Polymorphic Clinical and Pathological Presentation of Nontuberculous Mycobacteria: A Case Series

Background Nontuberculous mycobacteria (NTM) are a group of mycobacteria widely distributed in the environment. They may cause cutaneous infections in immunocompromised and immunocompetent hosts. Clinical presentations can be significantly heterogeneous and are not species‐specific; moreover, histological features can vary, probably depending on host immune response. On this basis, NTM infections can represent diagnostic challenges for dermatologists. Culture is the current gold standard for diagnosis; however, false positive and false negative cases are not rare. Objective To describe a few clinical cases to demonstrate the NTM‐related heterogeneous clinical and histological patterns, showing the importance of a multidisciplinary approach with different specialists (e.g., dermatologists, pathologists, and microbiologists). Methods All cases of cutaneous NTM infections evaluated at the Dermatology Unit of the University Hospital of Sassari between 2010 and 2025 were retrospectively reviewed, and a subset of cases with particularly distinctive clinical and histopathological features was selected for detailed analysis. Results The qualitative and quantitative roles played by the immune system can change the clinical and histological patterns of NTM infections. A more detailed analysis of other important variables involved in the pathogenesis of the NTM cutaneous infections might help to better understand the heterogeneous patterns.