Phenylketonuria (PKU) is a genetic disorder caused by reduced or absent PAH activity, which can also lead to decreased melanogenesis due to tyrosine inhibition and accumulation of hydroxyphenylpyruvate in the body due to hydroxyphenylpyruvate inhibition. The disease is autosomal recessive, with the mutated gene located on the long arm of chromosome 12 (12q24.1), and a small variation in this gene can cause the disease, not due to a gene deletion. It is an inherited disease caused by the marriage of two heterozygotes and is most common in the offspring of consanguineous marriages, with approximately 40% of the affected siblings affected. The basic biochemical abnormality of the disease is a deficiency of phenylalanine hydroxylase in the liver due to a mutation in the phenylalanine hydroxylase gene. The severity of the clinical manifestations varies greatly if the base pairs in which the mutations occur are different, and can present as typical PKU or mild hyperphenylalaninemia. Genetic diseases are difficult to treat and have unsatisfactory outcomes, making prevention even more important. Preventive measures include avoiding consanguineous marriage, promoting genetic counseling, carrier genetic testing and prenatal diagnosis and selective abortion to prevent the birth of affected children. Promote breastfeeding. Early detection of carriers of phenylketonuria and popularization of iron trichloride diapers to enable early detection and early treatment of infants who have caused the disease are important ways to prevent low intelligence. It is also important to develop good habits and not to smoke. You need to keep a good mind, stable emotions, have a healthy diet, and eat more fruits and vegetables in general to improve your self-immunity. People who must work at heavy fumes, try to protect themselves, such as wearing a mask, going out regularly to get some fresh air, having a check-up at least once a year, etc. Stay away from smoke, alcohol, drugs, radiation, pesticides, noise, volatile harmful gases, toxic and harmful heavy metals, etc.