed contractures stiff contracted enlarged muscles often following more intense exercise Examples of exercise which is likely to lead to contractures includes intense activity such as running for the bus repetitive activity such as chewing or peeling potatoes or an activity where the muscles hold the body in one place for a long time such as squatting or some yoga positions Some McArdle people will have experienced dark red cola coloured urine which is particularly likely after a muscle contracture Some McArdle people will have attended a hospital emergency department because of the cola coloured urine and contractures In rare cases they may have had kidney failure and required dialysis McArdle people typically find that a very sedentary lifestyle makes it more of a struggle to perform any exercise They may find that if they keep fit they are able to do more However at the other extreme intense exercise can make the muscles very painful forcing the McArdle person to rest for many days while the muscles repair and recover After this period of time they may then find that exercise is harder and the muscles feel weaker than before For most McArdle people the symptoms remain similar throughout their life although some muscle weakness may occur as they get older The above description is a combination of information published by Quinlivan and Vissing 2007 Lucia et al 2008a and information from McArdle people provided to me via online discussion groups 2 1 1 Activities which McArdle people have reported can cause pain fatigue in muscles Here are some examples of activities which McArdle people have said can cause pain or fatigue in muscles activities are taken from published papers and from internet chat groups and e mail conversations This is a brief list designed to give some examples of the types of activities Page 14 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

Repetitive movements Holding a pose Rapid movements Repetitive movements Chewing McArdle 1951 Holding a opr ose Squatting crouching Chewing Using can McArdle opener 1951 Squatting oon r tciptoes rouching Standing Rapid movements Running Lucia et al 2008a such as running for the bus Running t al 2e008a such Climbing sLucia tairs eLucia t al 2008a as running for the bus Climbing stairs Lucia et al p2ausing 008a Very brisk walking without to rest Lucia et al 2008a Very brisk walking without pausing to rest fLucia et aa bl 2008a Cycling ast on ike Using can teeth opener Standing n tiptoes Brushing Lucia et Lifting a hoeavy weight such as al 2008a carrying a box bag Lucia Brushing teeth Lucia et Lifting 2008 a heavy weight such as al 2008a carrying a bpox bag Grating cheese or peeling Some yoga oses Lucia 2008 vegetables Grating heese or which peeling yoga oses Cycling fast published on a bike papers Table 2 1 cActivities causeSome muscle painpfor McArdle people Taken from references vegetables in brackets and personal communication with McArdle people unreferenced Table 2 1 Activities which cause muscle pain for McArdle people Taken from published papers references in brackets and personal communication with McArdle people unreferenced 2 2 Symptoms of McArdle disease The of McArdle are dwisease ell characterised and are summarised below Exceptions 2 2 symptoms Symptoms of Mdisease cArdle include some reported cases of late onset symptoms which are discussed further in section 8 1 3 The symptoms of McArdle disease are well characterised and are summarised below Exceptions Differences in severity of symptoms have been reported and possible explanations are discussed in include some reported cases of late onset symptoms which are discussed further in section 8 1 3 section 9 Differences in severity of symptoms have been reported and possible explanations are discussed in section 9 Very common symptoms of McArdle disease seen in almost all McArdle people Very symptoms of M isease seen in vaery lmost all M cArdle people common Exercise intolerance mcArdle uscles bdecoming tired quickly and running out of energy Lucia et al 2008a Exercise intolerance muscles becoming tired very quickly and running out of energy Lucia et al 2008a Continued exercise causing painful cramps contractures Lucia et al 2008a Continued exercise painful cramps contractures et a l 2008a Myoglobinuria dark causing red cola coloured urine after intense eLucia xercise Lucia et al 2008a say that the colour of urine due to myoglobinuria has been described by McArdle people as Myoglobinuria dark red cola coloured urine after intense exercise Lucia et al 2008a say looking like cola marsala or red wine that the colour of urine due to myoglobinuria has been described by McArdle people as looking plike miarsala red wine Muscle ain dcola uring ntense oer xercise will usually have existed since childhood Quinlivan and Vissing 2007 Muscle pain during intense exercise will usually have existed since childhood Quinlivan and Vissing w2ith 007 People McArdle s are able to experience a second wind if they exercise gently to warm up and rest when they feel pain they will then find that they can exercise for a much People with McArdle s are able to experience a second wind if they exercise gently to longer period It should be noted that a second wind is unique to McArdle disease Lucia