Vesiculobullous disorders: erythropoietic protoporphyria: 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 · Vesiculobullous disorders: erythropoietic protoporphyria

Sample item

A child cries within minutes of sun exposure because of burning and stinging of the face and hands, with only mild swelling and later waxy scarring. Which enzyme is deficient?

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

The answer and the reasoning

B. Ferrochelatase

Erythropoietic protoporphyria results from ferrochelatase deficiency with accumulation of protoporphyrin, causing immediate painful phototoxicity rather than blisters. Complications include gallstones and liver disease, and sun protection and beta-carotene are used.

Option by option

  • A. Uroporphyrinogen III synthase

    Uroporphyrinogen III synthase deficiency causes congenital erythropoietic porphyria, with severe mutilating blistering.

  • B. Ferrochelatase (correct)

    Correct. Ferrochelatase deficiency causes protoporphyrin buildup and immediate pain on sun exposure.

  • C. Porphobilinogen deaminase

    Porphobilinogen deaminase deficiency causes acute intermittent porphyria without photosensitivity.

  • D. Uroporphyrinogen decarboxylase

    Uroporphyrinogen decarboxylase deficiency causes porphyria cutanea tarda, with fragile skin and blisters.

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, Ferrochelatase. Erythropoietic protoporphyria results from ferrochelatase deficiency with accumulation of protoporphyrin, causing immediate painful phototoxicity rather than blisters.

Why is "Uroporphyrinogen III synthase" not the answer?

Uroporphyrinogen III synthase deficiency causes congenital erythropoietic porphyria, with severe mutilating blistering.

Why is "Porphobilinogen deaminase" not the answer?

Porphobilinogen deaminase deficiency causes acute intermittent porphyria without photosensitivity.

Why is "Uroporphyrinogen decarboxylase" not the answer?

Uroporphyrinogen decarboxylase deficiency causes porphyria cutanea tarda, with fragile skin and blisters.

What concept does this question test?

It tests Vesiculobullous disorders: erythropoietic protoporphyria in Dermatology. Complications include gallstones and liver disease, and sun protection and beta-carotene are used.

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 Vesiculobullous disorders: erythropoietic protoporphyria?

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.