Gouty tophus at the Achilles tendon
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X-ray: Dorsal to the Achilles tendon, there is a blurred, hyperdens soft-tissue swelling which is suspicious of a urate salt deposit due to its density.
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MRI: T1-weighted imaging revealed a well-circumscribed, hypointense lesion partially involving the Achilles tendon with evidence of surrounding edema. On T2-weighted sequences, the lesion exhibited heterogeneous hyperintensity, consistent with soft tissue inflammation. Post-contrast imaging demonstrated mild, peripheral enhancement.
The diagnosis is confirmed intraoperatively. After opening the tumor, the urate deposit appears as a gypsum-like mass.
When using dual-energy CT (not applied here), dense intra-lesional material (high attenuation values) would have been detected, and the "urate-specific" color map would have proved the presence of monosodium urate deposits.
Gout is a systemic metabolic disorder characterized by hyperuricemia and recurrent episodes of acute arthritis. Chronic hyperuricemia leads to the deposition of monosodium urate crystals in soft tissues, including tendons, ligaments, and joints, forming tophi. While gout most commonly affects peripheral joints such as the first metatarsophalangeal joint, chronic tophaceous gout can manifest in less common locations like the Achilles tendon due to mechanical stress and local microtrauma, which may predispose it to crystal deposition. Tophi in tendons disrupt the structural integrity of collagen fibers, leading to chronic inflammation and degenerative changes.
Radiology play a pivotal role in distinguishing gouty tophi from other tendon masses, including xanthomas, tumors, and calcific tendinitis. From a clinical perspective, early recognition of tophaceous involvement in tendons is essential to guide treatment that include urate-lowering therapy to reduce serum uric acid levels and prevent further tophus formation. Surgical excision may be warranted in cases where tophi cause significant functional impairment.
