Pigmentary disorders: Waardenburg syndrome: 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 · Pigmentary disorders: Waardenburg syndrome

Sample item

A newborn has a white forelock, irides of two different colours, a broad nasal root with lateral displacement of the inner canthi, and fails the hearing screen. Which gene is most often mutated?

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

The answer and the reasoning

B. PAX3

Waardenburg syndrome type 1 combines a white forelock, heterochromia iridis, dystopia canthorum and sensorineural deafness. It is caused by loss of function of PAX3, a transcription factor needed for neural crest melanocyte development. Dystopia canthorum separates type 1 from type 2.

Option by option

  • A. GNAS

    GNAS activating mutation causes McCune-Albright syndrome with café-au-lait macules and endocrine disease.

  • B. PAX3 (correct)

    Correct. PAX3 mutation causes Waardenburg syndrome type 1 with dystopia canthorum and deafness.

  • C. LYST

    LYST mutation causes Chediak-Higashi syndrome, with silvery hair, albinism and giant lysosomal granules, not deafness and dystopia canthorum.

  • D. TYR

    TYR encodes tyrosinase, and its loss causes oculocutaneous albinism with generalized hypopigmentation.

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, PAX3. Waardenburg syndrome type 1 combines a white forelock, heterochromia iridis, dystopia canthorum and sensorineural deafness.

Why is "GNAS" not the answer?

GNAS activating mutation causes McCune-Albright syndrome with café-au-lait macules and endocrine disease.

Why is "LYST" not the answer?

LYST mutation causes Chediak-Higashi syndrome, with silvery hair, albinism and giant lysosomal granules, not deafness and dystopia canthorum.

Why is "TYR" not the answer?

TYR encodes tyrosinase, and its loss causes oculocutaneous albinism with generalized hypopigmentation.

What concept does this question test?

It tests Pigmentary disorders: Waardenburg syndrome in Dermatology. It is caused by loss of function of PAX3, a transcription factor needed for neural crest melanocyte development. Dystopia canthorum separates type 1 from type 2.

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 Pigmentary disorders: Waardenburg syndrome?

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.