warm up and rest when they feel pain they will then find that they can exercise for a much et al 2008a However some McArdle people do not know how to get into a second wind longer period It should be noted that a second wind is unique to McArdle disease Lucia or do not realise that this is occurring unless guided through it by a family doctor or et al 2008a However some McArdle people do not know how to get into a second wind specialist Quinlivan and Vissing 2007 or do not realise that this is occurring unless guided through it by a family doctor or specialist Quinlivan and Vissing 2007 High levels of creatine kinase CK in the blood at rest even when a McArdle person has not exercised intensely for hours or even days Lucia et al 2008a say that 100 of McArdle High levels of creatine kinase CK in the blood at rest even when a McArdle person has not people have average CK levels above 200U l and approximately 50 of McArdle people exercised intensely for hours or even days Lucia et al 2008a say that 100 of McArdle have average CK above 1000U l See section 5 3 2 for further information on creatine people have average CK levels above 200U l and approximately 50 of McArdle people kinase have average CK above 1000U l See section 5 3 2 for further information on creatine kinase The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 15 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 15

Occasional instances of very high levels creatine kinase CK in the blood Lucia et al 2008a define very high as being in the region of several thousand U l This is likely to be detected hours or days after the McArdle person has performed an intense exercise Less common symptoms of McArdle disease seen only in some McArdle people Some McArdle people have fixed proximal weakness Fixed proximal weakness is found in approximately 33 of people with McArdle disease Lucia et al 2008 It has not been possible to find a definition of fixed proximal weakness but I believe that in this context fixed means non reversible permanent and proximal is used to describe the muscles closest to the trunk of the body such as the shoulder and around the pelvis A feature rather than a symptom is the fact that some McArdle people find that they are able to exercise more easily if they have had a high sugar glucose drink or eaten carbohydrates such as pasta or rice prior to exercise Lucia et al 2008a Some of the more severe symptoms which can lead to diagnosis of McArdle disease 2 3 Kidney renal failure due to rhabdomyolysis and myoglobinuria can lead to hospital investigations which result in a diagnosis of McArdle s Biller 2007 Type of test Ischaemic non i Muscle pain myalgia inflammation myositis and damage caused by statins drugs taken exercise test to lower cholesterol can sometimes lead to hospital investigations which result in a diagnosis of McArdle disease Biller 2007 Cycle ergometer Diagnosis of McArdle disease exerci McArdle disease can be suspected based on a person having the symptoms described above or if Treadmill a sibling has already been diagnosed with McArdle disease There are several methods used to diagnose McArdle disease A brief description of each along Muscle biopsy s with the pros and cons and limitations is given in Table 2 2 They are not listed in any particular order An indication of how commonly I believe each method is used to diagnose McArdle s is also Muscle biopsy e given DNA genetic tes Creatine Kinase Electromyogram Magnetic resona 31P MRS Table 2 2 Method and relevant notes Page 16 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

ds to diagnose McArdle disease An overview of my opinion of how commonly each method is used whether it produces a defin s m EMG Sometimes used ance spectroscopy Rarely used enzyme activity test Rarely used Recently become one of the most common methods Very commonly used Sometimes used ise test Rarely used The McArdle Disease Handbook Version 1 1 1 Very commonly used Creatine Kinase blood test Yes No No No Principally used by scientists investigati which occur in the muscle cells during e Requires complex and expensive equipm Used predominantly in the UK McArdle Kathryn Birch No No Use of this test was first described by D and has been in use for about 50 years Principally used by scientists investigating changes which occur in the muscle cells during exercise Requires complex and expensive equipment High success rate at producing a definitive diagnosis Not very invasive Can be prohibitively expensive but likely to become cheaper in the future CK is invariably raised in McArdle disease so this simple blood test is a useful first sign that something needs investigating Not diagnostic and relevant notes Page 17 The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 17 Table 2 2 Methods to diagnose McArdle disease An overview of my opinion of how commonly each method is used whether it produces a definitive diagnosis Rarely used High success rate at producing a definit Not very invasive Can be prohibitively likely to become cheaper in the future CK is invariably raised in McArdle diseas blood test is a useful first sign that som investigating Not diagnostic Magnetic resonance spectroscopy 31P MRS Looks for lack of enzyme and excess of success rate at producing a