Skin tumours: systemic mastocytosis mutation: practice question

A Dermatology 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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Dermatology · Skin tumours: systemic mastocytosis mutation

Sample item

An adult has persistent red-brown macules that become urticarial on stroking and a raised serum tryptase. Which mutation is found in most adults with systemic disease?

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

The answer and the reasoning

B. KIT D816V

Adult-onset mastocytosis is usually systemic and clonal, with an activating KIT D816V mutation in the great majority of cases. Skin lesions (urticaria pigmentosa) show Darier sign, and serum tryptase is typically raised. Paediatric disease is often limited to the skin and may resolve.

Option by option

  • A. BRAF V600E

    BRAF V600E is found in melanoma and hairy cell leukaemia, not mastocytosis.

  • B. KIT D816V (correct)

    Correct. KIT D816V is the characteristic activating mutation in adult systemic mastocytosis.

  • C. GNAQ Q209L

    GNAQ Q209L is found in blue naevi and uveal melanoma.

  • D. PTCH1 loss of function

    PTCH1 loss of function causes basal cell carcinoma in Gorlin syndrome.

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 Dermatology question

What is the answer to this Dermatology question?

The best answer is B, KIT D816V. Adult-onset mastocytosis is usually systemic and clonal, with an activating KIT D816V mutation in the great majority of cases.

Why is "BRAF V600E" not the answer?

BRAF V600E is found in melanoma and hairy cell leukaemia, not mastocytosis.

Why is "GNAQ Q209L" not the answer?

GNAQ Q209L is found in blue naevi and uveal melanoma.

Why is "PTCH1 loss of function" not the answer?

PTCH1 loss of function causes basal cell carcinoma in Gorlin syndrome.

What concept does this question test?

It tests Skin tumours: systemic mastocytosis mutation in Dermatology. Skin lesions (urticaria pigmentosa) show Darier sign, and serum tryptase is typically raised. Paediatric disease is often limited to the skin and may resolve.

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 Skin tumours: systemic mastocytosis mutation?

Learn each condition by its primary lesion, site and signature sign. Then use the flashcards and the other Dermatology 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.