5 Findings to differentiate Histoplasma from Leishmania Why is it important to differentiate histoplasma and leishmania in histology sections, blood and bone marrow smears? Histoplasma yeast form and leishmania donovani amastigote form are particularly difficult to distinguish. We will discuss further how to differentiate between the two; since treatments differ. It is not uncommon for someone who has worked long enough in a hematology laboratory to have encountered histoplasmosis wrongly diagnosed as leishmania or vice versa, based on a bone marrow aspiration or biopsy. Leishmania infection can mimic anything form malignancy to autoimmune diseases, yet histoplasmosis is among the top differentials. Hence caution is warranted. LOCATION Histoplasma is predominantly intracellular. Extracellular organisms are very rare. Leishmamia is intracellular as well as extracellular. 2. BACKGROUND INFLAMMATION Histoplasma has very minimal background inflammation. No neutrophils, eosinophils and plasma cells. Leishmania often shows an inflammatory background, especially dense infiltration of plasma cells, often leading to misdiagnosis. 3. PERIODIC ACID SCHIFF (PAS) POSITIVITY Histoplasma stains positive with PAS, whereas Leishmania does not stain PAS positive. 4. NUCLEUS The nucleus of leishmania donovani has a small kinetoplast near the nucleus. Kinetoplast is composed of mitochondrial DNA. (black arrow) Histoplasma has a characteristic crescent shaped nucleus.(green arrow) 5. SIZE There is a very slight variation in size. Histoplasma is 2-5 microns and Leishmania is 1- 4 microns. Though not very significant, this can be helpful at times. That’s it- hopefully the confusion is cleared. For a quick summary click below. PARIS SYSTEM FOR REPORTING URINARY CYTOLOGY MCQs by Pathology MCQs 22 Mar 2022 Breast Pathology MCQ 1 by Pathology MCQs 12 Mar 2022 CNS Pathology case based MCQs-2 by Pathology MCQs 23 Feb 2022 PARIS SYSTEM FOR REPORTING URINARY CYTOLOGY MCQs Breast Pathology MCQ 1 CNS Pathology case based MCQs-2 CNS Pathology case based MCQs-1 Central nervous system pathology MCQ 1 Liked the page? Why not leave a tip for it’s creators Share this:FacebookTelegramWhatsAppMoreLinkedInTwitterLike this:Like Loading...