HLA-DRB1 and rheumatoid arthritis: HLA-DRB1*04:05:01, DRB1*10:01:01, DQB1*04:01:01, and DPB1*02:01:02 alleles have been identified as RA risk alleles in Chinese Han patients, with specific haplotypes like HLA-DRB1*04:05:01 ~ DQB1*04:01:01 also present.[8] Additionally, the HLA-DRB1*04 allele is associated with anti-citrullinated protein antibody (ACPA)-positive RA in Malaysian Chinese individuals.[9] These findings suggest that relying solely on data from one Han subgroup can significantly underestimate the genetic heterogeneity of RA risk factors.