Atypical Mycobacterial Infections
Cary Chisholm, MD
Key Facts
Clinical Issues
Tender nodules, abscesses, plaques, or ulcers
May be solitary or multiple
Erythema
M. marinum (swimming pool granuloma, fish tank granuloma)
May have history of swimming pool exposure or cleaning fish tank
M. ulcerans (Buruli ulcer, Bairnsdale ulcer)
Recent travel history to Africa
M. avium intracellulare
History of immunosuppression, most commonly HIV/AIDS
Microscopic Pathology
Hyperplastic epidermis ± ulceration
Diffuse mixed infiltrate
Granulomas ± caseation
Mycobacterial organisms identified
 Atypical mycobacterial infection over the dorsal hand presented as an indurated pink nodule  in this patient. The culture was positive for Mycobacterium marinum. |
 Some atypical mycobacterial infections have a diffuse mixed inflammatory infiltrate with associated necrosis. (Courtesy S. Billings, MD.) |
TERMINOLOGY
Definitions
Infections with Mycobacterium spp. other than M. leprae and M. tuberculosis
CLINICAL ISSUES
Epidemiology
Age
Affects any age group
Gender
No gender predilection
Ethnicity
No specific ethnic predilection
More common in developing countries and immunosuppressed
Site
Can occur anywhere after bacterial contamination
Presentation
Tender nodules, abscesses, plaques, or ulcers
May be solitary or multiple
May be superficial, deep, or both
Erythema
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