definitive d invasive method of diagnosis High risk of inaccurate result Requires biopsy Often used by scientists in the Sometimes used No Yes Probably not Yes Recently become one of the most common methods Often used by scientists testing the effe or diet No Electromyogram EMG Looks for lack of enzyme and excess of glycogen High success rate at producing a definitive diagnosis Most invasive method of diagnosis High risk of inaccurate result Requires invasive muscle biopsy Often used by scientists in the past Used predominantly in the UK McArdle s clinic Often used by scientists testing the effects of exercise or diet Use of this test was first described by Dr Brian McArdle and has been in use for about 50 years Notes Notes Probably not Yes No No No Will a positive result definitively diagnose McArdle s No DNA genetic testing Very commonly used Muscle biopsy enzyme activity test Rarely used r exercise test Very commonly used Rarely used Sometimes used Very commonly used Very commonly used Will a positive result definitively diagnose McArdle s No ischaemic forearm Muscle biopsy staining of slides Treadmill exercise test Cycle ergometer exercise test staining of slides How often is this test used to diagnose McArdle s blood test Ischaemic non ischaemic forearm exercise test Type of test sting How often is this test used to diagnose McArdle s

2 3 1 Exercise test There are three types of exercise test a forearm test a cycling test or a treadmill All three are intended to test whether the body is able to break down glycogen to produce glucose in order to provide the muscles with energy during exercise What is tested When a muscle of an unaffected person is exercised vigorously anaerobic exercise the free glucose is rapidly used up Stored glycogen is then broken down by the process of glycogenolysis to produce energy During glycogenolysis lactate and pyruvate are produced In people unaffected by McArdle s the amount of lactate lactic acid and pyruvate should increase 5 6 fold Dubowitz et al 2007 Glycogenolysis is required to produce the rise in lactate and pyruvate levels In McArdle people the absence of functional muscle glycogen phosphorylase blocks glycogenolysis McArdle people therefore do not have the expected increase in lactate and pyruvate levels In the ischaemic forearm test a cuff is used to reduce blood flow to the arm Ischaemic means to reduce blood flow It is performed as an ischaemic test to prevent the blood bringing glucose or fatty acids to the muscle This ensures that anaerobic not aerobic exercise occurs However recent studies have shown that similar results with less risk of muscle damage can be achieved with a non ischaemic forearm test Niepel 2004 Cons of all exercise tests The level of effort must be below the maximum so that severe complications like rhabdomyolysis and myoglobinuria do not occur Fernandes 2006 Following exercise increased ammonia levels increased uric acid levels see section 13 1 for the relationship between uric acid levels and gout and increased creatine kinase are often seen Milunksky 2010 Limitations The exercise tests do not definitively diagnose McArdle disease An a bsence of increase in lactate and pyruvate levels indicates a metabolic disease caused by a block in glycogenolysis Many other glycogen storage diseases prevent lactate production after anaerobic exercise Lane 1996 The exercise test does not distinguish whether the person has McArdle disease or another other metabolic disease for example another glycogen storage disease such as Tarui disease phosphofructokinase deficiency Abramsky 2001 Cori disease and Tarui disease can produce flat not increasing lactate levels after the forearm test Biller 2007 If a small increase in lactate 1 5 3 fold of resting levels and a very high increase in ammonia occurs it may suggest that the person has a disease where a small amount of enzyme is still functional examples of these diseases would be phosphoglycerate mutase phosphoglycerate kinase and lactate dehydrogenase deficiencies Abramsky 2001 A different disease called myoadenylate deaminase deficiency MADD is another metabolic disease characterised by decreased ammonia production Lane 1996 MADD is discussed further in section 9 3 2 If a person with MADD exercises the amount of lactate will increase and the amount of ammonia will be lower than expected Lane 1996 Abramsky 2001 For this reason the level of ammonia in the blood plasma ammonia is usually measured before and after an ischaemic forearm test Lane 1996 Page 18 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

