Genetic and metabolic disorders: Zellweger syndrome: 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: Zellweger syndrome

Sample item

A neonate has profound hypotonia, a high forehead with flat facies, a large fontanelle, hepatomegaly, seizures and punctate calcification of the patellae. Which laboratory finding is expected?

ARaised blood phenylalanineBRaised urinary organic acids with ketoacidosisCRaised blood lactate and pyruvate with a normal ratioDRaised very long chain fatty acids

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

The answer and the reasoning

D. Raised very long chain fatty acids

Zellweger syndrome is a peroxisome biogenesis disorder, so very long chain fatty acids accumulate and plasmalogens are reduced. Features are hypotonia, craniofacial dysmorphism, hepatomegaly, seizures and stippled epiphyses. Most infants die in the first year.

Option by option

A. Raised blood phenylalanine
High phenylalanine is phenylketonuria, which spares tone and the face.
B. Raised urinary organic acids with ketoacidosis
Ketoacidosis with organic aciduria occurs in organic acidaemias, which do not cause this dysmorphism.
C. Raised blood lactate and pyruvate with a normal ratio
Raised lactate suggests a mitochondrial disorder, which does not cause patellar calcification.
D. Raised very long chain fatty acids (correct)
Correct. Failure of peroxisomal oxidation raises very long chain fatty acids.

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.

Questions about this Pediatrics question

What is the answer to this Pediatrics question?

The best answer is D, Raised very long chain fatty acids. Zellweger syndrome is a peroxisome biogenesis disorder, so very long chain fatty acids accumulate and plasmalogens are reduced.

Why is "Raised blood phenylalanine" not the answer?

High phenylalanine is phenylketonuria, which spares tone and the face.

Why is "Raised urinary organic acids with ketoacidosis" not the answer?

Ketoacidosis with organic aciduria occurs in organic acidaemias, which do not cause this dysmorphism.

Why is "Raised blood lactate and pyruvate with a normal ratio" not the answer?

Raised lactate suggests a mitochondrial disorder, which does not cause patellar calcification.

What concept does this question test?

It tests Genetic and metabolic disorders: Zellweger syndrome in Pediatrics. Features are hypotonia, craniofacial dysmorphism, hepatomegaly, seizures and stippled epiphyses. Most infants die in the first year.

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: Zellweger syndrome?

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.