Historically recognized as “swimming pool” or “fish tank” granuloma. Clinical features: Most infections occur 2 to 3 weeks after contact with contaminated water from one of these sources. The lesions are most often small violet papules on the hands and arms that may progress to shallow, crusty ulcerations and scar formation. Lesions are usually singular. However, multiple ascending lesions resembling sporotrichosis can occasionally occur. Most patients are clinically healthy with a previous local hand injury that becomes infected while cleaning a fish tank or patients may sustain scratches or puncture wounds from saltwater fish, shrimp, fins and other marine life contaminated with M. marinum. Swimming pools seem to be a risk only when non-chlorinated. Diagnosis: Diagnosis is made from culture and histologic examination of biopsy material, along with a compatible history of exposure. Treatment: No treatment of choice is recognized for M. marinum. However, successful treatmen