Cutaneous non-tuberculous Mycobacterial infections: a clinical and histopathological study of 17 cases from Lebanon

Only a few studies characterized cutaneous non-tuberculous Mycobacterium (NTM) infections in this region of the world. Objective  The aim of this study was to describe the epidemiological, clinical and histological findings of cutaneous NTM infections in Lebanon.

Retrospective study of 17 patients (19 histological specimens) diagnosed with cutaneous NTM infections and confirmed by culture-based partial sequencing of the 16S rRNA gene at the American University of Beirut Medical Center between 2005 and 2008.

Of 17 cases, 14 were caused by Mycobacterium marinum. All patients were immunocompetent except for one. Clinically, the most common presentation was multiple sporotrichoid lesions over an extremity (8/17). Many patients had peculiar presentations including bruise-like patches, herpetiform lesions, annular ulcerated plaques, symmetrical nodules over the buttocks and locally disseminated lesions with surrounding pale halo. Almost all patients cleared their infection on either minocycline or clarithromycin monotherapies. Histologically, a dermal small vessel proliferation with mixed inflammation (granulation tissue-like changes) was identified in 58% of specimens. The most common type of granulomatous inflammation was the suppurative (47%) followed by the tuberculoid (30%), sarcoidal (11%), and palisading (5%) types. Lichenoid granulomatous dermatitis was noted in 42% of cases. Special staining highlighted mycobacteria in only two specimens.

The incidence of cutaneous NTM infections is high in our area. Many patients had peculiar clinical presentations. Our study is the second to report the common presence of granulation tissue-like changes as a good histological indicator of cutaneous NTM infections. Minocycline and clarithromycin remain the drugs of choice in our area.