[Clinico-genetic diagnosis of severe mental retardation].

Among 330 patients with severe mental retardation who were consulted at random for medico-genetic purposes (excluding phenylketonuria and Down's disease), 27,3% constituted retarded patients due to genetic diseases, 10%--to exogenous factors. Families with a high genetical risk (25%-50% for sibs) constituted 20%. In the group of patients with severe mental retardation, but without signs of organic lesion in the neurological state or multiple congenital anomalies, there was a higher percentage of consanguineous parents and affected sibs, than in the group of patients with residual-organic neurological changes and in the group of patients with the so-called malformation retardation syndromes.