Localized amyloid deposition in cartilage is glycosaminoglycans‐associated

Localized amyloid deposition is known to occur commonly in the articular cartilage of elderly patients. Its pathogenesis is uncertain and it is not known if other cartilage‐containing tissues also contain amyloid deposits. Systemic amyloid deposits are known to contain highly sulphated glycosaminoglycans, a major constituent of cartilage. As the composition of articular cartilage glycosaminoglycans is known to change with age, we sought to identify whether localized amyloid deposition in cartilage was glycosaminoglycan‐related. We examined specimens of articular cartilage over a wide age range and also examined a variety of cartilaginous tumours and tumour‐like lesions for the presence or absence of amyloid deposits. Using mucin histochemistry (alcian blue: MgCl2 critical electrolyte concentration) and immunohistochemistry, we found that highly sulphated glycosaminoglycans (0.9 M and 1 M MgCl2), in particular keratan sulphate, localized to amyloid deposits in both articular cartilage and loose bodies derived from the articular surface. Other cartilaginous lesions (including loose bodies of primary synovial chondromatosis) were negative for amyloid and did not contain highly sulphated glycosaminoglycans. These findings suggest that changes in specific highly sulphated glycosaminoglycans may play a role in localized amyloid deposition in articular cartilage.