HLA-DRB1*04 alleles in psoriatic arthritis: Comparison with rheumatoid arthritis and healthy controls

Psoriatic arthritis (PsA) is an inflammatory arthritis associated with psor iasis usually seronegative for rheumatoid factor. An increased frequency of HLA-DR4 has been noted in PsA, particularly among patients with a rheumato id arthritis like (RA) arthritis. The aim of the current investigation was to compare HLA-DRB1*04 alleles in patients with PsA, patients with RA, and healthy controls. Sample size calculations based on the frequency of HLA-DR 4 suggested that 90 individuals in each patient group would be sufficient t o address our question. Therefore, 90 HLA-DRB1*04 positive patients from ea ch patient group underwent high resolution molecular typing and were includ ed in this study. Although HLA-DRB1-*0401 was the most frequent allele in a ll groups, its frequency among the PsA patients was lower than that of RA p atients and controls. HLA-DRB1*0402 was higher among patients with PsA. Pat ients with RA were more likely to have more than one shared epitope allele than either PsA or the healthy control group. HLA-DQB1 alleles did not cont ribute further information, We suggest that the differences in the class II HLA epitope(s) may also be related to interaction specificity with another molecule functioning in the immune response to a putative arthritogenic an tigen and result in differences in disease expression. (C) American Society for Histocompatibility and Immunogenetics, 2001. Published by Elsevier Sci ence Inc.