PKU, or phenylketonuria, is a genetic disorder that affects how the body processes an amino acid called phenylalanine. People with PKU cannot break down phenylalanine properly, leading to its accumulation in the body, which can cause serious health issues, including intellectual disabilities and neurological problems if not managed. PKU is typically diagnosed through newborn screening tests. Treatment involves a strict diet low in phenylalanine, which is found in high-protein foods like meat, dairy, and certain grains. Individuals with PKU may also need special medical foods and supplements to ensure they receive adequate nutrition while avoiding harmful levels of phenylalanine.