Case with long-standing gout showing various ultrasonographic features caused by monosodium urate monohydrate crystal deposition

Gout, which is characterized by the deposition of monosodium urate monohydrate (MSU) in the synovial fluid and other tissues, is the most common form of inflammatory arthritis. Unlike the easily recognized acute and monoarticular gouty arthritis, advanced gout induces multiple finger joint disorders and may sometimes mimic rheumatoid arthritis (RA) or vice versa. The gold standard for gout diagnosis is the identification of MSU crystals via aspiration in the symptomatic joints or nodules; however, its feasibility and specificity may be inadequate. Recently, there have been important advances in imaging techniques, assisting in the non-invasive diagnosis of gout. Ultrasonography (US) has been known to have the ability to detect deposition of MSU crystals in patients with gout. Herein, we report an evocative case of long-standing gout with precisely detected specific US features indicating MSU crystal deposition and inflammation in multiple joints. Comprehensive US assessment included the bone, hyaline cartilage, soft tissue, subcutaneous nodules and tendon; we also discriminated gouty arthritis from RA.