Phenylketonuria is an autosomal recessive genetic disorder, caused by a mutation in the phenylalanine hydroxylase gene leading to reduced enzyme activity. This results in the accumulation of phenylalanine and its metabolic products in the body, causing the disease. It is the most common congenital amino acid metabolism disorder and is clinically characterized by delayed intellectual development, changes in skin and hair pigmentation, and a mousy urine odor. The incidence of this disease in China is approximately 1 in 11,000, and it is inherited in an autosomal recessive manner.