High prevalence of HLA-Cw1 and Cw2 antigens in spondylarthritis.

HLA-B27 is frequently, but not invariably, found in patients with spondylarthritic diseases. Recently it has been shown that HLA-C-locus antigens w1 and w2 (w1/2) are in linkage disequilibrium with B27. A group of 139 patients with seronegative arthritis or spondylitis has been studied to determine the clinical and radiographic features associated with these antigens. An increased frequency of spondylarthritis was present in HLA-B27-negative, Cw1/2-positive patients when compared with B27- and Cw1/2-negative patients (P less than 0.01). In addition, a large group of patients who did not fulfill accepted criteria for a specific spondylarthritic syndrome were identified; the frequency of both HLA-B27 and Cw1/2 was greater in these individuals than in healthy blood donors. Thus HLA-Cw1/2 are spondylitis-associated antigens. These findings suggest that the critical genetic locus is neither B27 nor Cw1/2 but is a closely linked gene.