Genetic and metabolic disorders: leukodystrophies: 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: leukodystrophies

Sample item

An 8-year-old boy has declining school performance, visual loss, spastic gait and skin hyperpigmentation with adrenal insufficiency. Which test is raised?

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

The answer and the reasoning

A. Very long chain fatty acids (adrenoleukodystrophy)

X-linked adrenoleukodystrophy presents in boys with cognitive decline, visual and gait problems, and adrenal insufficiency, with raised VLCFA. Metachromatic leukodystrophy is due to arylsulfatase A deficiency and is autosomal recessive.

Option by option

  • A. Very long chain fatty acids (adrenoleukodystrophy) (correct)

    Correct. Raised VLCFA confirms X-ALD.

  • B. Plasma ammonia only

    Ammonia is raised in urea cycle defects.

  • C. Arylsulfatase A activity

    Arylsulfatase A deficiency characterises MLD, which lacks adrenal involvement.

  • D. Urine succinylacetone

    Succinylacetone is raised in tyrosinaemia type 1.

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 A, Very long chain fatty acids (adrenoleukodystrophy). X-linked adrenoleukodystrophy presents in boys with cognitive decline, visual and gait problems, and adrenal insufficiency, with raised VLCFA.

Why is "Plasma ammonia only" not the answer?

Ammonia is raised in urea cycle defects.

Why is "Arylsulfatase A activity" not the answer?

Arylsulfatase A deficiency characterises MLD, which lacks adrenal involvement.

Why is "Urine succinylacetone" not the answer?

Succinylacetone is raised in tyrosinaemia type 1.

What concept does this question test?

It tests Genetic and metabolic disorders: leukodystrophies in Pediatrics. Metachromatic leukodystrophy is due to arylsulfatase A deficiency and is autosomal recessive.

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: leukodystrophies?

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.