Pannus

Last revised by Hoe Han Guan on 30 Dec 2022

Pannus describes an abnormal layer of granulation tissue. It is usually seen overlying joint surfaces (usually in the setting of rheumatoid arthritis, though pannus can be a feature of other inflammatory arthropathies), prosthetic heart valves, or overlying the cornea 1

A key step in the pathogenesis of rheumatoid arthritis is pannus formation. Within the joint space, pannus refers to hyperplastic, thickened synovium, which forms as a consequence of persistent synovial inflammation. It is a highly cellular tissue, containing macrophages and synoviocytes, among other components. The pannus adheres to the adjacent articular cartilage, and enzymes within the pannus cause cartilaginous destruction. The pannus subsequently invades the subchondral bone, resulting in the characteristic radiographic findings of erosions 2. Osteoclasts further contribute to bone destruction 3. Common sites of pannus formation in rheumatoid arthritis include the metacarpophalangeal and metatarsophalangeal joints, and around the odontoid peg.

History and etymology

Pannus is Latin for “cloth”.

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