Dermatology: terra firma-forme dermatosis: 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 · Dermatology: terra firma-forme dermatosis

Sample item

A child has brown, velvety, dirt-like plaques on the neck that do not wash off with soap but disappear on a single wipe with isopropyl alcohol. What is the diagnosis?

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

The answer and the reasoning

C. Terra firma-forme dermatosis

Terra firma-forme dermatosis shows persistent dirt-like pigmented plaques that resist soap but vanish when rubbed with 70 percent isopropyl alcohol, which is both diagnostic and therapeutic. It is benign and probably results from abnormal keratinisation with melanin retention. Dermatitis neglecta responds to soap and water.

Option by option

  • A. Tinea nigra

    Tinea nigra shows brown hyphae on KOH and does not wipe off.

  • B. Acanthosis nigricans

    Acanthosis nigricans does not wipe off.

  • C. Terra firma-forme dermatosis (correct)

    Correct. Resolution with alcohol rubbing is characteristic.

  • D. Dermatitis neglecta only

    Dermatitis neglecta clears with soap and water.

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 C, Terra firma-forme dermatosis. Terra firma-forme dermatosis shows persistent dirt-like pigmented plaques that resist soap but vanish when rubbed with 70 percent isopropyl alcohol, which is both diagnostic and therapeutic.

Why is "Tinea nigra" not the answer?

Tinea nigra shows brown hyphae on KOH and does not wipe off.

Why is "Acanthosis nigricans" not the answer?

Acanthosis nigricans does not wipe off.

Why is "Dermatitis neglecta only" not the answer?

Dermatitis neglecta clears with soap and water.

What concept does this question test?

It tests Dermatology: terra firma-forme dermatosis in Dermatology. It is benign and probably results from abnormal keratinisation with melanin retention. Dermatitis neglecta responds to soap and water.

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 Dermatology: terra firma-forme dermatosis?

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.