Phenylketonuria is an autosomal recessive genetic disorder primarily caused by mutations in the phenylalanine hydroxylase gene. This leads to reduced activity of phenylalanine hydroxylase, accumulation of phenylalanine and its metabolites in the body, and the onset of the disease. Phenylketonuria is the most common congenital amino acid metabolism disorder. Clinically, it is mainly characterized by intellectual developmental delays, light skin and hair pigmentation, and a mousey urine odor. The incidence of this disease varies by ethnicity and region. In China, the incidence is approximately 1 in 11,000.