HLA antigens in polymyalgia rheumatica in northern Sweden.

The HLA-A, B and DR antigens were analyzed with serological methods in 75 patients with polymyalgia rheumatica (PMR). In PMR patients the frequency of the HLA-DR4 antigen was significantly higher (62.1%) compared to blood donors (40%), p < 0.05, but did not differ from patients with seropositive rheumatoid arthritis (RA) from the same area (63.1%). In contrast, the frequency of HLA-B27 in the PMR patients (9.3%) was significantly lower compared to RA (27.2%), p < 0.01, but did not differ from blood donors (16.9%). There was no association between DR4 and disease affliction or severity in PMR. The increased frequency of HLA-B27 in RA but not in PMR in the population of northern Sweden suggests an immunogenetic difference between these two HLA-DR4 associated diseases.