[Familial cases of multiple sclerosis when siblings reside in different climato-geographical zones].

A clinical study covered 11 patients with multiple sclerosis (MS) from 5 families (4 Russian and 1 Tatar family) born outside the Central Asia and then living for a long time in different climatogeographic regions of the USSR belonging to zones with varying risk of the disease: the probands have stayed in Uzbekistan while their ill siblings live in the Far East, Volga region, Urals, Tajikistan, and Kazakhstan. The ill siblings of each family irrespective of the place they live in have displayed the similarity of their age at the onset of MS, as well as the similarity of the clinical picture and the course of the process which suggests the involvement of genetic factors in the etiology of familial forms of the disease.