[Genetic factors in the etiology of undifferentiated oligophrenia].

A clinico-genetical study of 262 families of patients with clinically nondifferentiated oligophrenia established that genetical factors play an important role in its etiology. According to the mechanism of inheritance these families were divided into 2 groups: a group of families with a monomeric inherited oligophrenia (58) and a group of families (204) where oligophrenia is inherited as a simple mendelian sign, and in relation to this group polymeric mechanisms of inheritance are more acceptable. Both groups differ by the frequency of secondary cases, the degree of defect in the patients, coefficient of inbreeding. The second group of nondifferentiated olgophrenia is especially difficult for an etiological differentiation, because it is quite possible that they include cases with exogenously determined oligophrenia.