HLA-DRB1 and rheumatoid arthritis: Among the genetic components, expression of specific polymorphisms of human leukocyte antigen (HLA)-DRβ1 (the so-called “shared epitope” (SE)) is most frequently cited as enhancing the risk of RA and predicting a worse outcome in individuals expressing one or more susceptibility alleles that encode a linear sequence of amino acids in the DRβ1 chain of the HLA‐DRα/β heterodimer between amino acids 67 and 74 (QKRAA in *0401, QRRAA in *0404, *0405, and *0101, and RRRAA in *1001) [1].