Genetics: neurofibromatosis 1: practice question

A Pediatrics 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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Pediatrics · Genetics: neurofibromatosis 1

Sample item

A 7-year-old has six cafe-au-lait spots larger than 5 mm, axillary freckling and Lisch nodules. What is the mode of inheritance and gene?

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

The answer and the reasoning

A. Autosomal dominant, NF1 on chromosome 17

Neurofibromatosis type 1 is autosomal dominant, caused by mutations of neurofibromin on 17q11.2, with half of cases arising from new mutations. Optic glioma, neurofibromas and scoliosis are other features. NF2 has bilateral vestibular schwannomas and is linked to chromosome 22.

Option by option

  • A. Autosomal dominant, NF1 on chromosome 17 (correct)

    Correct. NF1 is autosomal dominant on chromosome 17.

  • B. X-linked recessive

    NF1 is not X-linked.

  • C. Autosomal recessive, chromosome 17

    NF1 is not autosomal recessive.

  • D. Autosomal dominant, NF2 on chromosome 22

    NF2 is associated with bilateral acoustic schwannomas.

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 Pediatrics question

What is the answer to this Pediatrics question?

The best answer is A, Autosomal dominant, NF1 on chromosome 17. Neurofibromatosis type 1 is autosomal dominant, caused by mutations of neurofibromin on 17q11.

Why is "X-linked recessive" not the answer?

NF1 is not X-linked.

Why is "Autosomal recessive, chromosome 17" not the answer?

NF1 is not autosomal recessive.

Why is "Autosomal dominant, NF2 on chromosome 22" not the answer?

NF2 is associated with bilateral acoustic schwannomas.

What concept does this question test?

It tests Genetics: neurofibromatosis 1 in Pediatrics. 2, with half of cases arising from new mutations. Optic glioma, neurofibromas and scoliosis are other features. NF2 has bilateral vestibular schwannomas and is linked to chromosome 22.

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 Genetics: neurofibromatosis 1?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics 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.