HLA-DRB1 and rheumatoid arthritis: The SE was first recognized due to an association between a five-amino-acid sequence motif in residues 70–74 of HLA-DRB1 alleles with severe rheumatoid arthritis (RA [MIM: 180300]),57,58 with the HLA-DRB1∗04 allelic group representing the most common SE-coding alleles.59