2 3 1 1 Ischaemic or non ischaemic forearm exercise test How the ischaemic forearm test is carried out A pre test blood sample is taken before the test A cuff tight band is put around the forearm or occasionally the thigh The forearm is contracted by squeezing a ball or balloon or the thigh is contracted at maximum force strength for one minute or until extreme pain The cuff is then loosened Blood samples are taken for example at 1 3 5 and 10 minutes after exercise The blood is analysed to determine whether the expected increase in lactate and pyruvate occurs After exercise the amount of lactate in the blood will not increase Cush 2005 in McArdle people but McArdle people will have an increase in ammonia levels in the blood which can go up to 360 560 g dl Lane 1996 It is important that ammonia levels in the blood rise as this shows that the person has exercised enough as an incorrect result could be obtained if the person who is being tested does not exercise with enough effort Lane 1996 Cons of the ischaemic forearm test The test can lead to muscle damage Cramping muscle pain and contracture of the muscle may occur following the test Cush 2005 There is a small risk of the severe problem of compartment syndrome discussed further in section 12 3 2 The risk of compartment syndrome is much lower if the non ischaemic forearm test is performed There is also a risk of the test causing severe muscle damage which could lead to kidney failure see section 5 for further information on rhabdomyolysis and kidney failure Meinck et al 1982 published a report where a 57 year old McArdle person was asked to perform an ischaemic forearm test The muscle of the tested forearm was damaged which resulted in myoglobinuria and raised creatine kinase levels in the blood The person was placed under medical observation and instructed to drink plenty of fluids Although kidney failure did not occur the authors Meinck et al 1982 warned that it could be a potential hazardous side effect of the ischaemic forearm test How the non ischaemic forearm test is carried out A non ischaemic forearm test similar to that described above but without use of a cuff is now recommended A study by Kazemi et al 2002 found that the non ischaemic forearm test was able to distinguish McArdle people from unaffected people The non ischaemic forearm test is much less likely to cause damage Niepel 2004 The ischaemic forearm test can cause a lot of pain and discomfort for McArdle people whereas the non ischaemic test produces almost no discomfort Abramsky 2001 Cons of the non ischaemic forearm test I think that it seems possible that muscle damage could also be a side effect of the non ischaemic forearm test if the person exercises too vigorously as described by Meinck et al 1982 for the ischaemic forearm test Pros of both the ischaemic and non ischaemic forearm exercise tests It is not very invasive the only invasive part is taking blood samples It can be performed with relatively simple equipment Cons of both the ischaemic and non ischaemic forearm exercise tests If people who don t have McArdle s are very weak or are unmotivated during the exercise test no increase in lactate and pyruvate may be seen resulting in an incorrect diagnosis of McArdle disease Lucia et al 2008a It may produce a positive result in people with other similar diseases which affect glycogenolysis or glycolysis like some of the other glycogen storage disease The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 19

Only works for children old enough to squeeze the ball balloon It was suggested by Lane 1996 that false negative results could be seen in the rare cases of McArdle people with low levels of functional muscle glycogen phosphorylase but no experimental data was provided to support this theory If both lactate and ammonia increase only a small amount it suggests that either the person being tested did not put enough effort into the exercise or that the wrong vein was used to sample the blood The correct vein to use is called the median cubital vein and one example of an incorrect vein to use is the basilica vein Abramsky 2001 The blood samples must be assayed quickly so it is essential that the test is performed at a location near to a biochemistry laboratory Barnes 2003 2 3 1 2 Cycle ergometer exercise test A cycle ergometer is a static bike commonly found in a gym Pedalling turns a wheel which runs over a band The band can be tightened to provide more resistance making it harder work to pedal and increasing the amount of energy the person needs to move the pedals energy is measured as Watts W What is tested This test measures whether exercise leads to an increase in lactate and pyruvate in the blood In addition breathing apparatus is often used to quantify the amount of oxygen used for exercise VO2max How the cycle ergometer test is carried out McArdle people have very low work capacities so the cycle ergometer should be precisely adjusted to provide a low amount of resistance 0 50W The person begins to pedal gently with the amount of resistance being increased by 5 10W every other minute The person being tested wears a type of oxygen mask over their head This allows measurement of the amount of oxygen they breathe in oxygen consumption called VO2 and the amount of carbon dioxide breathed out called VCO2 These two numbers can be combined to produce a VCO2 VO2 ratio A heart rate monitor can be used to measure heart rate A blood sample is taken prior to exercise and after exercise to find out the lactate levels in the blood Abramsky 2001 If the blood lactate levels do not rise it may suggest a diagnosis of McArdle s or Tarui disease To determine which of these diseases a person has the person is asked to briefly exercise at maximum capacity which is called VO2max The person is then asked to exercise at approximately 40 of VO2max Abramsky 2001 In McArdle people this level of exercise causes a high heart rate and a high level of perceived exhaustion it feels like really hard work to pedal until 8 10minutes into the exercise when the second wind occurs At this point 8 10mins into exercise McArdle people have a dramatic drop in heart rate and it feels much easier to exercise pedal even though they are pedalling at the same rate as before It can be further tested by increasing the resistance making the band tighter so that the person has to pedal even harder This causes the persons heart rate to increase In some experiments the person is then given intravenous glucose glucose via a needle and drip in the arm 50ml of a 50 solution In McArdle people the glucose leads to a second second wind the heart rate will drop again and it will feel easier to pedal again Page 20 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

