Abstract

Mycobacterium marinum is a non-tuberculous mycobacterium, causing infections ranging from cutaneous lesions to disseminated disease. M. marinum infection is uncommon and can be challenging to diagnose. Here, we report a chronic M. marinum infection with associated id reaction. A 56-year-old female presented with a right wrist lesion which developed three years prior, having only short-term relief with topical steroids. On exam, the lesion was a 3.5 cm x 2.5 cm erythematous plaque with central crusting. A punch biopsy showed acute and chronic granulomatous dermatitis, suggestive of folliculitis with negative PAS, AFB, and fite stains. Intralesional steroid injection was given, with partial response. Six months later, a repeat biopsy was performed which showed necrobiotic granulomatous dermatitis with negative PAS, AFB, and Giemsa stains. A tissue culture was also sent and grew M. marinum. Upon further questioning, the patient endorsed cleaning a fish tank prior to the initial lesion’s appearance. The patient thereafter developed multiple subcutaneous nodules proximal to the initial lesion and on the left thigh and ankle. The lesions on the lower extremity were felt to represent an id reaction and were not biopsied. Id reactions are not uncommon in Mycobacterial infections. To further rule out systemic infection, a PET scan was performed, which did not show increased uptake outside of the right wrist. The patient was started on appropriate multi-agent antibiotic therapy and has shown significant clinical improvement over 6 weeks. The diagnosis of cutaneous M. marinum infection requires clinicopathologic correlation as well as corresponding tissue culture results.