Atypical mycobacterial infections

    Article Contributors: 
    Sean Klepper M.D.
    Stephen Lyle, M.D., ...

    Clinical Features:

    • Defined as infections caused by Mycobacterium species other than M. tuberculosis and M. leprae.
    • The most common organisms causing cutaneous infection are M. marinum (swimming pool granuloma), M. ulcerans (Buruli ulcer; found in Central Africa), M. avium-intracellulare (MAI; most commonly seen in patients with AIDS), M. fortuitum and M. chelonei.
    • The lesions may present as abscesses, ulcers, nodules, verrucous plaques or sinus tracts, and may be solitary or multiple.
    • Lesions may spread in a fashion that resembles that of sprotrichosis.

    Histologic Features:

    • Suppurative granulomas with or without caseation
    • The overlying epidermis may be hyperplastic or ulcerated.
    • Fibrosis and granulation tissue are often present, and may be florid.
    • Acid-fast stains may show the organisms.  The highest-yield location to them out is within microabscesses or vacuoles.
    • More sensitive methods for identifying the acid-fast bacilli are fluorescent antibodies and PCR.
    External Links:

    Cases associated with this book:

  • MAI
    Author: Stephen Lyle, M.D., Ph.D.

    Conference: Dermpedia Teaching Collection
  • Diagnosing atypical mycobacterial infection of the skin can be very difficult
    Author: Dr. Sate Hamza MD, FRCPC

    Conference: The Dermpath-l Mailing List Conference