A previous report suggested that plasma dopamine-beta-hydroxylase (DBH) is elevated in childhood autism. We measured plasma DBH in 15 Children with functional psychosis and in 10 psychotic children with known organic etiology. DBH activity was significantly elevated in the children with functional psychoses and showed a significant correlation with age that is not reported for this age range in normals. It is possible that children with functional psychoses show an abnormal continuation of the rise in plasma DBH activity characteristic of infancy. No differences between children with functional psychoses and children with organic psychoses were found for red blood cell catechol-O-methyl-transferase, plasma monoamine oxidase, or plasma cyclic AMP.

Plasma cyclic AMP is a "second messenger" that may reflect levels of activity of important neurotransmitter receptors. Plasma cyclic AMP was measured in 18 patients with childhood autism, 7 patients with pervasive developmental disorder, and 12 age- and sex-matched healthy controls. Plasma cyclic AMP was significantly elevated by over 100% in both groups of patients with childhood-onset psychoses compared with controls. Plasma cyclic GMP, a nucleotide linked to different receptors, was not elevated, suggesting that the finding may be specific.