Background: Diffuse cutaneous leishmaniasis (DCL) is a rare manifestation of human leishmaniasis, characterized by multiple, slowly progressive nodules or plaques without ulceration, involving almost the entire body. It has been suggested, that DCL results from a lack of cell-mediated immunity to leishmanial antigen, leading to uncontrolled parasite growth.
Methods: We have performed detailed clinical, histopathologic, and immunologic investigations in six patients with DCL. Biopsies were taken from the nodules, processed, and examined for determination of the macrophagic pattern present, based on the intensity of vacuolation and the frequency of vacuolated cells, the parasite index, and the presence of eosinophils. Immunologically, patients were evaluated by their response to intradermal skin test to PPD or leishmania antigen, determination of antileishmania antibodies by immunofluorescent assay, and lymphocyte proliferation assay.
Results: There seemed to be a negative relation between nodules and skin ulcerations, whereas the highest number of parasites were observed in patients with the greatest number of vacuolated macrophages. The delayed hypersensitivity skin test to leishmanial antigen was negative, and antileishmania IgG antibodies were positive in all patients.
Conclusions: Although all cases fulfill the criteria for being classified as DCL, they present a wide spectrum. Three cases were clearly at the unresponsive pole, and three other cases belonged to the subpolar form of DCL, exhibiting varying weak signs of antiparasite responsiveness.