HLA-CW*0602 is a susceptibility factor in type I psoriasis, and evidence Ala-73 is increased in male type I psoriatics.

We investigated the HLA-C locus of 87 unrelated patients with chronic plaque psoriasis by genotyping with sequence-specific amplification primers. The HLA-Cw*0602 allele was significantly increased in male and female type I psoriatics but not significantly increased in either male or female type II psoriatics. The overall frequency of Ala-73 (present in Cw*04, Cw*0602, Cw*07, Cw*12, Cw*1503, and Cw*17) in psoriatics was 88.5% but the incidence of Ala-73 in our Caucasian controls was also high at 84.3%. Ala-73 was present in 97.2% of type I and 85.7% of type II male psoriatics (chi2 = 8.43, p = 0.001; chi2 = 0.01, p = nonsignificant, respectively), in contrast to 81.5% of type I and 80% of type II female psoriatics (nonsignificant). HLA-Cw*0602 appeared more discriminating in determining disease susceptibility in our population than Ala-73, in line with earlier serologic studies implicating HLA-Cw6. Thus, although the frequency of HLA-Cw*0602 decreased from 54.0% in type I to 29.2% in type II psoriatics, the overall frequency of Ala-73, present in 90.4% of type I and 83.3% of type II psoriatics, did not. (i) Thus this study confirms the strong association between psoriasis and HLA-Cw*0602 by using sequence-specific amplification primers. (ii) Results show that Ala-73 on HLA-C molecules is increased in frequency in psoriasis, but results observed show an association more subtle than previously thought, with HLA-Cw*0602 playing the major role. (iii) This report documents the differential association of HLA genes in male and female psoriatic patients. An interaction between gender and immunogenetics may influence susceptibility to psoriasis.