Wood You Believe It? A Case of a Sporotrichosis Mimic

Mycobacterium marinum is an acid-fast bacillus. Human infection can occur when damaged skin is exposed to an aqueous environment that is contaminated by the organism. An infection with M marinum can present as painless purple nodules that spread along the lymphatics. Sporotrichosis presents similarly. We present a case of cutaneous M marinum infection in a patient from rural central Texas who developed lesions initially suspected to be sporotrichosis after she sustained a splinter wound of her right hand. Despite empirical treatment for sporotrichosis with itraconazole, the patient's condition worsened, prompting further investigation. A positive culture for M marinum altered the treatment plan. After a course of minocycline, the patient's cutaneous lesions resolved. This case highlights the diagnostic challenge of M marinum infections, which can mimic conditions such as sporotrichosis. M marinum is an incredibly slow-growing organism in culture and requires a high degree of foresight for accurate diagnosis. Clinicians should consider M marinum in the differential diagnosis for patients with apparent sporotrichosis lesions, particularly those with a history of appropriate environmental exposure, even in regions distant from bodies of water or occupations not routinely in contact with aquatic organisms.