Mycobacterium marinum is a free-living nontuberculous mycobacterium that is widely distributed in freshwater and seawater around the world. Granulomatous skin
infection from M. marinum in people who are exposed to fish or aquatic environments is a rare condition known as
fish tank granuloma. The
granuloma mainly occurs on the skin of the upper limb, in a few cases on the face, and rarely in the nasal cavity. We describe a case of M. marinum
infection that presented as a nasal cavity mass. A 57-year-old woman who was receiving
infliximab for
psoriatic arthritis visited our hospital with a complaint of right
nasal obstruction. A granulomatous mass with an irregular surface was found in the anterior part of the right nasal cavity. Tissue biopsy revealed granulation tissue. Since the application of
steroid ointment did not reduce the size of the mass, the
tumor was resected under
local anesthesia, and the base was cauterized. The pathological finding was an inflammatory
granuloma with negative Ziehl-Neelsen staining. The
granuloma recurred 3 months after resection. The
interferon-gamma release assay (IGRA) test was positive, and therefore, a mycobacterial tissue culture test was performed because of suspected nasal
tuberculosis, which identified M. marinum. The nasal cavity mass disappeared 2 months after the administration of
minocycline, followed by
clarithromycin, and subsequent discontinuation of
infliximab. M. marinum
infection can cause an intranasal mass. IGRA and the mycobacterial tissue culture test are useful for diagnosis. As in this case, the nasal lesion may be excised as an inflammatory nasal
granuloma, and therefore, there may be many more "hidden" cases of M. marinum
infection. If nasal granulation is present, the possibility of M. marinum
infection should be considered.