Sporotrichoid presentation of Mycobacterium marinum infection of the upper extremity. A case report.

BACKGROUND Mycobacterium marinum is a human opportunistic pathogen that is known to inhabit swimming pools, home aquariums, and natural bodies of salt and fresh water. Epidemic cases involving swimming pools are easily recognized, but sporadic cases are frequently misdiagnosed. OBJECTIVE A 42-year-old male presented with a 2-month history of the appearance of livid, verrucous, painless nodules on his right upper extremity. He had cleaned an aquarium with tropical fish for the past 2 years. METHODS A histopathological examination suggested a granulomatous inflammation. After incubation on Löwenstein-Jensen medium, Mycobacterium marinum was identified using biochemical methods and the PCR technique. RESULTS Systemic therapy with rifampicin, ethambutol, and clarithromycin over a period of 6 months led to complete resolution of the skin lesions with some residual scars. CONCLUSION Knowledge of this condition is very important to avoid unnecessary diagnostic procedures and improper treatment.