Recurrent Fluctuant Mass of the Wrist and Forearm Associated with Chronic Tenosynovitis by Mycobacterium kansasii

This article presents a case of a painless fluctuant mass on the volar aspect of the wrist and forearm of an immunocompetent 45-year-old man with no history of significant underlying disease. This mass proved to be a chronic tenosynovitis associated with Mycobacterium kansasii infection. The patient, who had a history of multiple minor cuts and abrasions plus exposure to an aquatic environment, had a wide resection of the lesion and elective tenosynovectomy. Operative findings revealed a marked tenosynovitis of flexor tendons. Several rice bodies lesions were also observed along the course of the involved flexor tendons. Biopsy showed a granulomatous inflammatory reaction. Specimens of affected tissue were sent to a laboratory for solid (at 30°C and at 37°C) and liquid (at 37°C) mycobacterial culture. The initial Ziehl-Neelsen stain for acid-fast bacilli was positive. After 8 days of incubation, acid-fast bacilli were recovered. In accordance with the diagnosis of M kansasii tenosynovitis and the results of antibiotic susceptibility testing, triple therapy with rifampicin, isoniazid and clarithromycin was initiated. After 3 months of therapy, the patient experienced improvement in the swelling and is due to receive 12 months of antibiotic therapy. Despite awareness of atypical mycobacterial infections, diagnosis is frequently delayed, leading to increased morbidity. Patients with exposure to these atypical pathogens require a broadened differential to include appropriate testing and culture of specimens to obtain an accurate diagnosis.