Lysosomal storage: mucopolysaccharidoses: 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.

Try it

Biochemistry · Lysosomal storage: mucopolysaccharidoses

Sample item

A 4-year-old boy has coarse facies, hepatosplenomegaly, joint stiffness, aggressive behaviour and hearing loss. Slit-lamp examination shows clear corneas. His maternal uncle had similar features. Urine shows raised dermatan sulfate and heparan sulfate. Which enzyme is deficient?

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

The answer and the reasoning

B. Iduronate sulfatase

Hunter syndrome (mucopolysaccharidosis II) is the X-linked recessive deficiency of iduronate sulfatase, so dermatan and heparan sulfate accumulate. It resembles Hurler syndrome but corneal clouding is absent, and the X-linked pattern with an affected maternal uncle points to Hunter syndrome.

Option by option

  • A. Alpha-L-iduronidase

    Alpha-L-iduronidase deficiency causes Hurler syndrome, which is autosomal recessive with corneal clouding.

  • B. Iduronate sulfatase (correct)

    Correct. X-linked inheritance, clear corneas and raised dermatan and heparan sulfate fit iduronate sulfatase deficiency.

  • C. Hexosaminidase A

    Hexosaminidase A deficiency causes Tay-Sachs disease with GM2 ganglioside storage and no coarse facies.

  • D. Glucocerebrosidase

    Glucocerebrosidase deficiency causes Gaucher disease, which does not raise urinary glycosaminoglycans.

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.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Iduronate sulfatase. Hunter syndrome (mucopolysaccharidosis II) is the X-linked recessive deficiency of iduronate sulfatase, so dermatan and heparan sulfate accumulate.

Why is "Alpha-L-iduronidase" not the answer?

Alpha-L-iduronidase deficiency causes Hurler syndrome, which is autosomal recessive with corneal clouding.

Why is "Hexosaminidase A" not the answer?

Hexosaminidase A deficiency causes Tay-Sachs disease with GM2 ganglioside storage and no coarse facies.

Why is "Glucocerebrosidase" not the answer?

Glucocerebrosidase deficiency causes Gaucher disease, which does not raise urinary glycosaminoglycans.

What concept does this question test?

It tests Lysosomal storage: mucopolysaccharidoses in Biochemistry. It resembles Hurler syndrome but corneal clouding is absent, and the X-linked pattern with an affected maternal uncle points to Hunter syndrome.

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 Lysosomal storage: mucopolysaccharidoses?

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.