Neurology: neurofibromatosis type 1: practice question

A General Medicine 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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General Medicine · Neurology: neurofibromatosis type 1

Sample item

A 12-year-old has six café-au-lait macules larger than 15 mm, axillary freckling and pigmented iris hamartomas. Which gene is mutated and how is it usually inherited?

ATSC1 on chromosome 9, autosomal dominantBNF2 on chromosome 22, autosomal dominantCNF1 on chromosome 17, autosomal dominantDVHL on chromosome 3, autosomal recessive

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

The answer and the reasoning

C. NF1 on chromosome 17, autosomal dominant

Neurofibromatosis type 1 follows autosomal dominant inheritance with variants of NF1 (neurofibromin) on chromosome 17. Features include café-au-lait macules, axillary freckling, neurofibromas and Lisch nodules. NF2 is characterised by bilateral vestibular schwannomas.

Option by option

A. TSC1 on chromosome 9, autosomal dominant
TSC1 causes tuberous sclerosis with ash-leaf macules and tubers.
B. NF2 on chromosome 22, autosomal dominant
NF2 gives bilateral vestibular schwannomas and few cutaneous signs.
C. NF1 on chromosome 17, autosomal dominant (correct)
Correct. Café-au-lait macules, freckling and Lisch nodules identify NF1 on chromosome 17.
D. VHL on chromosome 3, autosomal recessive
VHL disease is dominantly inherited and causes haemangioblastomas.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is C, NF1 on chromosome 17, autosomal dominant. Neurofibromatosis type 1 follows autosomal dominant inheritance with variants of NF1 (neurofibromin) on chromosome 17.

Why is "TSC1 on chromosome 9, autosomal dominant" not the answer?

TSC1 causes tuberous sclerosis with ash-leaf macules and tubers.

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

NF2 gives bilateral vestibular schwannomas and few cutaneous signs.

Why is "VHL on chromosome 3, autosomal recessive" not the answer?

VHL disease is dominantly inherited and causes haemangioblastomas.

What concept does this question test?

It tests Neurology: neurofibromatosis type 1 in General Medicine. Features include café-au-lait macules, axillary freckling, neurofibromas and Lisch nodules. NF2 is characterised by bilateral vestibular schwannomas.

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 Neurology: neurofibromatosis type 1?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.