A swimming pool granuloma is a long-term (chronic) skin infection caused by the bacteria Mycobacterium marinum.

Causes

A swimming pool granuloma occurs when water containing Mycobacterium marinum bacteria enters a break in the skin. A skin infection occurs about 3 weeks later.

Risks include exposure to swimming pools, salt water aquariums, or ocean fish.

Symptoms

The main symptom is reddish bumps (papules) that slowly grow into purplish nodules.

The elbows, fingers, and back of the hands are the most common body parts affected. The knees and legs are less commonly affected.

The nodules may break down and leave an open sore. Or they may spread up the limb.

Exams and Tests

Tests to diagnose swimming pool granuloma include:

• PPD tuberculin skin test
• Skin biopsy and culture

Treatment

Antibiotics are used to treat this infection. They are chosen based on the results of the culture and skin biopsy.

You may need several months of treatment with a combination of antibiotics. Surgery may also be needed.

Outlook (Prognosis)

Swimming pool granulomas can usually be treated completely with antibiotics.

Possible Complications

Occasionally, joint or bone infections occur. The disease may be longer or more complicated in patients whose immune system is not working properly.

When to Contact a Medical Professional

Call your health care provider if you develop reddish bumps on your skin which do not clear with home treatment.

Prevention

Avoid contact with contaminated water. Wear gloves or wash thoroughly when cleaning aquariums.

Alternative Names

Aquarium granuloma; Fish tank granuloma