Mycobacterial Skin Infections: Comparison between Histopathologic Features and Detection of Acid Fast Bacilli in Pathologic Section
Punkae Mahaisavariya MD*, Jane Manonukul MD**, Supakan Khemngern MD*, Angkana Chaiprasert MD***
Affiliation : * Department of Dermatology, Faculty of Medicine, Siriraj Hospital, Mahidol University ** Department of Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University *** Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University
Background : Detection of acid fast bacilli (AFB) in chronic granulomatous inflammation is an important
clue for mycobacterial infection.
Design : A retrospective review of 104 pathologic sections (from 1994 to 2001) of suspected cases of
mycobacterial (tuberculous and nontuberculous) skin infections to study histopathologic features and the
correlation with the presence of AFB in the section was performed.
Results : All cases showed granulomatous inflammations that can be categorized into 4 types: mixed cell,
suppurative, tuberculoid and palisading granuloma. AFB was found in 32 sections (30.77%). Ninety five
specimens from 104 specimens were simultaneously cultured. AFB positive cases yielded higher positive
cultural results, 17 from 29 cases (58.62%) compared to the AFB negative group, 23 from 66 cases,(34.85%).
Mixed cell granuloma was the most common histologic feature, but suppurative granuloma was the most
common histological feature (56.25%) in which AFB could be found, which was statistically significantly
different from other types of granuloma. Tuberculoid granuloma was more common in the AFB negative
group (20.83%) compared to the AFB positive group (9.37%) but the difference was not statistically
significant. In cases that AFB could not be found, the inflammation tended to be located in the upper half of
the dermis.
Conclusion : AFB can be more frequently detected in suppurative granuloma that might be located in any
portion of the dermis. This finding was not species specific.
Keywords : Mycobacterial skin infections, Histopathologic features and detection, Acid fast bacilli
