Cutaneous non‐tuberculous mycobacterial infections: A retrospective study of 94 cases from Germany

BACKGROUND: Cutaneous non-tuberculous mycobacterial infections (NTM) remain a diagnostic and therapeutic challenge. The aim of this study was to characterize cutaneous NTM infections in Germany over a 24-year-period. PATIENTS AND METHODS: 73 patients with cutaneous NTM infections diagnosed at 17 different German University Hospitals from 2000-2011 and 21 patients treated at the Department of Dermatology of the University Hospital Cologne, from 2010-2024. Retrospective analysis of patient, demographic, clinical information, and data on different diagnostic workups and therapeutic approaches/responses. RESULTS: Together, 94 cases were analyzed (71% males, mean age 50, > 75% immunocompetent). Exposure to fish tanks was the dominant risk factor. Pathogen detection by nucleic acid amplification test and/or culture was successful in 76%. The most common pathogen was Mycobacterium (M.) marinum (> 65%), followed by M. abscessus/chelonae. Immunosuppression was associated with NTM other than M. marinum. Over 90% were treated with oral antibiotics, in more than 50% with a single antibiotic (mostly clarithromycin). The most common combination was clarithromycin plus rifampicin. The mean duration of therapy was more than 4 months. Complications, adverse events, and relapses were rare. CONCLUSIONS: Our findings highlight that there is a need for standardized diagnostic procedures- and therapeutic recommendations for cutaneous NTM infections.