Histopathological spectrum of cutaneous tuberculosis and nontuberculous mycobacterial infections

The non-specific clinical findings and variable histopathologicalfeatures of cutaneous tuberculosis and non-tuberculous mycobacterialinfections often make it difficult to establish a diagnosis and initiateappropriate therapy. We investigated 25 patients diagnosed withmycobacterial infections of the skin in Hanyang University Hospitalbetween 2001 and 2011. Skin biopsy specimens were re-evaluated byvarious histopathological criteria and molecular studies. To identify themycobacteria, we performed staining for acid-fast bacilli and alsocompleted polymerase chain reaction analysis. The non-tuberculousmycobacterium species were identified by genetic sequencing offormalin-fixed, paraffin-embedded tissues. Immunocompromised statuswas more frequent in non-tuberculous mycobacterial infections than intuberculosis (p = 0.017) while disease duration was longer intuberculosis (p = 0.026). Microscopically, neutrophil infiltration,interstitial granuloma, small vessel proliferation and increased numbersof bacilli were found to be associated with non-tuberculousmycobacterial infections (all p < 0.05). In contrast, giant cells, plasmacells, tuberculoid granulomas and necrosis were associated withtuberculosis (all p < 0.05). There were no species-specifichistopathological findings in non-tuberculous mycobacterial infections.The significant histopathological differences between cutaneoustuberculous and non-tuberculous mycobacterial infections are helpfulin considering differential diagnoses. In addition, molecular techniquestogether with clinico-pathological findings may assist in makingaccurate diagnoses of cutaneous non-tuberculous mycobacterialinfections