Immunogenetic analysis of association between HLA antigens and psoriasis vulgaris: population and family studies.

A significant increase of some HLA antigens (B13, B17) was shown in 122 psoriasis patients, compared to 176 unrelated individuals of the control group. This finding is not completely secondary to an increase in Cw6, supporting the opinion that different loci within the HLA region are responsible for different forms of the disease. Some familial cases of psoriasis suggest a possible involvement of Bw35, despite the fact that the increase of this antigen in a random population was not significant for the corrected value. In this case it seems likely that a gene associated with Bw35 may be responsible for an infectious form of disease. The fact that 32% of our psoriatic patients did not show either B13, B17 or Cw6, indicated that the Is gene could also segregate with an other haplotype. The Is gene is also dominant, with an incomplete penetrance of B17 and Bw35 among relatives.