Platelet monoamine oxidase in children with infantile autism.

Platelet monoamine oxidase activity was measured in 9 autistic subjects and 9 controls. There were no significant differences in the rates of metabolism of 5-hydroxytryptamine, dopamine or tyramine between the two groups, although the rate of metabolism of tyramine was more rapid than 5-hydroxytryptamine or dopamine within each group. It is concluded that the data presented do not support the view that measurement of platelet monoamine oxidase can be used as a biochemical index to aid in the clinical diagnosis of infantile autism.