HLA and complement C4 studies in psoriasis vulgaris.

BACKGROUND

Psoriasis vulgaris is known to be associated with the presence of certain HLA antigens and complement factors but only studies of Western populations have been reported. We investigated the HLA and complement profile in Indian patients with psoriasis vulgaris.

METHODS

Sixty-seven patients and 132 normal subjects were typed for class I antigens using 262 sera, and 55 patients and 104 normal subjects were typed for class II antigens using 174 sera. The sera from patients and normals were sent to Japanese laboratories for the study of class III antigens.

RESULTS

The study revealed that patients had an increased frequency of A1 (p < 0.0025), B17 (p < 0.0025), Cw6 (p < 0.001) DR7 (p < 0.05) and DQw3 (p < 0.005) when compared to normal controls. Analysis of two and three antigen haplotypes revealed a significant increase in the incidence of all haplotypes involving those antigens which showed a high frequency among patients. A significant association was also found with complement factors C4A6.3 and C4A6,X. However, the relative risk was high for C4BQO (10.73).

CONCLUSIONS

Psoriasis in Indians is associated with the A1, B17 and Cw6 but not with B13 antigens and the complement allotypes mentioned above. The strong association with C4 factors may be as a result of a close linkage between the class III region and Ir genes.