Human leukocyte antigen alleles and susceptibility to psoriatic arthritis

Our purpose was to determine associations between HLA alleles and psoriatic arthritis (PsA).

678 PsA cases and 688 healthy controls were analyzed in a case-control design. The difference in the proportion of cases and controls with at least 1 copy of HLA alleles were tested for significance using χ(2) test and Fisher's exact test. Association analyses of haplotypes inferred by the Expectation-Maximization algorithm were performed. In the family-based association study, data from 283 families were analyzed.

Univariate analysis revealed that cases were more likely to be carriers of HLA-C*01, -C*02, -C*06, -C*12, -B*27, -B*38 and -B*57, whereas controls were more likely to be carriers of HLA-C*03, -C*07, -B*07, -B*51, -DRB1*15 and -DQB1*0602. In haplotype analyses, PsA cases were more likely to be carriers of the HLA haplotypes -C*01/-B*27, -C*02/-B*27, -C*12/-B*38, and -C*06/-B*57, while controls were more likely to be carriers of the haplotypes -C*07/-B*07 and -C*15/-B*51. In the family-based association analysis, the HLA alleles -A*02, -B*27 and -DRB1*07 were preferentially transmitted to cases, whereas the alleles -A*03, -A*28, -B*51, -DRB1*11 and -DQB1*0301 were under transmitted.

This large case-control and family based association study shows that HLA-C*12/B*38, HLA-B*27 and HLA-C*06/B*57 are haplotypes (alleles) robustly associated with PsA. However, since patients with PsA also have psoriasis it is difficult to determine whether the primary association is with arthritis or psoriasis.