Skeletal dysplasias: ossification in cleidocranial dysplasia: 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 · Skeletal dysplasias: ossification in cleidocranial dysplasia

Sample item

Which bones are mainly affected in cleidocranial dysplasia, and by what ossification process do they form?

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

The answer and the reasoning

C. Clavicles and skull vault, formed by intramembranous ossification

Mutation of RUNX2 impairs osteoblast differentiation, and the bones that form largely by intramembranous ossification, namely the clavicle and the skull vault, are affected. Patients have normal or near-normal stature. This contrasts with achondroplasia, which affects endochondral ossification.

Option by option

  • A. Ribs only, by intramembranous ossification

    The ribs are not the main site of involvement.

  • B. Vertebral bodies, formed by endochondral ossification

    Vertebral bodies are not the principal sites.

  • C. Clavicles and skull vault, formed by intramembranous ossification (correct)

    Correct. Clavicles and the skull vault are the bones chiefly involved.

  • D. Long bone growth plates, formed by endochondral ossification

    Growth plate disease describes achondroplasia and similar disorders.

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, Clavicles and skull vault, formed by intramembranous ossification. Mutation of RUNX2 impairs osteoblast differentiation, and the bones that form largely by intramembranous ossification, namely the clavicle and the skull vault, are affected.

Why is "Ribs only, by intramembranous ossification" not the answer?

The ribs are not the main site of involvement.

Why is "Vertebral bodies, formed by endochondral ossification" not the answer?

Vertebral bodies are not the principal sites.

Why is "Long bone growth plates, formed by endochondral ossification" not the answer?

Growth plate disease describes achondroplasia and similar disorders.

What concept does this question test?

It tests Skeletal dysplasias: ossification in cleidocranial dysplasia in Orthopaedics. Patients have normal or near-normal stature. This contrasts with achondroplasia, which affects endochondral ossification.

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 Skeletal dysplasias: ossification in cleidocranial dysplasia?

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.