Mycology: Histoplasma capsulatum: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · Mycology: Histoplasma capsulatum

Sample item

A man who explored a bat-inhabited cave has fever, weight loss, hepatosplenomegaly and pancytopenia. A Giemsa-stained bone marrow smear shows 2 to 4 micrometre oval yeasts with a clear halo inside macrophages, with no kinetoplast. What is the most likely diagnosis?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Histoplasma capsulatum

Histoplasma capsulatum is a thermally dimorphic fungus found in soil enriched by bird and bat droppings. In tissue it appears as small budding yeasts inside macrophages, and disseminated disease mimics visceral leishmaniasis. The absence of a kinetoplast separates it from Leishmania amastigotes, and urine antigen assists diagnosis.

Option by option

  • A. Cryptococcus neoformans

    Cryptococcus is a larger extracellular encapsulated yeast and is not usually inside macrophages in marrow.

  • B. Histoplasma capsulatum (correct)

    Correct. Intramacrophage small budding yeasts and cave exposure indicate histoplasmosis.

  • C. Pneumocystis jirovecii

    Pneumocystis causes pneumonia and does not appear as marrow yeasts in macrophages.

  • D. Leishmania donovani

    Leishmania amastigotes have a nucleus and a rod-shaped kinetoplast, which is absent here.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Histoplasma capsulatum. Histoplasma capsulatum is a thermally dimorphic fungus found in soil enriched by bird and bat droppings.

Why is "Cryptococcus neoformans" not the answer?

Cryptococcus is a larger extracellular encapsulated yeast and is not usually inside macrophages in marrow.

Why is "Pneumocystis jirovecii" not the answer?

Pneumocystis causes pneumonia and does not appear as marrow yeasts in macrophages.

Why is "Leishmania donovani" not the answer?

Leishmania amastigotes have a nucleus and a rod-shaped kinetoplast, which is absent here.

What concept does this question test?

It tests Mycology: Histoplasma capsulatum in Microbiology. In tissue it appears as small budding yeasts inside macrophages, and disseminated disease mimics visceral leishmaniasis. The absence of a kinetoplast separates it from Leishmania amastigotes, and urine antigen assists diagnosis.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Mycology: Histoplasma capsulatum?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.