Bullous disorders: porphyria cutanea tarda: 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 · Bullous disorders: porphyria cutanea tarda

Sample item

A man with chronic alcohol use and hepatitis C has fragile skin, blisters and milia on the dorsum of the hands, with hypertrichosis on the face. Urine fluoresces coral pink under Wood's lamp. Which enzyme is deficient?

AFerrochelataseBDelta-aminolevulinic acid dehydrataseCUroporphyrinogen decarboxylaseDPorphobilinogen deaminase

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

The answer and the reasoning

C. Uroporphyrinogen decarboxylase

Porphyria cutanea tarda, the commonest porphyria, results from reduced hepatic uroporphyrinogen decarboxylase activity, aggravated by iron, alcohol, estrogens and hepatitis C. Management includes phlebotomy or low-dose hydroxychloroquine and avoiding precipitants.

Option by option

A. Ferrochelatase
Ferrochelatase deficiency causes erythropoietic protoporphyria with painful photosensitivity.
B. Delta-aminolevulinic acid dehydratase
ALA dehydratase deficiency is a rare acute porphyria.
C. Uroporphyrinogen decarboxylase (correct)
Correct. Uroporphyrinogen decarboxylase deficiency causes PCT.
D. Porphobilinogen deaminase
Porphobilinogen deaminase deficiency causes acute intermittent porphyria, which lacks skin lesions.

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 C, Uroporphyrinogen decarboxylase. Porphyria cutanea tarda, the commonest porphyria, results from reduced hepatic uroporphyrinogen decarboxylase activity, aggravated by iron, alcohol, estrogens and hepatitis C.

Why is "Ferrochelatase" not the answer?

Ferrochelatase deficiency causes erythropoietic protoporphyria with painful photosensitivity.

Why is "Delta-aminolevulinic acid dehydratase" not the answer?

ALA dehydratase deficiency is a rare acute porphyria.

Why is "Porphobilinogen deaminase" not the answer?

Porphobilinogen deaminase deficiency causes acute intermittent porphyria, which lacks skin lesions.

What concept does this question test?

It tests Bullous disorders: porphyria cutanea tarda in Dermatology. Management includes phlebotomy or low-dose hydroxychloroquine and avoiding precipitants.

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 Bullous disorders: porphyria cutanea tarda?

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.