Genetic and metabolic disorders: Niemann-Pick 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: Niemann-Pick disease

Sample item

A 6-month-old has hepatosplenomegaly, failure to thrive and progressive loss of milestones, with a macular cherry-red spot. Which enzyme is deficient?

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

The answer and the reasoning

C. Acid sphingomyelinase

Niemann-Pick disease type A is acid sphingomyelinase deficiency, with sphingomyelin storage in the reticuloendothelial system and the brain. A cherry-red spot with hepatosplenomegaly distinguishes it from Tay-Sachs disease, which has a cherry-red spot without organomegaly. Foamy histiocytes are seen in marrow.

Option by option

  • A. Hexosaminidase A

    Hexosaminidase A deficiency is Tay-Sachs, with a cherry-red spot but no organomegaly.

  • B. Alpha-galactosidase A

    Alpha-galactosidase A deficiency is Fabry disease, presenting with pain and renal disease.

  • C. Acid sphingomyelinase (correct)

    Correct. Sphingomyelinase deficiency gives a cherry-red spot with hepatosplenomegaly.

  • D. Glucocerebrosidase

    Glucocerebrosidase deficiency is Gaucher disease, which usually has no cherry-red spot.

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 C, Acid sphingomyelinase. Niemann-Pick disease type A is acid sphingomyelinase deficiency, with sphingomyelin storage in the reticuloendothelial system and the brain.

Why is "Hexosaminidase A" not the answer?

Hexosaminidase A deficiency is Tay-Sachs, with a cherry-red spot but no organomegaly.

Why is "Alpha-galactosidase A" not the answer?

Alpha-galactosidase A deficiency is Fabry disease, presenting with pain and renal disease.

Why is "Glucocerebrosidase" not the answer?

Glucocerebrosidase deficiency is Gaucher disease, which usually has no cherry-red spot.

What concept does this question test?

It tests Genetic and metabolic disorders: Niemann-Pick disease in Pediatrics. A cherry-red spot with hepatosplenomegaly distinguishes it from Tay-Sachs disease, which has a cherry-red spot without organomegaly. Foamy histiocytes are seen in marrow.

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: Niemann-Pick 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.