Phenylketonuria is a common autosomal recessive genetic disorder due to a deficiency in the enzymes involved in the metabolic pathway of phenylalanine. It is a genetic metabolic disease. After the birth of a child, newborn screening is conducted for this disease. If a child is diagnosed with phenylketonuria or suspected of having the condition, it is common to visit a pediatric neurology department at a children's hospital. Phenylketonuria mainly causes varying degrees of intellectual disability, and some children may even experience epileptic seizures. Additionally, about 90% of affected children gradually develop lighter skin and hair, reduced iris pigmentation, dry skin, eczema, and a distinctive mouse-like urine odor, which is due to the excretion of phenylacetic acid in urine and sweat. It is a challenging genetic metabolic disorder to treat, requiring special dietary management. It is advisable to bring the child to the pediatric neurology department. Some hospitals may have a specialized department for genetic metabolic diseases. If such a department is available, it is recommended to consult there; otherwise, pediatric neurology is the appropriate alternative.