Paediatric: osteopetrosis: practice question

A Orthopaedics 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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Orthopaedics · Paediatric: osteopetrosis

Sample item

A child has recurrent fractures despite very dense bones, anaemia and cranial nerve palsies. Radiographs show a bone-within-bone appearance and Erlenmeyer flask deformity. What is the underlying defect?

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

The answer and the reasoning

C. Failure of osteoclast function and bone resorption

Osteopetrosis (marble bone disease) results from defective osteoclastic bone resorption, often with carbonic anhydrase II or ClC-7 chloride channel defects. Bones are dense but brittle, and marrow obliteration causes anaemia. Bone marrow transplantation treats severe infantile forms.

Option by option

  • A. Defective type I collagen synthesis

    Defective type I collagen causes osteogenesis imperfecta.

  • B. Impaired vitamin D hydroxylation

    Impaired vitamin D hydroxylation causes rickets.

  • C. Failure of osteoclast function and bone resorption (correct)

    Correct. Failed osteoclast resorption causes osteopetrosis.

  • D. Osteoblast overactivity from fibroblast growth factor 23 excess

    FGF23 excess causes hypophosphataemic rickets.

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 Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is C, Failure of osteoclast function and bone resorption. Osteopetrosis (marble bone disease) results from defective osteoclastic bone resorption, often with carbonic anhydrase II or ClC-7 chloride channel defects.

Why is "Defective type I collagen synthesis" not the answer?

Defective type I collagen causes osteogenesis imperfecta.

Why is "Impaired vitamin D hydroxylation" not the answer?

Impaired vitamin D hydroxylation causes rickets.

Why is "Osteoblast overactivity from fibroblast growth factor 23 excess" not the answer?

FGF23 excess causes hypophosphataemic rickets.

What concept does this question test?

It tests Paediatric: osteopetrosis in Orthopaedics. Bones are dense but brittle, and marrow obliteration causes anaemia. Bone marrow transplantation treats severe infantile forms.

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 Paediatric: osteopetrosis?

Pair each fracture with its classic complication and nerve injured. Then use the flashcards and the other Orthopaedics 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.