A family study of 274 index patients with limb reduction malformations born in Hungary from 1975 to 1977 is reported. The majority of 789 first-degree relatives were personally examined. Information was collected on 1094 uncles and aunts and on 1095 cousins, and those affected by limb malformations were examined. Among 789 first-degree relatives six were affected by a similar malformation (radial, ulnar and central ray defects) and 1 by a malformation of a different type; no secondary cases of the same type were found among the relatives of patients with terminal transverse and amniogenic malformations, and with limb malformations which were part of syndromes or unclassifiable associations with other malformations. While a few rare types of limb defects are due to dominant genes, the aetiology of most cases is obscure. There is no evidence of sex-linked inheritance, of multifactorial causation or of environmental factors shared by relatives. These results are similar to those of an earlier study by Birch-Jensen.
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