Cutaneous Mycobacterium avium-intracellulare infection masquerading as sarcoidosis

Mycobacterium avium-intracellulare (MAC) infection may have different skin manifestations, including cutaneous granulomas. Granulomatous skin reactions have distinct morphologic and histopathologic appearances. We present the case of an adolescent male with cutaneous MAC, misdiagnosed as sarcoidosis after initial biopsy results, demonstrated preservation of reticulin fibers and absence of organisms within granulomas. Sarcoidal granulomas often stain positive for reticulin fibers, which could be used to distinguish them from the infectious kind. This case should alert clinicians to the fact that the presence or quantity of intact reticular fibers may not be a reliable tool to differentiate between a sarcoidal and an infectious granuloma. Our case also highlights the diagnostic challenge of cutaneous MAC infection.