Detection of Leishmania DNA by polymerase chain reaction in scars of treated human patients.

Leishmaniasis is an endemic disease in developing countries. The efficacy of therapy is usually evaluated through clinical parameters. To define the parasitologic cure, 20 patients were biopsied before and 1 month to 8 years after treatment. Paraffin-embedded tissue was used for DNA isolation. All patients had a positive polymerase chain reaction (PCR) result before therapy, except 1, for whom no histopathologic material was available. The causative agent was identified as belonging to the Leishmania (Viannia) subgenus by hybridization. Despite clinical healing and absence of reactivation or development of mucosal lesions, PCR was positive in scars of 16 patients (80%). The results suggest that parasites persist in the skin for many years despite treatment. Depending on specific pathogenetic features of the parasite and the immune status of the host, this phenomenon might result in mucosal lesions. Alternatively, it could have a role in the maintenance of immunologic memory in patients living in areas in which leishmaniasis is endemic.