Aggregates of largely epithelioid histiocytes were observed in the superficial dermis. These granulomas were centrally located around follicles. Interstitial mononuclear cells were also present. Stains were negative for spirochetes and acid-fast bacilli. An immunoassay was also negative for human herpesvirus 8. Immunohistochemical staining for CD68 confirmed histiocytic differentiation.
Our patient had previously been diagnosed as having MAC infection, which was inadequately treated with a single agent. After her lichenoid eruption, a second blood culture was also positive for MAC. She had no evidence of infection with Mycobacterium tuberculosis; therefore, we believe that her tuberculid developed in response to the MAC infection. Her eruption resolved after the antiretroviral therapy was discontinued, and her CD4+ cell count returned to baseline. She subsequently died of overwhelming bacterial infections.