From Puncture to Pathology—Chronic Hand Swelling Unmasked as Atypical Mycobacterial Tenosynovitis: A Case Report

CASE REPORTTo date, fewer than 100 cases of NTM tenosynovitis involving the hand have been documented globally, with very few mimicking tenosynovial giant cell tumors (TSGCTs).This case adds to the limited pool of literature and emphasizes the diagnostic confusion it may cause in clinical practice.We present a rare granulomatous tenosynovitis masquerading as a TSGCT, highlighting diagnostic challenges and functional surgical management. IntroductIonGranulomatous inflammation is a distinct histopathological response, typically arising from chronic infections or foreign bodies. 1 While this type of inflammation is well-recognized in pulmonary and lymphatic systems, its presence in musculoskeletal structures is relatively uncommon.2 Among various causes, mycobacterial infections-both tuberculous and nontuberculous-are prominent contributors, though often underdiagnosed due to nonspecific clinical features and a chronic course.3 Nontuberculous mycobacteria (NTM), such as Mycobacterium marinum, M. kansasii, and M. haemophilum, are known to cause soft tissue infections through direct inoculation, especially in individuals with frequent exposure to aquatic environments or repeated local trauma.3,4 The "fish-tank granuloma" condition represents a welldescribed manifestation of M. marinum infections.These pathogens commonly affect the hand and wrist and typically present as tenosynovitis.However, due to their chronic and indolent progression, they are frequently mistaken for benign tumors, such as giant cell tumors of the tendon sheath (GCTTS).4 The diagnosis is often challenging and delayed.A high index of suspicion is required, especially in treatment-resistant or atypical chronic hand swellings.MRI provides detailed insights into soft tissue structures and the extent of involvement, while histopathological and microbiological evaluations are definitive.5