These changes in heart rate and second wind are diagnostic of McArdle disease In Tarui disease a second wind does not occur and intravenous glucose makes it harder for the person to exercise Abramsky 2001 To ensure that the person exercised is not working at their maximum level their pulse rate should be kept below 150 beats min for adults and 150 180 beats min for children Fernandes 2006 Pros of cycle ergometer for exercise tests pros are not specific to testing for McArdle disease Keeps person being tested in the same place so it is easy for them to wear a facemask which is used to monitor the amount of oxygen being breathed in and amount of carbon dioxide being breathed out It is also easier to take blood from the person as they are staying in the same place It is easy to use the cycle machine to accurately quantify the amount of exercise the person is doing adapted from Cooper and Storer 2001 For these reasons a cycle ergometer is often used by scientists testing the effect of diet or exercise on the ability of McArdle people to exercise for example Drs Haller and Vissing frequently publish papers using cycle ergometers e g Vissing et al 2009 Cons of cycle ergometer for exercise tests cons are not specific to testing for McArdle disease If people do not cycle regularly it may feel strange and may result in premature leg tiredness if it is an unfamiliar form of exercise adapted from Cooper and Storer 2001 Children have to be old enough to be able to cycle 2 3 1 3 Treadmill test How the test works This is similar to the ischaemic non ischaemic forearm tests and also similar to the cycle ergometer test What is tested The treadmill test is used to measure presence of second wind effect of exercise on heart rate and to test whether exercise leads to muscle pain Breathing apparatus can be used to measure the amount of oxygen breathed in and carbon dioxide breathed out used to calculate VO2 max Perez et al 2009 How the treadmill test is carried out The person being tested walks on a treadmill The speed of the belt and the slope of the belt level of inclination can be adapted so that the person is walking at a speed of 3 5km h with a pulse rate of 150 180beats min The length of time that it takes for the person to become exhausted can indicate which disease they may have Glycogen storage diseases will make people exhausted more rapidly whereas diseases caused by defects in fatty acid oxidation will make people feel exhausted later Fernandes 2006 Pros of the treadmill test It can be used to test very young children as soon as they can walk Fernandes 2006 Perez et al 2009 Everyone is used to walking around so it is a very natural and familiar way to test Cooper and Storer 2001 Cons of the treadmill test It can be harder to measure oxygen and carbon dioxide It is perhaps harder to obtain blood samples Note At the UK McArdle s Clinic the treadmill test was sometimes used by experienced physiotherapists to teach McArdle people how to achieve a second wind if they had not previously experienced second wind before personal observation at the clinic while located at the RJAH Orthopaedic Hospital in Oswestry UK The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 21

2 3 2 Muscle biopsy What is tested A muscle biopsy can be used to test for two things 1 An accumulation of glycogen McArdle people and people with other glycogen storage diseases apart from GSD 0 have an accumulation of glycogen within the muscle cells Unaffected people have a much lower amount of glycogen in their muscle cells 2 An absence of functional muscle glycogen phosphorylase in the muscle cells Unaffected people have a high level of muscle glycogen phosphorylase in their muscle cells How is the muscle biopsy test carried out The McArdle person is placed under either local or general anaesthetic A surgeon removes a piece of muscle from one of the large muscles such as the upper arm thigh or calf The piece of muscle is sent to a histology department who will preserve it if necessary and carry out the necessary tests To confirm the validity of the test the enzyme must be seen in either an internal control a blood vessel or an external control muscle tissue from someone who is known not to have any muscle disease The family doctor or specialist should then be sent a report from the histology department outlining the results It should be noted that muscle biopsies can either be taken as a needle biopsy a hollow needle is used to cut and remove a sample of