Crystal deposition disease masquerading as proliferative tenosynovitis and its associated sequelae.

Extra-articular crystalline deposition secondary to gout, and less commonly, pseudogout is a well known phenomenon. Despite this well-documented entity of extra-articular deposition, there have been few reports of infiltration of the flexor tendon sheath of the hand. Here, we present a case series of this unique occurrence, including surgical techniques, pathology, and the clinical outcomes of 5 patients. We encountered 2 cases of calcium pyrophosphate and 3 cases of uric acid deposition into the flexor tendon sheath masquerading as common tendonopathies. These include cases of carpal tunnel syndrome, nonsuppurative flexor tenosynovitis, trigger finger, and attrition rupture of the flexor tendons. Although, medical therapy is the cornerstone of treatment for diseases that result in crystal deposition, these cases emphasize the potential need for surgical therapy in the armamentarium of their management. This case series demonstrates the importance of inclusion of crystal deposition into the flexor tendon sheath in the differential diagnosis in patients that present with uncharacteristic symptomatology of common flexor tendonopathies.