In which condition does the accumulation of phenylalanine occur due to enzyme deficiency?

Phenylketonuria (PKU) is a metabolic disorder that arises from a deficiency in the enzyme phenylalanine hydroxylase. This enzyme is responsible for converting phenylalanine, an amino acid obtained from dietary protein, into tyrosine. When this enzyme is deficient or inactive, phenylalanine accumulates in the body, leading to toxicity and potential neurological damage if not managed.

The accumulation of phenylalanine is particularly concerning because it can affect cognitive development, and individuals with untreated PKU can experience intellectual disabilities, seizures, and other serious health issues. Early detection through newborn screening and a strict low-phenylalanine diet can effectively prevent the adverse effects of this condition, highlighting the importance of recognizing this enzyme deficiency.

The other conditions listed—maple syrup urine disease, homocystinuria, and alkaptonuria—are associated with different metabolic pathways and enzyme deficiencies, which do not involve the accumulation of phenylalanine.