Nontuberculous mycobacteria (NTM) are human opportunistic pathogens with an environmental source of infection. The reports of cutaneous NTM infections has increased, and NTM have been regarded as important pathogens in recent years. This study aimed to identify characteristic clinical and histological features of cutaneous NTM infections. We evaluated the medical records and histopathologic slides of 7 cases of NTM infections that were confirmed by polymerase chain reaction between 2003 and 2007. The results showed that cutaneous NTM infections occurred in various aged people independent of their immune states and were associated with fish-related jobs or intramuscular medicinal injection. The main clinical feature was a painful erythematous nodule. Histopathologically, the most common findings were diffuse infiltration of mixed inflammatory cells and small vessel proliferation in the dermis (100%). Epidermal proliferation (71%) and dermal granuloma (71%) were also very common. Suppurative granuloma was found in 43% of the cases, and eosinophil infiltration was uncommon (14%). The lesions disappeared after a mean of 7 months (range, 1.5-12 months) with treatment by oral clarithromycin alone or in combination with other antimycobacterial agents. These clinical and histopathological data should assist clinicians in the diagnosis of NTM.

Hwang HW, et al. Ann Dermatol. 2024 Feb;36(1):44-52. https://doi.org/10.5021/ad.23.082