PKU, an abbreviation for Phenylketonuria, is a genetic disorder that affects the way the body processes protein. People with PKU cannot properly metabolize an amino acid called phenylalanine, which can lead to severe health problems if left untreated. Synonyms for PKU include phenylalanine hydroxylase deficiency, phenylpyruvic oligophrenia, and Folling's disease. These terms all refer to the same condition and are used interchangeably in medical literature. While there is no cure for PKU, it can be managed with a carefully controlled diet low in phenylalanine. Early diagnosis and treatment are essential to prevent long-term complications.