Bone tumours: hereditary multiple exostoses: 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 · Bone tumours: hereditary multiple exostoses

Sample item

A boy has multiple bony lumps near the knees and wrists, shortening of the forearm and a father with the same findings. Biopsy of one lump shows a cartilage cap. Which genes are usually affected?

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

The answer and the reasoning

C. EXT1 and EXT2

Hereditary multiple exostoses is an autosomal dominant condition caused by mutations in EXT1 or EXT2, which are involved in heparan sulphate synthesis. Multiple osteochondromas cause deformity and growth disturbance, and there is a small risk of malignant change to chondrosarcoma. Rapid growth or pain in adults warrants investigation.

Option by option

  • A. FGFR3

    FGFR3 mutations cause achondroplasia.

  • B. RB1 and TP53

    RB1 and TP53 are associated with osteosarcoma risk.

  • C. EXT1 and EXT2 (correct)

    Correct. EXT1 and EXT2 mutations cause multiple osteochondromas.

  • D. COL1A1 and COL1A2

    COL1A1 and COL1A2 mutations cause osteogenesis imperfecta.

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, EXT1 and EXT2. Hereditary multiple exostoses is an autosomal dominant condition caused by mutations in EXT1 or EXT2, which are involved in heparan sulphate synthesis.

Why is "FGFR3" not the answer?

FGFR3 mutations cause achondroplasia.

Why is "RB1 and TP53" not the answer?

RB1 and TP53 are associated with osteosarcoma risk.

Why is "COL1A1 and COL1A2" not the answer?

COL1A1 and COL1A2 mutations cause osteogenesis imperfecta.

What concept does this question test?

It tests Bone tumours: hereditary multiple exostoses in Orthopaedics. Multiple osteochondromas cause deformity and growth disturbance, and there is a small risk of malignant change to chondrosarcoma. Rapid growth or pain in adults warrants investigation.

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 Bone tumours: hereditary multiple exostoses?

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.