Phenylketonuria (PKU) is a genetic disorder in which the body can't process part of a protein called phenylalanine (Phe). Phe is in almost all foods. If the Phe level gets too high, it can damage the brain and cause severe mental retardation. Today, all babies born in US hospitals must be screened for PKU. (This makes it easier for pediatricians to diagnose and treat the problem early.)
There are special formulas for newborns with PKU. Older children and adults should focus on a diet composed of many fruits, vegetables, and some low-protein breads, pastas, and cereals. There are several nutritional formulas which provide the vitamins and minerals people with PKU are missing.
Babies who get on this special diet soon after they are born develop normally. And although many of them won't have symptoms of PKU, it is important that they stay on the diet for the rest of their lives.