Under the Sea: Superficial Skin Infection With an Atypical Cause

Traumatic abrasions on human extremities as a result of direct contact with sea, lake, river, or aquarium animals or from traumatic injuries sustained in seawater may develop into solitary or linear granulomatous lesions. One of the more common microbial etiologies for such infections is Mycobacterium marinum. An astute pediatrician, family physician, or nurse practitioner should have a high index of suspicion and obtain specific cultures to support the growth of Mycobacterium species. Mycobacterium marinum infections will not respond to antibiotics typically chosen to treat simple skin and soft tissue infections. Rather, M. marinum infections are best treated by prolonged antimicrobial treatment regimens for 3 to 6 months and, in some cases, may require polypharmacologic therapy. We present the case of a 6-year-old girl who suffered a traumatic abrasion on her right ankle in seawater. For 10 days, the skin infection morphed from cellulitis, papules, pustules, and eventually into sporotrichoid linear granuloma. After several failed antibiotic trials, M. marinum was eventually identified from the depth of her lesions. The patient improved after a 3-month course of clarithromycin. This case report is the first to include pictures demonstrating the clinical progression and resolution of M. marinum infection.