[Atypical mycobacteriosis of the skin]

A 60-year-old immunocompetent patient presented with painless subcutaneous nodules on the right hand and forearm that progressed over several weeks. Nodules were clinically classified as a soft tissue tumor of primarily mesenchymal origin. After extirpation of two nodules for diagnostic clarification, histology showed a chronic granulomatous inflammation of the dermis and subcutis with central eosinophilic necrosis including cell debris. Light microscopy showed no acid-fast rods, but molecular diagnostics revealed DNA of Mycobacterium haemophilum as a nontuberculoid mycobacterium (NTM). The infection was identified as the cause of the nodules based on the classic histomorphology of necrotizing-granulomatous inflammation in addition to PCR-based pathogen diagnostics. This case illustrates the clinical presence of mycobacterial infections, especially in extrapulmonary and extranodal localizations. In addition to cutaneous foci of infection, NTM infections may cause multisystem disease involving the joint system, depending on the host's immunocompetence, which can be treated with antibiotics.