Localization of Mycobacterium avium-intracellulare within a skin lesion of bacillary angiomatosis in a patient with AIDS.

We report a 39-year-old man who had AIDS and who presented with an unusual cutaneous vascular lesion, which was clinically thought to be Kaposi's sarcoma. Histologically, the lesion was characterized by capillary proliferation and a mixed inflammatory infiltrate that included numerous histiocytes. The lesion was found to contain slender intracellular acid-fast bacilli, as well as plump extracellular Warthin-Starry-positive bacilli. The acid-fast bacilli were confirmed to be Mycobacterium avium-intracellulare by subsequent positive blood cultures for this organism. To further investigate the lesion, polymerase chain reaction DNA amplification and sequencing was performed, and the lesion was found to contain DNA sequences identical to those previously established for the agent of bacillary angiomatosis. The lesion is thought to represent a lesion of bacillary angiomatosis with secondary involvement by M. avium-intracellulare.