phenylketonuria

Inherited metabolic condition in which the liver cannot control the level of phenylalanine (an amino acid derived from protein food) in the bloodstream. The condition must be detected promptly and a special diet started in the first few weeks of life if brain damage is to be avoided. Untreated, it causes stunted growth, epilepsy, and severe mental disability.

The ‘heel prick’ test has been used routinely since the 1970s to detect the disorder in newborn children. It was the first screening for a genetic disease to be introduced.