Discoid chronic lupus erythematosus at the site of a previously healed cutaneous leishmaniasis: an example of isotopic response.

The term "isotopic response" describes the occurrence of a new skin disorder at the site of another, unrelated and already healed one. We report here the case of a 38-year-old woman who referred to us for an infiltrated, red-brownish plaque localized on her left cheek. The patient had been treated for a cutaneous leishmaniasis, confirmed by the histologic examination, localized at the same site. She was completely healed after an appropriate local and systemic treatment. She experienced the occurrence of the new plaque at the site of the previously healed cutaneous leishmaniasis three month later. Histologic examination and laboratory tests were consistent with a diagnosis of discoid cutaneous chronic lupus erythematosus. Treatment with hydroxychloroquine, topical clobetasol and topical tretinoin resulted in flattening and clearing of the lesion. Our case is the first case of isotopic response where a discoid chronic lupus erythematosus had occurred at the site of an already healed cutaneous leishmaniasis. We speculate that the activation of type-1 interferon system may be involved in the pathogenesis of our case.