Mycobacterium marinum infection simulating interstitial granuloma annulare: a report of two cases.

We report two cases of Mycobacterium marinum infection that histologically simulated interstitial granuloma annulare (GA). In one case, an infectious etiology was not suspected in histologic sections, but a tissue culture performed during the patient's clinic visit identified M. marinum, and a subsequent Fite stain revealed mycobacteria. Interstitial granulomatous dermatitis is a rare presentation for cutaneous nontuberculous mycobacteria and has yet to be attributed specifically to M. marinum. In both immunocompetent and immunosuppressed patients, infection with M. marinum should be considered in lesions histologically resembling interstitial GA, particularly when there is clinical suspicion for an infectious process.