Genetic and metabolic disorders: hereditary fructose intolerance: 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: hereditary fructose intolerance

Sample item

A 9-month-old starts sweetened fruit juice and sucrose-containing weaning foods. Within hours she vomits, sweats, becomes lethargic and has hypoglycaemia. Liver is enlarged and she is jaundiced. Which enzyme is deficient?

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

The answer and the reasoning

B. Aldolase B

In hereditary fructose intolerance aldolase B deficiency causes fructose-1-phosphate to accumulate after fructose or sucrose ingestion, trapping phosphate and blocking gluconeogenesis and glycogenolysis. Hypoglycaemia, vomiting and liver injury follow, and treatment is lifelong avoidance of fructose, sucrose and sorbitol. Symptoms begin when such foods are introduced at weaning.

Option by option

  • A. Fructokinase

    Fructokinase deficiency causes benign essential fructosuria without hypoglycaemia.

  • B. Aldolase B (correct)

    Correct. Aldolase B deficiency produces symptoms on fructose or sucrose exposure.

  • C. Glucose-6-phosphatase

    Glucose-6-phosphatase deficiency is von Gierke disease with fasting hypoglycaemia and lactic acidosis.

  • D. Galactose-1-phosphate uridyltransferase

    Galactose-1-phosphate uridyltransferase deficiency causes galactosaemia from milk feeds.

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, Aldolase B. In hereditary fructose intolerance aldolase B deficiency causes fructose-1-phosphate to accumulate after fructose or sucrose ingestion, trapping phosphate and blocking gluconeogenesis and glycogenolysis.

Why is "Fructokinase" not the answer?

Fructokinase deficiency causes benign essential fructosuria without hypoglycaemia.

Why is "Glucose-6-phosphatase" not the answer?

Glucose-6-phosphatase deficiency is von Gierke disease with fasting hypoglycaemia and lactic acidosis.

Why is "Galactose-1-phosphate uridyltransferase" not the answer?

Galactose-1-phosphate uridyltransferase deficiency causes galactosaemia from milk feeds.

What concept does this question test?

It tests Genetic and metabolic disorders: hereditary fructose intolerance in Pediatrics. Hypoglycaemia, vomiting and liver injury follow, and treatment is lifelong avoidance of fructose, sucrose and sorbitol. Symptoms begin when such foods are introduced at weaning.

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: hereditary fructose intolerance?

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.