[The epidemiology of spondyloarthropathies among the native inhabitants of Chukotka. 2. The prevalence of HLA-B27 in the population and among spondyloarthropathy patients].

To establish the incidence of HLA-B27 among the indigenous population of Chukot Peninsula, a one-stage cross-sectional study was made of all the natives of the two settlements of eastern Chukot Peninsula (Sireniki and Novo-Chaplino). At the moment of examination altogether 640 natives lived in both settlements. Of these, 464 persons (72.5%) could be examined clinically; HLA typing could be performed in 439 persons (68.6%). Among the 439 natives examined, antigen B27 was identified in 141 cases (32.1%). Among Eskimos, the number of HLA-B27-positive individuals amounted to 39.7%, among Chukchi to 18.9% (p = 0.0005). Half-breeds occupied an intermediate position between the two groups. The frequency of NLA-B27-positive cases was 29.7% among them. 7 patients were diagnosed to have diseases belonging to the group of spondyloarthropathies. 2 persons presented with ankylosing spondyloarthritis, 2 with Reiter's syndrome, 2 with undifferentiated spondyloarthropathies and 1 with juvenile chronic arthritis. All the patients with ankylosing spondyloarthritis and Reiter's syndrome appeared HLA-B27-positive.