Frequency of HLA antigens in patients with psoriasis or psoriatic arthritis

A study of 138 patients with psoriasis--74 with psoriasis alone and 64 with psoriatic arthritis--revealed a significantly increased frequency of the HLA antigens A1, A28, B13, DR7 and MT3 in those with psoriasis alone and of Bw39 in those with psoriatic arthritis. The frequency of B17 was higher in both patient groups than in a control group of healthy individuals. The frequency of DRw6 was slightly higher in the patients with psoriasis alone (17.8%) than in the controls (4.7%), and that of DR7 was higher in the patients with psoriatic arthritis (52.9%) than in the controls (32.6%). Elevated levels of serum IgG and IgA along with positive results of tests for antinuclear antibody or rheumatoid factor or both were present in less than a tenth of the patients with psoriatic rash alone and in up to a third of those with psoriatic arthritis. Psoriatic arthritis was found to be less likely to develop in patients with purely guttate psoriasis than in those with other types of psoriasis. Clinical subtypes of psoriatic rash or psoriatic arthritis were not associated with the presence of particular HLA antigens.