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Question: How does pannus lead to articular destruction in RA?


Although the source of stimulation for the synovial swelling and development of pannus that occurs in RA has not been entirely elucidated, concepts are emerging. The presence of specific adhesion molecules may support the attachment of pannus to articular cartilage since normal cartilage does not support the adhesion of pannus. There is also a preponderance of proinflammatory cytokines within the synovium and synovial fluid-mainly TNF-alpha, IFN-alpha, and IL-15. These in turn lead to cellular activation and production of metalloproteinases, cathepsins, and other destructive enzymes. RANK-L production leads to osteoclast activation, almost certainly the principle source of bone loss in RA. Although the exact mechanism remains a mystery, it appears that articular damage in RA results from cartilage destruction that is a direct consequence of a relentless inflammatory attack that includes both pannus formation and soluble inflammatory mediators.

Reference: Hochberg MC (ed). Rheumatology, 3rd ed. St. Louis, Mosby, 2003

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