Recent media reports have highlighted a “startling and worrisome new link” between antiretroviral treatment and leprosy.1 Some people infected with HIV who have started such treatment in countries where leprosy is endemic have developed florid leprosy lesions in the initial months of treatment. What underlies these unusual manifestations and do they have implications for the control of leprosy?

The note of alarm is understandable—leprosy and HIV are both greatly feared diseases. The manifestations described, however, are a well recognised complication of antiretroviral treatment known as immune reconstitution disease or immune reconstitution inflammatory syndrome (IRIS).2 This presents with the manifestation (or “unmasking”) of a previously subclinical coinfection or the deterioration of an opportunistic infection that had been responding to treatment. These effects are due to antiretroviral treatment causing the rapid recovery of cell mediated immune responses, which trigger host immune responses to foreign antigen. Such reactions typically occur during the first four months of treatment—the most rapid phase of immune recovery.

The HIV pandemic has had surprisingly little effect on the epidemiology and …