HLA-D related (DR) antigens in various kinds of myositis.

Forty-eight patients with various kinds of myositis were studied for HLA-A, B, C, and DR antigens and compared to both local and 7th International Workshop controls. No A, B, or C antigens were increased except for B8 in white patients (7/13 or 54%) (p = 0.005, pc = NS) and for B7 in black patients (6/9 or 67%) (p = 0.02, pc = NS). HLA-DR3 occurred in 8/12, or 67% of whites with polymyositis (PM) as compared to 23% of white controls (p = 0.003, pc = 0.02). HLA-DRw6 was found in 7/9, or 78%, of blacks with PM compared to 26% of black local controls (p = 0.005, pc = 0.04) and 38% of black Workshop controls (p-0.05, pc = NS). Dermatomyositis (DM) patients, however, showed no increased frequencies of any HLA antigens. HLA-DR4 was decreased overall (p = 0.005, pc = 0.04). These immunogenetic differences between PM and DM suggest that they are pathogenetically different disorders.