Friday, October 31, 2014

Unusually large dermal and subcutaneous rheumatoid nodules in a patient with severe rheumatoid arthritis.

Where do rheumatoid nodules typically occur?
These are typically present as asymptomatic, firm, fixed, or mobile subcutaneous nodules adjacent to bony structures. The most common site is the elbow . Other common locations include the extensor aspects of the fingers, flexor sheath tendons in the palms, Achilles tendons, ischial tuberosities, and sacrum. Rheumatoid nodules occur in approximately 25% of patients with rheumatoid arthritis.

What causes rheumatoid nodules?
The pathogenesis is not understood, but the evidence suggests that rheumatoid arthritis occurs in genetically susceptible patients after an arthritogenic microbial antigen exposure. The identity of the microbial trigger has not been established, although considerable attention has been placed on the Epstein-Barr virus. Once the process is initiated, a complex autoimmune disease develops characterized by increased numbers of CD41 T cells in the joint, which also
activate B cells that produce autoantibodies (primarily IgM) to the Fc portion of autologous IgG. The antigen that provokes the autoimmune response has not been fully established, but research is focusing on type 2 collagen, human cartilage glycoprotein-39, human stress protein BiP, and several different heat shock proteins. How this autoimmune response produces rheumatoid nodules is not clear.


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