Genetic and metabolic disorders: organic acidaemia: 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: organic acidaemia

Sample item

A previously well neonate on day 4 has poor feeding, lethargy and tachypnoea, with high anion gap metabolic acidosis, ketonuria and hyperammonaemia. Which group of disorders is most likely?

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

The answer and the reasoning

B. Organic acidaemias such as methylmalonic or propionic acidaemia

Organic acidaemias cause neonatal ketoacidosis with a high anion gap, hyperammonaemia and sometimes neutropenia. Urea cycle defects show hyperammonaemia with respiratory alkalosis and no ketosis.

Option by option

  • A. Pyloric stenosis

    Pyloric stenosis causes hypochloraemic alkalosis.

  • B. Organic acidaemias such as methylmalonic or propionic acidaemia (correct)

    Correct. Ketosis with high anion gap acidosis points to organic acidaemia.

  • C. Congenital adrenal hyperplasia

    CAH presents with salt loss and hyperkalaemia.

  • D. Urea cycle defect with respiratory acidosis

    Urea cycle defects cause respiratory alkalosis and no ketosis.

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 B, Organic acidaemias such as methylmalonic or propionic acidaemia. Organic acidaemias cause neonatal ketoacidosis with a high anion gap, hyperammonaemia and sometimes neutropenia.

Why is "Pyloric stenosis" not the answer?

Pyloric stenosis causes hypochloraemic alkalosis.

Why is "Congenital adrenal hyperplasia" not the answer?

CAH presents with salt loss and hyperkalaemia.

Why is "Urea cycle defect with respiratory acidosis" not the answer?

Urea cycle defects cause respiratory alkalosis and no ketosis.

What concept does this question test?

It tests Genetic and metabolic disorders: organic acidaemia in Pediatrics. Urea cycle defects show hyperammonaemia with respiratory alkalosis and no ketosis.

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: organic acidaemia?

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.