HLA-DRB1 and rheumatoid arthritis: In our study population, we found the HLA class II alleles, DRB1*04:04 and DRB1*04:05, which have been described as associated with susceptibility to rheumatoid arthritis [38,39,40], while the DRB1*03:01 allele with Systemic Lupus Erythematosus [41,42].