Case reports: successful treatment of Mycobacterium marinum infection with minocycline after complication of disease by delayed diagnosis and systemic steroids.

Mycobacterium marinum, an aerobic, non-tuberculous, environmental mycobacterium, is the etiologic agent responsible for "fish tank granuloma." Found in aquatic environments, particularly where water is relatively still or stagnant, M. marinum produces infection in fish, as well as humans. Infection follows exposure to contaminated water and direct inoculation of the organism via breaks in the skin. The resulting primary lesion is usually a red-to-violaceous plaque or nodule, which can have an overlying crust or verrucous surface that may ulcerate and, in some cases, may be accompanied by satellite lesions and lymphangitic spread. We present an aggressive case of M. marinum infection with prominent lymph node involvement in an otherwise healthy 34-year-old woman whose course was complicated by delayed diagnosis and treatment with systemic steroids.