Phenylketonuria, Pediatric
Phenylketonuria (PKU) is a disease that is caused by a lack of the liver enzyme that is needed to digest phenylalanine. Phenylalanine is an amino acid. It is most commonly found in foods that contain protein, such as meat, cow's milk, over-the-counter infant formula, and breast milk.
What are the causes?
PKU develops when the gene for making the enzyme needed to digest phenylalanine is changed (mutated). To have the disease, a child must inherit a mutated gene from each parent.
What increases the risk?
A child is more likely to develop this condition if both parents have the mutated gene that causes PKU. This condition is most common in those of European and Native American descent.
What are the signs or symptoms?
Signs or symptoms of this condition usually do not begin to show until after the first few weeks of life. Symptoms may include:
Vomiting.
Red, scaly rash.
Intellectual disability.
Seizures.
Tremors.
Stiffness.
Irritability.
Unpleasant, musty smell.
Small head.
Short height.
How is this diagnosed?
PKU is diagnosed with a blood test. If the test is positive, additional blood, urine, or genetic tests may be run to verify the results. All newborns should have this test within 1 to 2 days of birth.
How is this treated?
PKU is treated by removing phenylalanine from the diet. Babies with the condition must immediately be put on a phenylalanine-free formula. Older children should eat a low-protein, mainly vegetarian, diet. They will need to:
Limit how much starchy foods they eat. These foods include bread, corn, potatoes, pasta, rice, and beans.
- Completely avoid:
High-protein foods, such as milk, meat, chicken, eggs, nuts, and fish.
- Foods, drinks, and medicines that contain aspartame, a low-calorie sweetener. This is commonly found in:
Diet soda.
"Sugar-free" foods, such as spreads and ice cream, yogurt, and pudding.
Some children's chewable medicines.
It is important to read all food labels completely before giving your child a new food. Your child will not outgrow PKU. It is very important that this diet is followed very closely throughout your child's life. The long-term effects of high levels of phenylalanine in the blood can be very serious.
Follow these instructions at home:
- Make sure your child follows diet instructions as told by your health care provider.
Do not let your child eat or drink any products containing aspartame.
Do not let your child eat high-protein foods.
Limit how much starchy foods your child eats.
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Give your child any dietary supplements only as told by your child's health care provider. Do not give your child any other vitamins or dietary supplements without the approval of your child's health care provider.
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Keep all follow-up visits. This is important.
Contact a health care provider if:
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Your child has a seizure.
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Your child vomits repeatedly.
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These symptoms may represent a serious problem that is an emergency. Do not wait to see if the symptoms will go away. Get medical help right away. Call your local emergency services (911 in the U.S.). Do not drive yourself to the hospital.
Summary
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Phenylketonuria (PKU) is a disease that is caused by a lack of the liver enzyme needed to digest the amino acid phenylalanine.
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Phenylalanine is most commonly found in foods that contain protein, such as meat, cow's milk, over-the-counter infant formula, and breast milk.
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PKU is treated by removing phenylalanine from the diet.
This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.
