Nodular post-kala-azar dermal leishmaniasis: a distinct histopathological entity.

Post-kala-azar dermal leishmaniasis (PKDL) is an infrequently occurring sequel to treated visceral leishmaniasis. Diagnosis, particularly in non-endemic areas, is difficult because the clinical appearances may be subtle and simulate lepromatous leprosy. The histopathology of the condition has been a neglected subject. Nodular lesions constitute one of the large variety of lesions that can be seen in PKDL. This paper describes the histopathology of such lesions in 26 patients seen over a period of approximately 8 years in a non-endemic setting. All the biopsies had strikingly similar light microscopic features with characteristic findings: a dense lymphohistiocytic infiltrate beneath an atrophic epidermis, pronounced follicular plugging, vascular hyalinization and collagen changes and negative Fite stain. These allow a definite diagnosis of PKDL even in the absence of demonstrable Leishman-Donovan (L-D) bodies.