Haematology: pyruvate kinase deficiency: practice question

A Pathology 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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Pathology · Haematology: pyruvate kinase deficiency

Sample item

A 4-year-old child of consanguineous parents has chronic haemolytic anaemia since the neonatal period, splenomegaly. The G6PD assay and the smear for spherocytes are normal. Red cells are rigid and short-lived. What is the main biochemical consequence in the red cell?

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

The answer and the reasoning

B. ATP depletion that impairs membrane cation pumps

Pyruvate kinase catalyses the last step of glycolysis, which is the red cell's only source of ATP. ATP depletion damages the cation pumps, so the cells lose potassium and water and become rigid and are removed by the spleen.

Option by option

  • A. Loss of membrane skeleton linkage proteins

    Membrane skeleton protein defects cause hereditary spherocytosis, which would show spherocytes on the smear.

  • B. ATP depletion that impairs membrane cation pumps (correct)

    Correct. Loss of the final ATP-generating glycolytic step leaves the red cell energy-depleted and rigid.

  • C. Fall in NADPH that depletes glutathione

    NADPH is generated by the pentose phosphate pathway and its fall causes the G6PD deficiency picture, which was excluded.

  • D. Excess unpaired alpha chains

    Unpaired alpha chains are the problem in beta thalassaemia, not a glycolytic enzyme defect.

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 Pathology question

What is the answer to this Pathology question?

The best answer is B, ATP depletion that impairs membrane cation pumps. Pyruvate kinase catalyses the last step of glycolysis, which is the red cell's only source of ATP.

Why is "Loss of membrane skeleton linkage proteins" not the answer?

Membrane skeleton protein defects cause hereditary spherocytosis, which would show spherocytes on the smear.

Why is "Fall in NADPH that depletes glutathione" not the answer?

NADPH is generated by the pentose phosphate pathway and its fall causes the G6PD deficiency picture, which was excluded.

Why is "Excess unpaired alpha chains" not the answer?

Unpaired alpha chains are the problem in beta thalassaemia, not a glycolytic enzyme defect.

What concept does this question test?

It tests Haematology: pyruvate kinase deficiency in Pathology. ATP depletion damages the cation pumps, so the cells lose potassium and water and become rigid and are removed by the spleen.

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 Haematology: pyruvate kinase deficiency?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.