Genetic and metabolic disorders: Krabbe 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: Krabbe disease

Sample item

A 5-month-old, previously normal, becomes inconsolably irritable with episodic stiffening, loses head control and develops optic atrophy. CSF protein is raised, nerve conduction velocities are slow and MRI shows deep white matter demyelination. Which enzyme is deficient?

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

The answer and the reasoning

C. Galactocerebrosidase

Krabbe disease is a lysosomal leukodystrophy caused by galactocerebrosidase deficiency. Psychosine accumulates, oligodendrocytes die and globoid cells appear. The infant shows irritability, spasticity, optic atrophy and a demyelinating neuropathy with high CSF protein.

Option by option

  • A. Beta-glucocerebrosidase

    Beta-glucocerebrosidase deficiency causes Gaucher disease, with organomegaly, cytopenias and bone disease.

  • B. Alpha-galactosidase A

    Alpha-galactosidase A deficiency causes Fabry disease, with neuropathic pain, angiokeratomas and renal failure.

  • C. Galactocerebrosidase (correct)

    Correct. Galactocerebrosidase deficiency gives infantile irritability, spasticity, optic atrophy and a demyelinating neuropathy.

  • D. Hexosaminidase A isoenzyme

    Hexosaminidase A deficiency causes Tay-Sachs disease, with a cherry-red macula and startle, but no raised CSF protein or neuropathy.

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, Galactocerebrosidase. Krabbe disease is a lysosomal leukodystrophy caused by galactocerebrosidase deficiency.

Why is "Beta-glucocerebrosidase" not the answer?

Beta-glucocerebrosidase deficiency causes Gaucher disease, with organomegaly, cytopenias and bone disease.

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

Alpha-galactosidase A deficiency causes Fabry disease, with neuropathic pain, angiokeratomas and renal failure.

Why is "Hexosaminidase A isoenzyme" not the answer?

Hexosaminidase A deficiency causes Tay-Sachs disease, with a cherry-red macula and startle, but no raised CSF protein or neuropathy.

What concept does this question test?

It tests Genetic and metabolic disorders: Krabbe disease in Pediatrics. Psychosine accumulates, oligodendrocytes die and globoid cells appear. The infant shows irritability, spasticity, optic atrophy and a demyelinating neuropathy with high CSF protein.

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 Genetic and metabolic disorders: Krabbe 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.