the muscle or as an open biopsy a surgeon cuts and removes a small sample of muscle A needle biopsy is normally smaller than an open biopsy is likely to cause less damage to the muscle and have a quicker healing time A needle biopsy is recommended by Dubowitz and Sewry Heckmatt et al 1984 Dubowitz et al 2007 Some textbooks recommended that a muscle biopsy be performed in the most symptomatic area Cush 2005 However in theory I think that it shouldn t matter which muscle the biopsy is taken from because if a person has McArdle s muscle glycogen phosphorylase is missing not functional in all the skeletal muscles of the body Surgeons usually chose to biopsy the thigh calf or bicep because they are large muscles so it is easier to take a small biopsy without damaging any surrounding tissue Cons of the muscle biopsy test Malignant hyperthermia is an inherited condition whereby some anaesthetic drugs produce an adverse reaction which includes an extreme rise in body temperature see section 12 3 1 McArdle people are at an increased risk of having malignant hyperthermia like symptoms which can cause a dangerous reaction to general anaesthetic It is important to remind inform your surgeon of this risk prior to surgery Dubowitz and Sewry 2007 recommend muscle biopsy be performed under local anaesthetic which reduces risk of side effects like malignant hyperthermia Limitations An inaccurate result may be obtained if muscle biopsy is performed shortly after a period of rhabdomyolysis and muscle damage If muscle damage has occurred prior to the biopsy being taken small immature regenerating muscle fibres may be seen which are positive for the phosphorylase stain due to expression of other isoforms of glycogen phosphorylase enzyme Lane 1996 An explanation of the other isoforms of glycogen phosphorylase is given in section 6 5 Serial sections pieces of tissue cut from the same muscle biopsy sample can be stained with antibodies for other immature proteins such as myosin which will confirm that these fibres are Page 22 Kathryn Birch The McArdle Disease Handbook Version 1 1 1

immature Dubowitz et al 2007 It is not possible to distinguish between the different isoforms of glycogen phosphorylase enzyme in the phosphorylase staining test Testing a muscle biopsy shortly after rhabdomyolysis has occurred is likely to result in a false negative result a person who really does have McArdle disease will be told that there is nothing wrong with them Notes It should be noted that McArdle disease cannot be diagnosed by skin biopsy This is because McArdle disease only affects skeletal muscle cells Skin cells have a different form of glycogen phosphorylase It would be advisable to ask request that the muscle biopsy is stored by the laboratory carrying out the tests in liquid nitrogen or a 80 freezer as appropriate until the diagnosis is confirmed If there are any questions or uncertainty about the diagnosis the stored muscle biopsy can be used to perform further tests This eliminates the need for a further biopsy 2 3 2 1 Staining of slides with slices of muscle What is tested Following a muscle biopsy thin slices of muscle are made and mounted onto thin glass slides The muscle fibres can be stained to determine the amount of glycogen present A special stain called the periodic acid Schiff PAS stain DiMauro et al 2002 Dubowitz et al 2007 is used to stain glycogen A chemical reaction is carried out to determine whether there is functional muscle glycogen phosphorylase in the muscle fibres Amato 2003 Muscle glycogen phosphorylase is used to produce a compound which can be stained to produce the purple brown colour If the muscle glycogen phosphorylase is not functional it will not produce this compound and no colour will be seen After staining the slides with slices of muscle will be examined under a microscope It is important that the laboratory carrying out these tests performs the same tests on a biopsy from an unaffected person a negative control at the same time This removes the possibility of a false negative test if some part of the test does not work correctly Pros of the staining of slides with slices of muscle test If the phosphorylase staining is carried out correctly it will provide an accurate and specific diagnosis of McArdle disease An absence of muscle glycogen phosphorylase is diagnostic of McArdle disease It will work whether the mutation is known or a brand new mutation which has not been identified before One muscle biopsy can also be used to test for and exclude many different muscle diseases Cons of the staining of slides with slices of muscle test It should be noted that an accumulation of glycogen will be seen from almost all the glycogen storage diseases and therefore is not diagnostic of McArdle disease The site of the biopsy may be painful until healed and may cause a scar It is more invasive than any of the other tests 2 3 2 2 Enzyme activity test How is an enzyme activity test carried out It is also possible that the amount of functional muscle glycogen phosphorylase in muscle biopsy sample can be tested in a different way A biopsy sample is taken as described below Instead of making thin slices the sample is homogenised mashed up The McArdle Disease Handbook Version 1 1 1 Kathryn Birch Page 23