Aquarium granuloma (also known as fish tank granuloma and swimming pool granuloma) is a rare skin condition caused by a non-tubercular mycobacterium known as Mycobacterium marinum. Skin infections with M. marinum in humans are relatively uncommon, and are usually acquired from contact with contaminated swimming pools, aquariums or infected fish. Signs and symptoms
Aquarium granuloma presents as a slow-growing, inflamed red bump (nodule or plaque) at the site of infection. It is characterized by a painful, itchy skin lesion,  and may become ulcerated or crusted. Skin changes usually appear roughly three weeks after the aquatic exposure.If this condition is acquired from an aquarium, then often the dominant hand is affected. If this condition is acquired from a swimming pool, then symptoms can also develop on trauma-prone body zones, such as the elbows, knees, feet and tip of the nose. Cause
For the infection to develop in humans, the two main factors required are exposure to contaminated water, and abrasion or injury to the skin. Hence, this infection is commonly seen in individuals who clean fish tanks, handle ornamental fish and work in wet fields.Aquatic systems with a high density of fish and warm waters appear to be conditions particularly favorable to this infectious agent, and increase the changes to contract fish tank granuloma. Poor water quality and various nutritional deficiencies are also possible contributing factors.Swimming pool granuloma can occur when there is inadequate chlorination of swimming pools. Diagnosis
Aquarium granuloma is relatively nonspecific in clinical presentation.
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