Inherited metabolic diseases and pathogenesis of mental retardation.

Continuing progress has been made in the exploration of the biochemical causes of mental illness. Recent research has indicated that selected abnormalities of specific isoenzymes play an important role in the pathogenesis of heritable metabolic disorders such as phenylketonuria and Niemann-Pick disease. The roles of "animal lectins" and glycosidic enzymes in brain development and synaptogenesis appear to have received important substantiation within the past year. In additions, it has been shown that the blood-brain barrier can be temporarily altered so that exogenous enzymes can enter the central nervous system, and imperative consideration for enzyme replacement therapy in mental disorders. Less satisfactory progress has been made concerining potential anabolic disorders of lipids affecting the nervous system. Finally, novel experimental directions concerning energy metabolism by the brain offer considerable hope for the elucidation of some of the causes of mental retardation.