HLA-DRB1 and rheumatoid arthritis: In this study, HLA-DRB1*03/DRB1*03, HLA-DRB1*04/DRB1*03, HLA-DRB1*08/DRB1*3, HLA-DRB1*13/DRB1*02, and HLA-DRB1*13/DRB1*03 haplotypes, were associated with RA risk.