What is the role of biopsy in the workup of suspected dermatologic manifestations of Mycobacterium avium-intracellulare (MAI) infection?

Updated: May 27, 2021
  • Author: Jaggi Rao, MD, FRCPC; Chief Editor: Dirk M Elston, MD  more...
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Answer

Answer

Primary cutaneous Mycobacterium avium-intracellulare (MAI, or MAC) infection is rare, but it does not necessarily mandate a workup for immunosuppression.

Biopsy should be performed for suspected dermatologic manifestations of MAI infection. Tissue samples of cutaneous lesions may be obtained for histopathologic evidence of mycobacterial infection, and staining with Ziehl-Neelsen stain may reveal acid-fast bacilli (AFB). [1]

Faruqi et al noted that a positive antineutrophil cytoplasmic antibody (ANCA) test result can coexist with MAI, complicating diagnosis. [25]

Cultures of cutaneous lesions should be performed, and polymerase chain reaction (PCR) studies of tissue may yield organism identification in 24 hours.

A 2012 report notes a 66-year-old women who developed sudden redness and swelling of her left thumb. Histology showed well-formed granulomas along with a mixed inflammation. The infiltrate was characterized by a predominance of neutrophils, and stains showed acid-fast bacilli. Culture results were negative. The pathogenic Mycobacterium has also been identified through broad-range polymerase chain reaction amplification followed by suspension array identification. [26]

18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) scanning can be used to distinguish disseminated MAI from paraneoplastic syndromes or malignant metastasis. [27]  Molecular assays might be useful in some cases. [28]

A 2020 case report described using MRI to evaluate a horseshoe abscess in order to diagnose and evaluate the extent of a hand infection. MRI data may provide initial data to consider infection with mycobacterial organisms. The MRI revealed rice bodies secondary to MAI infection. [29]


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