Human leukocyte antigen alleles and susceptibility to psoriatic arthritis

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

Methods: 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.

Results: 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.

Conclusion: 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.