Phenylketonuria (PKU) in Children | Diagnosis & Treatments

How we diagnose phenylketonuriais

Newborn screening for PKU is required in all 50 states. This is because treatment needs to begin within the first weeks of life in order for the child to live a full life. A baby that tests positive for PKU by newborn screening may be referred to Boston Children’s by their primary care doctor. At the hospital, blood and urine tests will be conducted to determine the exact type of PKU and the treatment needed.

Newborn screening

  • It is the first level of testing.
  • New England Newborn Screening Program screens all babies in New England
  • Testing occurs within two days after birth.
  • High phenylalanine with low tyrosine levels indicates PKU.
  • Babies testing positive for PKU have their results sent to a physician who refers the baby to Boston Children’s, or a hospital like Boston Children’s, for confirmation.

Metabolic disorder blood test

  • It’s used to confirm the newborn screening test results.
  • It’s conducted by the Metabolism Program at Boston Children’s.
  • A needle is used to draw blood from the baby’s arm.
  • Test is done within the first week after birth, or earlier.
  • Analyzes the levels of amino acids, including phenylalanine and tyrosine.
  • High levels of phenylalanine indicate PKU.
  • A urine specimen is collected by applying a special collection bag to the baby’s bottom.

How we treat phenylketonuriais

The main treatment for phenylketonuriais is avoiding foods with high protein and taking special medical formula as prescribed. People with PKU should follow a low-phenylalanine diet for the rest of their lives, even if symptoms do not surface. Foods high in phenylalanine include foods such as:

  • beef
  • fish
  • chicken
  • eggs
  • milk
  • chocolate
  • cheese
  • beans
  • nuts
  • peas
  • soybeans
  • diet sodas
  • the artificial sweetener aspartame contains phenylalanine

Individuals with PKU often are allowed these foods in their diets in moderation:

  • cereals
  • breads
  • pastas
  • rice
  • fruits
  • vegetables
  • milk substitutes

Those with PKU must also take:

  • Phenylalanine-free baby formula or continuation of breast feeding supplemented with special formula.
  • Special medical formula for children and adults which contains either free amino acids but not phenylalanine or glycomacropeptide which has very little phenylalanine

If your child has also been given a trial of the PAH co-factor medication known as sapropterin (Kuvan) and found to be responsive, he or she may also be on this drug.

Coping and support

PKU is a uniquely challenging disease, which requires your child to stay disciplined and follow the diet every day, for the rest of his life. Our team of nurses and nutritionists can help you come up with strategies to help your child be able to comply with the diet, and our psychologists can help your child cope with the daily stress of managing his diet. The diet is expensive but is usually covered by health insurance or public health programs. Our social workers will help you understand what financial support you're entitled from your private insurer, the Public Health Department, or Medicaid. Learn more about the patient and family resources available at Boston Children's.