Swimming pool granuloma

Alternative names:

fishtank granuloma

Definition:

A granuloma whose infectious source was a swimming pool or salt water source.

Causes, incidence, and risk factors:

A swimming pool granuloma results when water contains an infectious organism, Mycobacterium marinum. This organism enters a traumatized area of skin and produces a localized infection called a granuloma. Swimming pool granulomas appear approximately 6-8 weeks after exposure to the organism. They appear as reddish bumps (papules) that slowly enlarge into purplish nodules. The elbows, fingers, back of the hands, and knees are the most common sites affected. The nodules may break down and ulcerate leaving an open sore.

The lesions generally disappear over a period months to more than a year. There is no evidence of systemic disease associated with M. marinum. This organism may pose a threat to immunocompromised people.