A bone marrow aspirate smear from a febrile HIV-infected farmer from Assam (CD4 count 55 cells/uL) stained with Giemsa shows macrophages packed with small intracellular yeasts. The yeasts divide by binary fission and show a single central transverse septum, with no narrow-based budding. Which organism is responsible?
- A Talaromyces (Penicillium) marneffei ✓
- B Histoplasma capsulatum
- C Leishmania donovani amastigotes
- D Trypanosoma cruzi amastigotes
Correct answer: A. Talaromyces (Penicillium) marneffei
Explanation
In tissue, Talaromyces marneffei is the only dimorphic pathogenic fungus that divides by fission, producing elongated yeast cells with a clearly visible central transverse septum on Giemsa stain. Histoplasma yeasts are similar in size but reproduce by narrow-based budding and lack the septum. Leishmania amastigotes contain a kinetoplast alongside the nucleus and do not show a fungal transverse septum, and Trypanosoma cruzi amastigotes are intracellular in cardiac muscle rather than marrow macrophages with this morphology.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.