Genetic and metabolic disorders: chronic granulomatous disease: practice question

A Pediatrics 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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Pediatrics · Genetic and metabolic disorders: chronic granulomatous disease

Sample item

A 3-year-old boy has recurrent liver abscesses and lymphadenitis due to Staphylococcus aureus and Aspergillus. A nitroblue tetrazolium test does not turn blue. What is the basic defect?

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

The answer and the reasoning

D. Defective NADPH oxidase and respiratory burst

Chronic granulomatous disease is caused by NADPH oxidase defects, so phagocytes cannot generate superoxide, and catalase-positive organisms such as Staphylococcus, Aspergillus and Burkholderia survive. The NBT or dihydrorhodamine test is abnormal. Prophylaxis uses cotrimoxazole, itraconazole and interferon gamma.

Option by option

  • A. Defective lysosomal trafficking regulator

    A lysosomal trafficking defect is Chediak-Higashi syndrome.

  • B. Defective CD18 integrin on leukocytes

    CD18 deficiency causes leukocyte adhesion deficiency with delayed cord separation.

  • C. Absent B-cell tyrosine kinase

    Absent B-cell tyrosine kinase is X-linked agammaglobulinaemia.

  • D. Defective NADPH oxidase and respiratory burst (correct)

    Correct. NADPH oxidase failure abolishes the respiratory burst.

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 Pediatrics question

What is the answer to this Pediatrics question?

The best answer is D, Defective NADPH oxidase and respiratory burst. Chronic granulomatous disease is caused by NADPH oxidase defects, so phagocytes cannot generate superoxide, and catalase-positive organisms such as Staphylococcus, Aspergillus and Burkholderia survive.

Why is "Defective lysosomal trafficking regulator" not the answer?

A lysosomal trafficking defect is Chediak-Higashi syndrome.

Why is "Defective CD18 integrin on leukocytes" not the answer?

CD18 deficiency causes leukocyte adhesion deficiency with delayed cord separation.

Why is "Absent B-cell tyrosine kinase" not the answer?

Absent B-cell tyrosine kinase is X-linked agammaglobulinaemia.

What concept does this question test?

It tests Genetic and metabolic disorders: chronic granulomatous disease in Pediatrics. The NBT or dihydrorhodamine test is abnormal. Prophylaxis uses cotrimoxazole, itraconazole and interferon gamma.

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 Genetic and metabolic disorders: chronic granulomatous disease?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics 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.