Overview
Diagnosis
Newborn screening identifies almost all cases of phenylketonuria (PKU). In the United States, all 50 states require newborns to be screened for PKU, and many other countries routinely screen infants as well.
If you have PKU or a family history of it, your healthcare provider may recommend screening tests before pregnancy or birth. Blood tests can also identify PKU carriers.
Testing your baby after birth involves:
• Collecting a few drops of blood from your baby’s heel, usually after 24 hours of birth and after the baby has had some protein in the diet.
• Laboratory testing of the blood sample for metabolic disorders, including PKU.
• Additional tests if initial results suggest PKU, including more blood and urine tests, and possibly genetic testing to identify gene changes associated with PKU.
Treatment
Early and lifelong treatment can prevent intellectual disability and serious health problems.
The main treatments for PKU include:
• Following a lifetime diet with very limited intake of foods containing phenylalanine.
• Taking a PKU formula — a special nutritional supplement — to ensure adequate protein and essential nutrients without phenylalanine.
• Medications for certain individuals with PKU.
A safe phenylalanine intake varies for each person and can change over time. Healthcare providers determine safe amounts through:
• Regular review of food records and growth charts.
• Frequent blood tests to monitor phenylalanine levels, especially during growth periods and pregnancy.
• Other tests assessing growth, development, and overall health.
A registered dietitian can help manage the PKU diet, make adjustments, and suggest strategies for adhering to dietary restrictions.
Foods and products to avoid include:
• High-protein foods such as milk, eggs, cheese, nuts, soy products, beans, poultry, beef, pork, fish, and certain grains and vegetables.
• Drinks and foods containing aspartame.
• Some medications, vitamins, and supplements that contain phenylalanine or amino acids.
PKU formula
Special phenylalanine-free formulas provide essential protein and nutrients safely:
• Infants and toddlers need a phenylalanine-free formula instead of regular formula or breast milk, with careful calculation of any added breast milk or formula.
• Older children and adults continue with a phenylalanine-free nutritional supplement divided across meals and snacks.
PKU medication
Medications may complement the PKU diet:
• Sapropterin (Kuvan) can be used with or sometimes instead of the PKU diet for some individuals.
• Pegvaliase-pqpz (Palynziq) is an enzyme therapy for adults when diet and other treatments do not sufficiently lower phenylalanine levels. It is available under a restricted program due to potential side effects.
Consistent adherence to dietary restrictions, supplementation, and medication when indicated is essential to prevent the serious complications of PKU and support lifelong health.
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