X-linked agammaglobulinemia and rheumatoid arthritis

The pathogenic role of B cells in rheumatoid arthritis (RA) has recently gained much interest by the marked clinical responses of anti-CD20 therapy in RA. We describe a patient with X-linked agammaglobulinemia (XLA) who presented with an erosive symmetrical polyarthritis with histological features of RA including formation of a destructive pannus. Furthermore, the patient also developed subcutaneous nodules that were histologically undistinguishable from rheumatoid nodules. Surprisingly, lymphocytic infiltrates in both synovium and nodule consisted almost exclusively of CD8 T cells. Although some peculiar B cell subsets have been described in XLA patients, no B cell subsets could be demonstrated in synovial tissue or the subcutaneous nodule. This case illustrates that classical RA can develop in the absence of mature B cells.