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Birth Defect Brochure

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Phenylketonuria (PKU) 


 Phenylketonuria (commonly known as PKU) is an inherited disorder that increases the levels of a substance phenylalanine in the blood. Phenylalanine is a building block of proteins (an amino acid) that is obtained through the diet. It is found in all proteins and in some artificial sweetners. If PKU is not treated, phenylalanine can build up to harmful levels in the body, causing intellectual disability and other serious health problems.



What Is PKU?

PKU is caused by a genetic mutation (change in DNA) in the human phenylalanine hydroxylase (PAH) gene. There are many different types of of mutations that can affect the PAH enzyme. Enzymes are proteins that speed up and control chemical reactions. Lack of the PAH enzyme means that a chemical called phenylalanine, which is found in some foods, can't be processed properly by the body.


The signs and symptoms of PKU vary from mild to severe. The most severe form of this disorder known as classic PKU. Infants with classic PKU appear normal until they are a few months old. Without treatment, these children develope permanent intellectual disablilty. Seizures, delayed developement, behavioral problems, and psychiatric disorders are also common. Untreated individuals may have a musty or mouse-like odor as a side effectof excess phenylalanine in the body. Children with classic PKU tend to have lighter skin and hair than uneffected family members and are also likely to have skin disorders such as eczema.


What Are Symptoms and Causes?

How do we detect PKU? And How We Can Treat It?

Genetic testing can be done on a blood sample. Genetic testing, also called DNA testing, looks for changes in the pair of genens that causes PKU.

Prompt treatment is needed to prevent intellectual disabilities. Newborns need to drink a special medical formula. Ir is still possible to breastfeed your baby as long as you get help from your dietician. Babies who are breastfed usually need the medical formula as well. Most children need to eat a special diet made up of very low-protein. The medical formula gives babies and children with PKU the nutrients and proteins they need while helping their Phe levels within a safe range. Children must avoid :

all dairy products

regular formula

meat and poultry



nuts and peanut butter

dried beans

regular flour

aspartame (quickly raises blood levels of Phe and contains high amount of Phe)

Dr. Dorothy Katherine Grange, MD:

Dr. Grange is the Director of St. Louis Children's Down Syndrome Center. She specializes in medical genetics, inherited disorders, phenylketonuria (PKU), birth defects, malfunction syndromes, chromosomal disorders, metabolic disorders, Marfan syndrome, connective tissue, overgrowth disorders, craniofacial disorders and pediactric pathology. You must have a referral from your primary care physician before you make an appointment with Dr. Grange.


1 Childrens Pl, St. Louis, Mo 63110


Who Should You Contact?

Where is St.Louis Children's Down Syndrome Center?

Who should you contact?

The PKU Foundation

Contact: 214-446-4003

Unified to Support Metabolic Disorders

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