Abstract

Mycobacterium marinum is a non-tuberculous mycobacterium that presents as a nodular granulomatous disease. M. marinum infections are usually isolated to skin and soft tissues and can spread in a sporotrichoid distribution. Case Presentation: A 26-year-old male, while spelunking in Tulum, Mexico, sustained a small laceration on his right ankle. Three months after the initial injury, he presented at his PCP with a nonhealing wound on the right ankle. Examination of the lesion demonstrated erythematous to violaceous indurated papules coalescing into plaques. Biopsy H&E stain demonstrated epidermal ulceration with an associated neutrophil-rich superficial dermal infiltrate. In the deep dermis, a mild perivascular, predominantly lymphocytic infiltrate was present without evidence of granuloma formation. Fluorochrome staining was negative for acid fast bacilli, however, acid fast bacilli culture with smear using non-standardized methodology confirmed the species Mycobacterium marinum. PAS, GMS and Fite stains were negative for microorganisms. Histopathologic sections demonstrated epidermal changes, such as acanthosis, pseudoepitheliomatous hyperplasia and exocytosis. Treatment of M. marinum infection is typically prolonged, requiring months of antibiotics to attain clearance. In cases limited to superficial cutaneous infection, clarithromycin, doxycycline, minocycline or trimethoprim-sulfamethoxazole monotherapy for three months has shown efficacy. This case demonstrates a classic history, clinical presentation, and histopathology of a rare infection in the United States.

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