Images in clinical medicine: Tophi.

Tophi (plural of tophus, Latin for "stone") are stone-like deposits of monosodium urate in the soft tissues, synovial tissues, or in bones near the joints. They are pathognomonic for gout, the most common inflammatory arthritis in the United States, with an estimated lifetime prevalence of 4%. It is usually the end result of loss of the balance between uric acid production and excretion. It can be found anywhere in the body especially in areas of friction or trauma. It is usually painless and rarely to present as the initial manifestation of gout. It is diagnosed mainly clinically. Imaging is mainly used to assess the complication like bony erosions. The American College of Rheumatology (ACR) guidelines currently indicate that urate-lowering therapy should be initiated in patients with the presence of tophi visible on examination or imaging (ACR Evidence A). First-line therapy for urate lowering remains the xanthine oxidase inhibitor allopurinol. The ACR currently recommends colchicine, 0.6 mg (or 0.5 mg) once or twice daily, or low dose NSAIDs should be continued to reduce gout flare incidence for six months after resolution of the tophus. Daily prednisone ≤10 mg has been endorsed as an acceptable second-line prophylactic agent.