Phenylketonuria is an autosomal recessive genetic disorder resulting from mutations in the phenylalanine hydroxylase gene, leading to reduced enzyme activity and the accumulation of phenylalanine and its metabolic products in the body, thereby causing this disease. Phenylketonuria is the most common congenital amino acid metabolic disorder, clinically characterized by intellectual developmental delays, light skin and hair pigmentation, and a mouse-like urine odor. The incidence of the disease varies by race and region, with an incidence rate in China of about 1 in 11,000. Phenylalanine is an essential amino acid for the human body, but due to reduced activity of phenylalanine hydroxylase, phenylalanine cannot be converted into tyrosine, leading to extremely high concentrations of phenylalanine in the blood, cerebrospinal fluid, and tissues. Abnormal metabolism produces a large amount of phenylpyruvic acid, phenylacetic acid, phenyllactic acid, and p-hydroxyphenylacetic acid, along with high concentrations of phenylalanine and its metabolic products, causing brain damage and corresponding symptoms.