Lower Extremity Nodules After Spelunking in Mexico

Mycobacterium marinum is a non-tuberculous mycobacterium that presents as a nodular granulomatous disease. The bacillus can infect humans when broken skin is exposed to a contaminated aquatic environment. M. marinum infections are usually isolated to the skin and soft tissues and can spread in a lymphatic distribution. A 26-year-old male cut his right ankle while spelunking in Tulum, Mexico. He presented to his primary care physician three months after he sustained the laceration with a nonhealing wound on the right lateral posterior ankle. Examination of the lesion demonstrated erythematous, violaceous, and hyperpigmented indurated plaques with satellite lesions noted at the right medial, posterior, and lateral ankle. The lesion characteristics raised initial suspicion for an invasive fungal infection. Biopsy of the lesion demonstrated epidermal ulceration covered by neutrophilic serum, marked underlying dermal acute inflammation, and granulation tissue. A mild perivascular, predominantly lymphocytic infiltrate was present in the deep dermis with no evidence of granuloma. Acid-fast bacilli culture plated onto chocolate agar confirmed the species M. marinum.