Phenylketonuria (PKU): Screening and the Low-Protein Diet

What it is

Phenylketonuria (PKU) is an inherited disorder of amino acid metabolism. People with PKU can't process phenylalanine (Phe), an amino acid — a building block of proteins — found in almost all foods.

Why it matters

If Phe builds up too high, it can damage the brain and cause severe intellectual disability.

Finding it early

Every baby born in a U.S. hospital must now be screened for PKU, which makes it easier to diagnose and treat early.

Treatment: a special diet

The best treatment is a diet of low-protein foods:

• Newborns: special formulas.
• Older children and adults: many fruits and vegetables, plus some low-protein breads, pastas and cereals.
• Nutritional formulas supply the vitamins and minerals the diet can't.

Outlook

Babies who start the diet soon after birth develop normally, and many have no symptoms. It's important to stay on the diet for life.

Sources

Based on the MedlinePlus health topic "Phenylketonuria," National Library of Medicine, drawing on the National Institute of Child Health and Human Development; a work of the United States government in the public domain.