Phenylketonuria is a relatively common autosomal recessive disorder caused by an enzyme defect in the phenylalanine metabolic pathway. It is common in the offspring of consanguineous marriages, and 40% of the affected siblings may have the disease. However, the lack of phenylalanine hydroxylase in the liver due to mutations in the phenylalanine hydroxylase gene is the most basic biochemical abnormality of the disease, but the severity of the clinical manifestations may vary greatly if the base pairs of the mutations are found to be different, so that typical phenylketonuria may include some mild manifestations of hyperphenylalaninemia. Phenylketonuria is an autosomal recessive genetic disorder, and after this disease is diagnosed, we may need further typing, whether it is classic or atypical, and the medication treatment and diagnosis are not quite the same, so we need further genetic testing or related tests to further enable these children to be further diagnosed and treated, and to reduce the occurrence of some of his sequelae.