Examination of urine samples from patients exhibiting various incompletely described diseases recently revealed an abnormality in amino acid excretion in a child affected by a severe mental condition suggesting autism. This abnormality in amino acid excretion was also detected in the younger sibling of the patient, although the sibling has not displayed any abnormal mental effects to the present time. Further investigations of the patient demonstrated a deviation in the decarboxylation pathways of tryptophan metabolism, probably secondary to some other metabolic alteration.
A number of studies in recent years have clearly demonstrated the relationship between body chemistry and mental function. In the case of phenylketonuria there is no longer any doubt that specific inherited alterations in the metabolism of phenylalanine are responsible for the oligophrenia found in affected persons, as demonstrated by regression or prevention of the mental abnormalities when susceptible persons are placed on a phenylalaninefree diet.1-3 There