Sphingolipidoses: Krabbe disease: practice question

A Biochemistry 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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Biochemistry · Sphingolipidoses: Krabbe disease

Sample item

A 5-month-old infant is irritable, with episodes of unexplained crying, spasticity, loss of head control, optic atrophy and peripheral neuropathy. MRI shows demyelination and biopsy reveals multinucleated globoid cells. Which metabolite accumulates, and what is the enzyme defect?

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

The answer and the reasoning

B. Galactosylceramide and psychosine, from galactocerebrosidase deficiency

Krabbe disease (globoid cell leukodystrophy) is due to galactocerebrosidase deficiency. Toxic psychosine (galactosylsphingosine) destroys oligodendrocytes, causing demyelination in the central and peripheral nervous system. Globoid cells are macrophages engorged with galactosylceramide.

Option by option

  • A. GM1 ganglioside, from beta-galactosidase deficiency

    Beta-galactosidase deficiency causes GM1 gangliosidosis with coarse features and organomegaly.

  • B. Galactosylceramide and psychosine, from galactocerebrosidase deficiency (correct)

    Galactocerebrosidase deficiency with psychosine toxicity explains the demyelination and globoid cells.

  • C. Glucocerebroside, from glucocerebrosidase deficiency

    Glucocerebrosidase deficiency causes Gaucher disease with Gaucher cells and organomegaly.

  • D. Sulfatide, from arylsulfatase A deficiency

    Arylsulfatase A deficiency causes metachromatic leukodystrophy, with sulfatide storage and later onset gait problems.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Galactosylceramide and psychosine, from galactocerebrosidase deficiency. Krabbe disease (globoid cell leukodystrophy) is due to galactocerebrosidase deficiency.

Why is "GM1 ganglioside, from beta-galactosidase deficiency" not the answer?

Beta-galactosidase deficiency causes GM1 gangliosidosis with coarse features and organomegaly.

Why is "Glucocerebroside, from glucocerebrosidase deficiency" not the answer?

Glucocerebrosidase deficiency causes Gaucher disease with Gaucher cells and organomegaly.

Why is "Sulfatide, from arylsulfatase A deficiency" not the answer?

Arylsulfatase A deficiency causes metachromatic leukodystrophy, with sulfatide storage and later onset gait problems.

What concept does this question test?

It tests Sphingolipidoses: Krabbe disease in Biochemistry. Toxic psychosine (galactosylsphingosine) destroys oligodendrocytes, causing demyelination in the central and peripheral nervous system. Globoid cells are macrophages engorged with galactosylceramide.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Sphingolipidoses: Krabbe disease?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.