Phenylketonuria is a common amino acid metabolic disease. Most infants appear normal at birth and do not show any specific clinical symptoms during the neonatal period, although some newborns may experience symptoms such as feeding difficulties, vomiting, or irritability. Symptoms of phenylketonuria gradually appear in the first three months after birth, including changes such as hair turning from black to yellow, skin whitening, delayed growth and intellectual development, seizures, hyperactive reflexes, eczema, etc. The sweat and urine of affected children will have a mouse-like odor.