Glycogen storage disorders: Andersen disease: practice question

A Biochemistry 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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Biochemistry · Glycogen storage disorders: Andersen disease

Sample item

An infant with failure to thrive develops hepatosplenomegaly and progressive cirrhosis with portal hypertension. Liver biopsy shows PAS-positive, diastase-resistant material, and the glycogen has very long outer chains with few branch points. Which enzyme is deficient?

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

The answer and the reasoning

B. Glycogen branching enzyme (alpha-1,4 to alpha-1,6 transglucosylase)

Type IV glycogenosis (Andersen disease) is due to branching enzyme deficiency. Poorly branched, insoluble glycogen resembling amylopectin accumulates and provokes a foreign-body reaction, causing cirrhosis. Death in early childhood is common without liver transplantation.

Option by option

  • A. Muscle glycogen phosphorylase

    Muscle phosphorylase deficiency spares the liver and causes exertional cramps.

  • B. Glycogen branching enzyme (alpha-1,4 to alpha-1,6 transglucosylase) (correct)

    Without branching, glycogen forms long, poorly soluble chains that injure hepatocytes and cause cirrhosis.

  • C. Glucose-6-phosphatase

    Glucose-6-phosphatase deficiency causes hypoglycaemia and hepatomegaly with normal glycogen structure.

  • D. Glycogen debranching enzyme

    Debranching enzyme deficiency gives short outer branches (limit dextrin) and a milder liver course.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Glycogen branching enzyme (alpha-1,4 to alpha-1,6 transglucosylase). Type IV glycogenosis (Andersen disease) is due to branching enzyme deficiency.

Why is "Muscle glycogen phosphorylase" not the answer?

Muscle phosphorylase deficiency spares the liver and causes exertional cramps.

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

Glucose-6-phosphatase deficiency causes hypoglycaemia and hepatomegaly with normal glycogen structure.

Why is "Glycogen debranching enzyme" not the answer?

Debranching enzyme deficiency gives short outer branches (limit dextrin) and a milder liver course.

What concept does this question test?

It tests Glycogen storage disorders: Andersen disease in Biochemistry. Poorly branched, insoluble glycogen resembling amylopectin accumulates and provokes a foreign-body reaction, causing cirrhosis. Death in early childhood is common without liver transplantation.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Glycogen storage disorders: Andersen disease?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.