Prevalence of rheumatoid arthritis in circumpolar native populations.

OBJECTIVE: To compare the prevalence of rheumatoid arthritis (RA) in related, but geographically separate, indigenous circumpolar populations. METHODS: Cases were identified by community survey in Russia and by examination of cases located through arthritis registries, a computerized patient information database, and query of local health care providers in Alaska. All possible cases were verified by examination and application of the American College of Rheumatology 1987 criteria. RESULTS: The prevalence rates of RA (age standardized to US population of 1980) varied from 0.62% in the Alaskan Yupik to 1.78% in the Alaskan Inupiat. The Russian Chukchi rate was 0.73% and that of the Siberian Eskimo was 1.42%. CONCLUSION: The Alaskan Yupik Eskimo and Chukchi natives had prevalence rates of RA within the usual range of North American Caucasian groups, in contrast to the Russian Siberian Eskimo and the Alaskan Inupiat Eskimo of the Barrow region, whose high rates approached those of unrelated North American native groups living in very different environments. The Alaskan Inupiat rate was significantly higher than that of the Alaskan Yupik (OR = 2.51, 95% CI 1.25-5.07; p = 0.013), but statistical inferences are limited in the Russian study populations by the small case numbers. The high prevalence rates probably have a genetic basis, although an environmental influence cannot be excluded.

Spondylarthropathic diseases in indigenous circumpolar populations of Russia and Alaska.

AIMS: To compare the nature and frequency of spondylarthropathy in geographically separated but genetically related populations with a high prevalence of HLA-B27. METHODS: Using a common questionnaire and disease criteria, cases were ascertained through cross-sectional community surveys in Russia and by examination and study of possible cases identified through rheumatic disease registries and the Native Health Service's computerized patient care data system in Alaska. RESULTS: Similar overall prevalences of spondyloarthropathy (2.0-3.4%) and a similar spectrum of disease were found, including reactive arthritis, ankylosing spondylitis and undifferentiated spondylarthropathy. Psoriatic arthritis was very rare. CONCLUSION: No predisposition to one particular form of spondyloarthropathy was observed; genetic and microbial settings for a spectrum of disease were present. Among adults positive for the presence of HLA-B27 the prevalence of all types of spondylarthropathies was estimated to be 4.5%, all populations combined, and the prevalence of AS was estimated to be 1.6%.

HLA-B27 subtypes among the Chukotka Native groups.

The purpose of this study was to assess the relative frequency of the known HLA-B27 subtypes in HLA-B27 positive Chukotka natives, which have higher frequencies of HLA-B27 (to 40%) and spondyloarthropathies (to 2%) than the Russian Caucasian population. Using oligotyping of the polymerase-chain reaction amplified second and third exons of the HLA-B27 gene in 86 DNA samples from HLA-B27 positive individuals were successfully typed. All had HLA-B*2705, including 4 patients with Reiter's syndrome and 5 with ankylosing spondyloarthritis, except one Eskimo who had HLA-B*2702. None had HLA-B*2704, a frequent subtype in Orientals. With respect to HLA-B27 subtypes the indigenous populations from the eastern part of the Chukotka Peninsula are genetically more closely related to Caucasians than to Orientalis.