Infection with Mycobacterium marinum has several different clinical presentations. Most commonly, it appears as a solitary papulonodular lesion on an extremity. A rare presentation of osteoarticular M. marinum involving multiple small joints and tenosynovitis of the hand, which was misdiagnosed as rheumatoid arthritis, is reported. The patient was initially treated for seronegative rheumatoid arthritis but failed to respond to methotrexate. Magnetic resonance imaging showed arthritis and tenosynovitis. Subsequently, synovial biopsy led to histological and microbiological diagnosis. Antimycobacterial treatment should be started promptly in such cases. The combined use of rifampicin, ethambutol, and clarithromycin appears to be effective, and debridement is indicated in patients with deep-seated infections.
Keywords: Mycobacterium marinum; Epithelioid granuloma; interferon gamma release assay; oligoarthritis; rheumatoid arthritis.
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