Histidinemia and infantile autism.

A 10-year-old boy first showed features of infantile autism at age 24 months. Histidinemia was also diagnosed, with histidine blood levels seven times higher than the upper normal values. If the coexistence of autism and histidinemia was not coincidental, histidinemia may have constituted a necessary but not sufficient factor leading to the clinical condition of autism. Other members of the patient's family had high blood levels of histidine, but did not show symptoms that have been related to histidinemia.