What are the histologic findings in cutaneous leishmaniasis?

Updated: Feb 18, 2020
  • Author: Craig G Stark, MD, FACP, FFTM, RCPS(Glasg), FISTM; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

Localized cutaneous leishmaniasis is characterized by irregular acanthosis, with or without epidermal ulceration, and dense dermal infiltrate of mixed inflammatory cells, particularly plasma cells, lymphocytes, and histiocytes. Early in the course of localized disease, organisms may be numerous and found readily in the cytoplasm of macrophages. As the lesion ages and as delayed-type immunity is upregulated, the infiltrate is replaced by noncaseating granulomata in which few or no organisms can be seen.

Ulcerated lesions are often secondarily infected by bacteria, in which case histologic changes may be nonspecific. Results with biopsy specimens obtained from old (>6 mo), partially treated, or low-burden infections are frequently nondiagnostic.

Diffuse cutaneous leishmaniasis occurs in individuals with poor cellular immunity to Leishmania parasites. Histologic diagnosis is straightforward in these cases. The dermis contains sheets of macrophages containing great numbers of amastigotes, with few lymphocytes or plasma cells.

Leishmaniasis recidivans is usually difficult to confirm because of the rarity of organisms and because of its histologic similarity to lupus vulgaris.

Post–kala-azar dermal leishmaniasis has a variable histology that is determined by the degree of host immunity and the parasite load. Granulomatous histology is seen with low numbers of organisms, whereas diffuse histiocytic or xanthomatous infiltrates may be seen with numerous organisms.


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