Leprosy: Lucio phenomenon versus necrotic ENL: 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 · Leprosy: Lucio phenomenon versus necrotic ENL

Sample item

Which feature distinguishes Lucio phenomenon from necrotising erythema nodosum leprosum?

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

The answer and the reasoning

C. It occurs in untreated diffuse lepromatous disease, with endothelial invasion by bacilli and thrombosis

Lucio phenomenon is a necrotising vasculopathy that arises in untreated diffuse non-nodular lepromatous leprosy, with bacilli in endothelial cells and thrombosis. Necrotising ENL appears in nodular lepromatous or borderline lepromatous disease, usually during treatment, with a neutrophilic vasculitis.

Option by option

  • A. It occurs on treatment in nodular lepromatous disease with neutrophilic infiltration

    This describes necrotising ENL, an immune-complex reaction that occurs during treatment.

  • B. It is a type 1 reaction with oedema within epithelioid granulomas

    This describes a type 1 reaction, which is a delayed hypersensitivity response.

  • C. It occurs in untreated diffuse lepromatous disease, with endothelial invasion by bacilli and thrombosis (correct)

    Correct. Lucio phenomenon is a thrombotic vasculopathy of untreated diffuse lepromatous disease.

  • D. It occurs only in tuberculoid disease with a negative smear

    Lucio phenomenon does not occur in tuberculoid disease, which has few bacilli.

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, It occurs in untreated diffuse lepromatous disease, with endothelial invasion by bacilli and thrombosis. Lucio phenomenon is a necrotising vasculopathy that arises in untreated diffuse non-nodular lepromatous leprosy, with bacilli in endothelial cells and thrombosis.

Why is "It occurs on treatment in nodular lepromatous disease with neutrophil…" not the answer?

This describes necrotising ENL, an immune-complex reaction that occurs during treatment.

Why is "It is a type 1 reaction with oedema within epithelioid granulomas" not the answer?

This describes a type 1 reaction, which is a delayed hypersensitivity response.

Why is "It occurs only in tuberculoid disease with a negative smear" not the answer?

Lucio phenomenon does not occur in tuberculoid disease, which has few bacilli.

What concept does this question test?

It tests Leprosy: Lucio phenomenon versus necrotic ENL in Dermatology. Necrotising ENL appears in nodular lepromatous or borderline lepromatous disease, usually during treatment, with a neutrophilic vasculitis.

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 Leprosy: Lucio phenomenon versus necrotic ENL?

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.