Definition

An inherited disorder that causes a build-up of a substance called phenylalanine in the blood and other body fluids. Phenylalanine is an amino acid (a building block of proteins), so certain foods, such as meat, eggs, nuts, and milk, contain high levels. Some artificial sweeteners, such as aspartame, also contain high levels of phenylalanine. The signs and symptoms of PKU can be mild or severe and may include light skin and hair, skin rashes, seizures, developmental delays, and movement, behavioral, and mental or psychological problems. The breath, skin, or urine may also have a musty odor. If not treated, PKU can lead to permanent intellectual disability. All babies born in the United States and many other countries are screened for PKU using a simple blood test. There is no cure, but PKU can be managed with a diet low in phenylalanine. Also called phenylketonuria.