HLA-DRB1 and rheumatoid arthritis: The relation between the SEs and the severity of RA has not been clearly understood yet [32] in many studies that done in Northern Europe [33], Netherlands [34], Northern Italy [35], and Caucasians [35, 36]; showed that DRB1*0401 allele is indicated to increase the severity of RA whereas DRB1*0405 allele is mainly in Korea [37].