What is amyloid arthropathy?

Updated: May 09, 2019
  • Author: Robert O Holmes, Jr, DO; Chief Editor: Herbert S Diamond, MD  more...
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Articular and periarticular consequences of amyloidosis often mimic rheumatoid arthritis (RA), polymyalgia rheumatica, autoinflammatory syndromes, seronegative spondyloarthritis, and plasma cell dyscrasias. [86] Whether causal or just associated, various autoimmune diseases can also predispose to the deposition of amyloid fibrils. Amyloid deposition in inflammatory syndromes is amplified by the underlying inflammatory state, significantly increasing morbidity and mortality, especially in the case of renal amyloidosis. [87] However, autopsy study shows that amyloid arthropathy in RA is often undiagnosed in patients with long-standing severe RA. [88]

Amyloid arthropathy is classically seen in the shoulders, knees, wrists, and elbows, and this may be explained by that fact that these are sites that are commonly aspirated. Amyloid arthropathy can mimic classic RA but usually lacks the intense distal synovitis and can affect the hips, knees, and shoulders more than peripheral joints. [89]

Synovial fluid may contain amyloid fibrils, although it is not particularly inflammatory, with white blood cell counts on average less than 2000 cells/µL. Synovial biopsies reveal marked synovial villi hypertrophy. The classic “shoulder-pad” sign denotes end-stage amyloid deposits in the shoulder synovium and periarticular structures, but is rarely seen.

Another articular structure commonly affected by amyloid deposition is the carpal tunnel. Carpal tunnel syndrome can be the presenting sign of primary or secondary forms of amyloid, as only minimal deposits are required to impair nerve conduction. The diagnosis can be made with biopsy at the time of carpal tunnel release surgery or other joint procedures. It can be helpful to obtain pathology even on routine carpal tunnel release surgeries, as this is a great opportunity for a tissue diagnosis. In a pathology review of 124 patients undergoing carpal tunnel release without a previous diagnosis or clinical signs of amyloidosis, 82% had amyloid deposition. At 10-year follow-up, only 2 patients had systemic amyloidosis diagnosed after amyloid was discovered in their tenosynovium. [90]

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