Immunodeficiency: chronic granulomatous disease: practice question

A Pathology 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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Pathology · Immunodeficiency: chronic granulomatous disease

Sample item

A 3-year-old boy has recurrent liver and lung abscesses caused by Staphylococcus aureus and Aspergillus, and biopsy shows granulomas. Which investigation best demonstrates the underlying defect?

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

The answer and the reasoning

C. Dihydrorhodamine flow cytometry showing absent neutrophil oxidative burst

Chronic granulomatous disease results from NADPH oxidase defects, so phagocytes cannot generate superoxide and hydrogen peroxide for killing. Catalase-positive organisms such as Staphylococcus aureus, Aspergillus and Burkholderia are particularly dangerous because they destroy their own peroxide. Dihydrorhodamine flow cytometry, or the nitroblue tetrazolium test, shows failure of the oxidative burst.

Option by option

  • A. Flow cytometry for CD18 expression on neutrophils

    CD18 flow cytometry is used for leukocyte adhesion deficiency type 1.

  • B. Total haemolytic complement (CH50) assay

    CH50 screens for classical complement pathway deficiencies, which do not cause this picture.

  • C. Dihydrorhodamine flow cytometry showing absent neutrophil oxidative burst (correct)

    Correct. Absent oxidative burst on dihydrorhodamine testing confirms chronic granulomatous disease.

  • D. Serum immunoglobulin levels

    Immunoglobulins are typically normal in chronic granulomatous disease.

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 Pathology question

What is the answer to this Pathology question?

The best answer is C, Dihydrorhodamine flow cytometry showing absent neutrophil oxidative burst. Chronic granulomatous disease results from NADPH oxidase defects, so phagocytes cannot generate superoxide and hydrogen peroxide for killing.

Why is "Flow cytometry for CD18 expression on neutrophils" not the answer?

CD18 flow cytometry is used for leukocyte adhesion deficiency type 1.

Why is "Total haemolytic complement (CH50) assay" not the answer?

CH50 screens for classical complement pathway deficiencies, which do not cause this picture.

Why is "Serum immunoglobulin levels" not the answer?

Immunoglobulins are typically normal in chronic granulomatous disease.

What concept does this question test?

It tests Immunodeficiency: chronic granulomatous disease in Pathology. Catalase-positive organisms such as Staphylococcus aureus, Aspergillus and Burkholderia are particularly dangerous because they destroy their own peroxide. Dihydrorhodamine flow cytometry, or the nitroblue tetrazolium test, shows failure of the oxidative burst.

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 Immunodeficiency: chronic granulomatous disease?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.