Disseminated Mycobacterium marinum infection in a hematopoietic stem cell transplant recipient

Mycobacterium marinum is a photochromogenic mycobacterium that is ubiquitous in the aquatic environment. In the general population, exposure to aquaria is the most common cause of M. marinum infection. Known as "swimmer's granuloma" or "fish tank granuloma," M. marinum is an occupational hazard for aquarium cleaners and fishermen. There are several reports in the literature of M. marinum infection in immunocompromised hosts, including those with solid organ transplants, but none in patients who have received stem cell transplants (SCTs). To our knowledge, this is a first report of disseminated M. marinum infection in an SCT recipient who continued to develop new skin lesions even after months of targeted therapy. The implications are that elderly patients who receive T-cell-depleted SCTs may be at prolonged risk for pathogens dependent on cellular immunity, and the presentation of illness with such pathogens may be more severe and widely disseminated than might otherwise be expected.