Several papers have shown evidence of B‐cell clonal expansions in the synovial tissue of patients with RA.92, 94, 99, 105, 108 Indeed, in a prospective study of 21 individuals at risk of RA, the risk of developing RA during follow‐up was significantly associated with the presence of ≥ 5 dominant BCR clones, defined as clonally related BCRs representing > 0·5% of the total repertoire.108 This was validated in an independent prospective cohort of 50 at‐risk individuals. This evidence concerns the gene BCR and rheumatoid arthritis.