Cell injury and adaptation: lysosomal glycogen storage: 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 · Cell injury and adaptation: lysosomal glycogen storage

Sample item

A 4-month-old hypotonic infant has macroglossia and marked cardiomegaly. A muscle biopsy shows vacuolated fibres filled with PAS-positive material that is abolished by diastase. Which enzyme is deficient?

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

The answer and the reasoning

B. Lysosomal acid alpha-glucosidase

Pompe disease (glycogen storage disease type II) is a lysosomal storage disorder in which glycogen accumulates inside lysosomes because acid alpha-glucosidase is missing. The classic infantile form shows cardiomegaly, hypotonia and early death. The other glycogenoses mainly store glycogen in the cytoplasm and spare the heart in this pattern.

Option by option

  • A. Muscle glycogen phosphorylase

    Muscle phosphorylase deficiency is McArdle disease, with exercise cramps in older children and adults.

  • B. Lysosomal acid alpha-glucosidase (correct)

    Correct. Lack of acid maltase leaves glycogen trapped in lysosomes of heart and muscle.

  • C. Amylo-1,6-glucosidase (debranching enzyme)

    Debranching enzyme deficiency is Cori disease, with hepatomegaly and fasting hypoglycaemia.

  • D. Glucose-6-phosphatase

    Glucose-6-phosphatase deficiency is von Gierke disease, with hepatomegaly and hypoglycaemia rather than cardiomegaly.

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, Lysosomal acid alpha-glucosidase. Pompe disease (glycogen storage disease type II) is a lysosomal storage disorder in which glycogen accumulates inside lysosomes because acid alpha-glucosidase is missing.

Why is "Muscle glycogen phosphorylase" not the answer?

Muscle phosphorylase deficiency is McArdle disease, with exercise cramps in older children and adults.

Why is "Amylo-1,6-glucosidase (debranching enzyme)" not the answer?

Debranching enzyme deficiency is Cori disease, with hepatomegaly and fasting hypoglycaemia.

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

Glucose-6-phosphatase deficiency is von Gierke disease, with hepatomegaly and hypoglycaemia rather than cardiomegaly.

What concept does this question test?

It tests Cell injury and adaptation: lysosomal glycogen storage in Pathology. The classic infantile form shows cardiomegaly, hypotonia and early death. The other glycogenoses mainly store glycogen in the cytoplasm and spare the heart in this pattern.

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 Cell injury and adaptation: lysosomal glycogen storage?

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.