In a recent genome-wide study of RA with a relatively large sample size, Plenge et al. [3] identified a genome-wide significant association signal on chromosome 9 close to TRAF1 and C5 in addition to confirming known genes related to RA (e.g., HLA-DRB1 in major histocompatibility complex (MHC) region and PTPN22) [3]. Here, HLA-DRB1 is linked to rheumatoid arthritis.