Class I HLA antigens in spondyloarthropathy: observations in Alaskan Eskimo patients and controls.

Objective. To assess the role of HLA-B27 and other class I histocompatibility antigens in overall risk and clinical manifestations of spondyloarthropathy (SpA) in Alaskan Eskimos. Methods. Class I antigens were studied in 104 patients with SpA and in 111 controls. The frequencies of HLA-A, B, and Cw antigens were determined in patients with SpA with various clinical manifestations and compared to frequencies observed in controls. Results. Only HLA-B27 differed significantly in cases and controls. Except for B27, no association of particular antigens with specific syndromes or disease features was found. Patients with B27 had more extraarticular manifestations than patients who lacked B27 antigen. Patients putatively homozygous for B27 did not appear to have more severe disease than those who were heterozygotic. B27 was most closely associated with ankylosing spondylitis [odds ratio (OR) = 210], less so with reactive arthritis (OR = 12.9) and undifferentiated SpA (OR = 4.6). Conclusion. Observations in other population groups that implicated B27 cross reactive group (CREG) and other A, B, and Cw antigens as risk factors for developing SpA were not confirmed in Alaskan Eskimos. Nor were CREG or other B antigens either alone or in combination with B27 associated with specific clinical syndromes. Only HLA-B27 was strongly associated with disease and with extraarticular manifestations.