Medical genetics: cleidocranial dysplasia: practice question

A Anatomy 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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Anatomy · Medical genetics: cleidocranial dysplasia

Sample item

A child can bring both shoulders together at the midline and has absent clavicles, wide open fontanelles and delayed tooth eruption. Which gene, encoding an osteoblast transcription factor, is mutated?

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

The answer and the reasoning

B. RUNX2

Cleidocranial dysplasia is an autosomal dominant defect of intramembranous bone formation caused by RUNX2 mutation. The clavicles and skull vault ossify poorly and tooth eruption is delayed.

Option by option

  • A. COL1A1

    COL1A1 mutation causes osteogenesis imperfecta with fragile bones and blue sclerae.

  • B. RUNX2 (correct)

    Correct. RUNX2 is needed for osteoblast differentiation and intramembranous ossification.

  • C. FBN1

    FBN1 mutation causes Marfan syndrome.

  • D. FGFR3

    FGFR3 mutation causes achondroplasia, an endochondral bone disorder.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is B, RUNX2. Cleidocranial dysplasia is an autosomal dominant defect of intramembranous bone formation caused by RUNX2 mutation.

Why is "COL1A1" not the answer?

COL1A1 mutation causes osteogenesis imperfecta with fragile bones and blue sclerae.

Why is "FBN1" not the answer?

FBN1 mutation causes Marfan syndrome.

Why is "FGFR3" not the answer?

FGFR3 mutation causes achondroplasia, an endochondral bone disorder.

What concept does this question test?

It tests Medical genetics: cleidocranial dysplasia in Anatomy. The clavicles and skull vault ossify poorly and tooth eruption is delayed.

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 Medical genetics: cleidocranial dysplasia?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.