HLA-DRB1 and rheumatoid arthritis: It is possible, that the +49A/G polymorphism does not increase disease susceptibility alone, but together with other predisposing factors, it increases the risk for developing RA, as some studies [17, 30, 31] demonstrated an association in HLA-DRB1*04 patients, while others [16, 22] found no association irrespective of the HLA-shared epitope status.