Immunogenetic profile of psoriasis vulgaris: Association with haplotypes A2, B13,Cw6,DR7,DQA1*0201 and A1,B17,Cw6,DR7,DQA1*0201

Abstract: Psoriasis vulgaris is a skin disease with an immunological and genetic background present in 1–3% of the population. We studied the genetic susceptibility to psoriasis vulgaris in Finns with serological HLA typing and genomic HLA class II typing of the DQ and DP loci to evaluate the risk of developing psoriasis. The haplotypes most frequently distinguishing between psoriatics and controls were those that carried Cw6 (P<10⁻⁸), DQA1^*0201 (P=9.3×10⁻⁶) and DR7 (P=3.9×10⁻⁵). The two most frequent marker haplotypes were A2,B13,Cw6,DR7,DQA1^*0201 and A1,B17,Cw6,DR7,DQA1^*0201, which were not found among the control subjects. A deficit of haplotype B8,DR3,DQ2 (2 out of 124 in the patients versus 15 out of 106 in the controls,P=1.5×10⁻⁴) was found, and this was in accordance with a slightly decreased frequency of DQA1^*0501 (P=3.1×10⁻²), which was usually linked with this haplotype. These results stimulate the search for a genetic resistance factor in psoriasis. Thus, this report sheds further light on the immunogenetic background of psoriasis in Finland. We conclude that the inheritance of psoriasis has a polygenic mode, in which the Cw6,DR7,DQA1^*0201 combination seems to be important (P=7.5×10⁻⁷, relative risk 24.4, aetiological factor 0.29).