Musculoskeletal imaging: achondroplasia: practice question

A Radiology 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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Radiology · Musculoskeletal imaging: achondroplasia

Sample item

A child with rhizomelic limb shortening and macrocephaly has a pelvic radiograph with small squared iliac wings and flat acetabular roofs, and a lumbar spine in which the interpedicular distance narrows from L1 to L5. Which diagnosis fits best?

ARicketsBOsteogenesis imperfectaCAchondroplasiaDCongenital hypothyroidism

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

The answer and the reasoning

C. Achondroplasia

In achondroplasia the interpedicular distance decreases down the lumbar spine, the iliac wings are squared, and the acetabular roofs are flat, with a champagne-glass pelvic inlet. The narrow canal predisposes to spinal stenosis.

Option by option

A. Rickets
Rickets shows metaphyseal widening and cupping with poor mineralisation.
B. Osteogenesis imperfecta
Osteogenesis imperfecta causes osteopenia, fractures and wormian bones, not caudal canal narrowing.
C. Achondroplasia (correct)
Correct. Squared iliac wings, flat acetabular roofs and lumbar interpedicular narrowing characterise achondroplasia.
D. Congenital hypothyroidism
Congenital hypothyroidism shows delayed bone age and epiphyseal dysgenesis, not interpedicular narrowing.

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.

Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is C, Achondroplasia. In achondroplasia the interpedicular distance decreases down the lumbar spine, the iliac wings are squared, and the acetabular roofs are flat, with a champagne-glass pelvic inlet.

Why is "Rickets" not the answer?

Rickets shows metaphyseal widening and cupping with poor mineralisation.

Why is "Osteogenesis imperfecta" not the answer?

Osteogenesis imperfecta causes osteopenia, fractures and wormian bones, not caudal canal narrowing.

Why is "Congenital hypothyroidism" not the answer?

Congenital hypothyroidism shows delayed bone age and epiphyseal dysgenesis, not interpedicular narrowing.

What concept does this question test?

It tests Musculoskeletal imaging: achondroplasia in Radiology. The narrow canal predisposes to spinal stenosis.

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 Musculoskeletal imaging: achondroplasia?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology 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.