Phenylketonuria is a common amino acid metabolic disease, primarily caused by a deficiency of phenylalanine hydroxylase in the metabolic pathway of phenylalanine, preventing phenylalanine from converting into tyrosine. This leads to the accumulation of phenylalanine and its ketones in the body, which are then excreted in large amounts through urine. Its clinical manifestations are not uniform. The main clinical characteristic is intellectual disability, thus it does affect intelligence. Additionally, it can present various neuropsychiatric symptoms such as increased muscle tone, hyperreflexia, agitation, hyperactivity, convulsions, etc. It can also lead to reduced skin pigmentation and yellowing of hair among other symptoms. This disease can impact intelligence.