Biology of gouty tophus

especially articular cartilage, ligaments, tendons and bursae. Tophi are composed of multiple lobules separated by fibrous septa. Urate crystal deposition which occurs at the center of each lobule is surrounded by a cellular zone, called corona zone, and a fibrovascular zone. The corona zone is enriched in macrophages and multinucleated giant cells. These multinucleated giant cells express osteoclast markers, inflammatory cytokines and proteolytic enzymes and may be involved in bone destruction. The exact mechanisms of urate crystal formation and growth are still unknown. Increased serum urate level is necessary but not sufficient for crystal formation which depends on local and systemic factors including temperature, pH, ionic strength and extracellular matrix macromolecules. Tophi management relies on urate-lowering therapy with a low target of serum urate level that permits their fast dissolution. (c) 2022 l'Academie nationale de medecine. Published by Elsevier Masson SAS. All rights reserved.