Pigmentary disorders: hypomelanosis of Ito: 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: hypomelanosis of Ito

Sample item

A 2-year-old has whorled and streaky hypopigmented macules along Blaschko lines on the trunk and limbs, together with seizures and developmental delay. Which explanation best fits?

APigmentary mosaicism from genetically distinct melanocyte clonesBPost-inflammatory loss after an earlier vesicular stageCAutoimmune destruction of melanocytes by CD8 T cellsDX-linked dominant IKBKG mutation that is lethal in males

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

The answer and the reasoning

A. Pigmentary mosaicism from genetically distinct melanocyte clones

Hypomelanosis of Ito is a descriptive term for pigmentary mosaicism: streaks and whorls along Blaschko lines reflect migration of genetically different melanocyte clones, often with chromosomal mosaicism. Extracutaneous features such as seizures, intellectual disability and musculoskeletal anomalies can accompany it.

Option by option

A. Pigmentary mosaicism from genetically distinct melanocyte clones (correct)
Correct. Blaschko-line hypopigmentation with neurological features reflects pigmentary mosaicism.
B. Post-inflammatory loss after an earlier vesicular stage
No preceding blistering occurred here, so post-inflammatory change is not the mechanism.
C. Autoimmune destruction of melanocytes by CD8 T cells
Autoimmune destruction of melanocytes causes acquired vitiligo, with depigmented rather than hypopigmented patches not following Blaschko lines.
D. X-linked dominant IKBKG mutation that is lethal in males
IKBKG mutation causes incontinentia pigmenti, which passes through vesicular, verrucous and hyperpigmented stages before 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.

Questions about this Dermatology question

What is the answer to this Dermatology question?

The best answer is A, Pigmentary mosaicism from genetically distinct melanocyte clones. Hypomelanosis of Ito is a descriptive term for pigmentary mosaicism: streaks and whorls along Blaschko lines reflect migration of genetically different melanocyte clones, often with chromosomal mosaicism.

Why is "Post-inflammatory loss after an earlier vesicular stage" not the answer?

No preceding blistering occurred here, so post-inflammatory change is not the mechanism.

Why is "Autoimmune destruction of melanocytes by CD8 T cells" not the answer?

Autoimmune destruction of melanocytes causes acquired vitiligo, with depigmented rather than hypopigmented patches not following Blaschko lines.

Why is "X-linked dominant IKBKG mutation that is lethal in males" not the answer?

IKBKG mutation causes incontinentia pigmenti, which passes through vesicular, verrucous and hyperpigmented stages before hypopigmentation.

What concept does this question test?

It tests Pigmentary disorders: hypomelanosis of Ito in Dermatology. Extracutaneous features such as seizures, intellectual disability and musculoskeletal anomalies can accompany it.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: hypomelanosis of Ito?

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.