Mycobacterium marinum, the causative agent of fish tank or swimming pool granuloma, is an atypical mycobacterial skin infection often contracted from contaminated fish tanks, swimming pools, and ocean and lake water. It is found in both fresh- and saltwater environments. Minor trauma is a predisposing factor. Aquarium enthusiasts and fish and seafood market workers are usually not aware of the risk of infection. Because of occupational risks (eg, fisherman), men are more commonly affected than women.
The typical skin lesion consists of a pustule or nodule and develops on an extremity 2-3 weeks after exposure. Nodules may ulcerate, suppurate, and spread via lymphangitic spread (about 25% of cases). In more severe infections, deeper manifestations such as tenosynovitis, arthritis, bursitis, or osteomyelitis may be seen. In immunosuppressed patients, disease can disseminate to the lungs or other systems; bacteremia is rare.
In general, the infection is usually mild and self-limited, and lesions may heal over a period of 1-2 years if left untreated, although treatment is recommended.
Related topics: Mycobacterium avium-intracellulare, Mycobacterium kansasii, Mycobacterium fortuitum, Mycobacterium chelonae, Mycobacterium scrofulaceum, Mycobacterium tuberculosis, and Atypical mycobacterial infections
Mycobacterium marinum infection in Adult
See also in: Cellulitis DDxAlerts and Notices
Important News & Links
Synopsis
Codes
ICD10CM:
A31.9 – Mycobacterial infection, unspecified
SNOMEDCT:
373438001 – Infection due to Mycobacterium marinum
A31.9 – Mycobacterial infection, unspecified
SNOMEDCT:
373438001 – Infection due to Mycobacterium marinum
Look For
Subscription Required
Diagnostic Pearls
Subscription Required
Differential Diagnosis & Pitfalls
- Other infections such as sporotrichosis, blastomycosis, coccidioidomycosis, nocardiosis, tularemia, cutaneous tuberculosis, cutaneous leishmaniasis, and actinomycosis may have a similar lymphangitic spread from cutaneous inoculation. Exposure and travel history are key for diagnosis.
- Isolated lesions may mimic other cutaneous mycobacterial infections or granulomatous disease.
- Sarcoidosis rarely ulcerates or spreads along lymphatics.
- Cellulitis has a background of erythema and a more rapid onset and spread.
- Mycetoma
- Cutaneous lymphoma may have associated fevers and weight loss.
- Sarcoma may have associated fevers and weight loss.
- Bacterial abscess has an acute onset.
- Pyoderma gangrenosum bleeds easily and appears vascular.
- Vasculitis does not usually have an exophytic growth pattern.
- Superficial thrombophlebitis
- Granuloma annulare rarely ulcerates.
- Hypertrophic lichen planus is highly pruritic and usually located on the shins.
- Foreign body reaction, especially to sea urchin spines or barnacles given the possibility of shared clinical history.
- Cutaneous anthrax
- Majocchi granuloma
- Bacillary angiomatosis can be seen in human immunodeficiency virus (HIV)- / AIDS-infected patients with low CD4 counts or patients who are otherwise immunocompromised.
- Kaposi sarcoma is a consideration in patients with HIV / AIDS.
Best Tests
Subscription Required
Management Pearls
Subscription Required
Therapy
Subscription Required
References
Subscription Required
Last Reviewed:10/15/2019
Last Updated:07/17/2023
Last Updated:07/17/2023
Mycobacterium marinum infection in Adult
See also in: Cellulitis DDx