Papulosquamous disorders: verrucous epidermal naevus and mosaicism: 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.

Try it

Dermatology · Papulosquamous disorders: verrucous epidermal naevus and mosaicism

Sample item

A 3-year-old has linear brown warty plaques, S-shaped on the trunk and V-shaped on the back, present since infancy. Which concept best explains this distribution?

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

The answer and the reasoning

A. Cutaneous mosaicism following the lines of Blaschko

Epidermal naevi arise from post-zygotic mutations in a clone of cells, such as FGFR3 or PIK3CA, and the clone's migration during embryogenesis produces the lines of Blaschko, with S-shapes on the trunk, V-shapes on the back and linear streaks on the limbs. Extensive lesions may be part of an epidermal naevus syndrome.

Option by option

  • A. Cutaneous mosaicism following the lines of Blaschko (correct)

    Correct. Lines of Blaschko reflect the embryonic pattern of mosaic cell clones.

  • B. Lymphatic spread of a skin infection

    Lymphatic spread of infection is not congenital and does not give a warty plaque from infancy.

  • C. Koebner phenomenon at sites of trauma

    Koebner phenomenon needs trauma to previously normal skin and is not congenital.

  • D. Dermatomal distribution of a sensory nerve

    Dermatomes follow nerve supply and are typical of herpes zoster, not congenital naevi.

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.

More Dermatology questions

Questions about this Dermatology question

What is the answer to this Dermatology question?

The best answer is A, Cutaneous mosaicism following the lines of Blaschko. Epidermal naevi arise from post-zygotic mutations in a clone of cells, such as FGFR3 or PIK3CA, and the clone's migration during embryogenesis produces the lines of Blaschko, with S-shapes on the trunk, V-shapes on the back and linear streaks on the limbs.

Why is "Lymphatic spread of a skin infection" not the answer?

Lymphatic spread of infection is not congenital and does not give a warty plaque from infancy.

Why is "Koebner phenomenon at sites of trauma" not the answer?

Koebner phenomenon needs trauma to previously normal skin and is not congenital.

Why is "Dermatomal distribution of a sensory nerve" not the answer?

Dermatomes follow nerve supply and are typical of herpes zoster, not congenital naevi.

What concept does this question test?

It tests Papulosquamous disorders: verrucous epidermal naevus and mosaicism in Dermatology. Extensive lesions may be part of an epidermal naevus syndrome.

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 Papulosquamous disorders: verrucous epidermal naevus and mosaicism?

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.