[Families with 2 oligophrenic siblings].

Under observation there were 27 families with two mentally deranged sibs in each born by intellectually normal parents. In 2 of 24 families, the clinical picture of the derangement in the sibs was different, and in the rest of 22 identical. In 3 families, a sex-linked recessive oligophrenia with a nonspecific clinical picture was diagnosed. Prevalent were clinically non-differentiated forms of the oligophrenia. In 2 families, the oligophrenia was combined with clinical signs of hereditary defects of metabolism. Parents' consanguinity was registered in 4 families.