Abstract

Mycobacterium chelonae is a rapidly growing non-tuberculous ubiquitous mycobacterium that can cause localized skin and soft tissue infections. However, in immunocompromised patients, disseminated disease can occur. We present a 59-year-old man with rheumatoid arthritis on methotrexate and methylprednisolone with a several month history of large non-healing ulceration of the bilateral legs. Dermatological examination demonstrated large, irregular ulcerations with overlying fibrinous material of the bilateral legs. Additional inflamed pustular plaques and purulent nodules were also noted on the bilateral knees and thighs. A 4-mm punch biopsy revealed Gram-positive and acid-fast filamentous and beaded organisms within a granulomatous and suppurative infiltrate. The patient was initially treated with meropenem and sulfamethoxazole-trimethoprim for presumed nocardiosis with initial improvement of his lesions. However, he continued to develop new abscesses. Tissue culture ultimately revealed clarithromycin-sensitive Mycobacterium chelonae. The patient was started on clarithromycin with near resolution of his ulcerations. This case demonstrates the difficulty in distinguishing Nocardia and Mycobacterium species by morphology alone and the importance of culture identification for proper treatment.

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