Mycobacterium marinum Infection in a 61-Year-Old Man

July 11, 2013

A biopsy revealed non-caseating granulomata, and culture revealed Mycobacterium marinum. This patient had a fish tank at home, and used his right hand to perform maintenance.



A 61-year-old male physician complained about a solitary, slightly painful lesion on the hand.

Key point: A single, linear erythematous and indurated plaque was present on the dorsum of the right hand. Further questioning revealed that the patient had a fish tank at his home; the patient often submerged his right hand in the water to perform maintenance. A biopsy revealed non-caseating granulomata, and culture revealed Mycobacterium marinum.

Treatment: The patient was given oral clarithromycin (500 mg orally every 12 hours) along with thermotherapy. The lesion resolved in about 3 months.

Note: Larger or deeper lesions, or those that demonstrate sporotrichoid spread, are most often treated with double antibiotic therapy, rather than with antibiotic monotherapy. Doxycycline, minocycline, or rifampin can be combined with clarithromycin.