Gouty Tophi in Sinus Tarsi of Bilateral Feet Mimicking Synovial Sarcoma:A Case Report.

Chronic gout is defined as accumulation of monosodium urate crystals in joints, cartilage, tendons, bursae, bone, and soft tissue. The foot is the most common location for acute gout flares, with the first metatarsophalangeal joint being the most frequent site of tophus formation. However, few studies have reported gouty tophus formation in the subtalar joint. Gout has been termed the "great mimicker" because of its tendency to mimic other pathologic conditions, such as pigmented villonodular synovitis and synovial sarcoma. Herein, we present a rare case of chronic tophaceous gout in the sinus tarsi in both feet in a 23-year-old healthy male, with extensive bony erosions mimicking pigmented villonodular synovitis and synovial sarcoma. We discuss the clinical presentation, distinguishing radiologic characteristics, surgical procedures, and outcome regarding this unique presentation.