Psoriasis arthropathy and HLA-B51: report of 5 cases.

Psoriasis arthropathy (PsA) is a chronic inflammatory arthropathy characterized by the association of arthritis with psoriasis. Although the precise mechanisms of PsA still remain obscure, several genetic and environmental factors have been suggested to play important roles. HLA-B51 has been strongly associated with Behçet's disease; however, its association with PsA has not been documented. We describe herein five Japanese patients (4 males and 1 female) with PsA and positive for HLA-B51. The clinical forms defined by Moll and Wright revealed that the polyarticular pattern was noted in two cases, and oligoarticular, distal, and spondyloarthropathy patterns were noted in one case each. Positive rheumatoid factor was detected in one patient, and antinuclear antibody in two patients. The other HLA subclasses were A2 and A31 in 3 cases, respectively. HLA-B51 was detected in 5 out of 17 patients with PsA examined in our department; in contrast, HLA-B51 was not detected in 17 patients with psoriasis vulgaris. Our observations suggest that HLA-B51 may play a role in the pathogenesis of PsA in the Japanese population.