Bacteriology: type 1 lepra reaction: practice question

A Microbiology 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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Microbiology · Bacteriology: type 1 lepra reaction

Sample item

A patient with borderline tuberculoid leprosy starts multidrug therapy. Two months later his existing skin patches become red, swollen and tender, and he develops acute ulnar nerve tenderness with a new claw hand. Which diagnosis is most likely?

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

The answer and the reasoning

B. Reversal reaction from a rise in delayed-type hypersensitivity

The type 1 or reversal reaction occurs in borderline leprosy when cell-mediated immunity to M. leprae rises. Existing lesions become inflamed and nerves swell, so nerve function loss needs urgent steroid treatment.

Option by option

  • A. Relapse from dapsone resistance

    Relapse after only two months of treatment would not present as acute inflammation of existing lesions.

  • B. Reversal reaction from a rise in delayed-type hypersensitivity (correct)

    Correct. Inflamed old lesions with new neuritis indicate a type 1 reaction.

  • C. Erythema nodosum leprosum from immune complexes

    ENL presents with new tender nodules, fever and vasculitis in lepromatous disease.

  • D. Lucio phenomenon from diffuse lepromatous disease

    Lucio phenomenon is necrotising skin ulceration in diffuse non-nodular lepromatous leprosy.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Reversal reaction from a rise in delayed-type hypersensitivity. The type 1 or reversal reaction occurs in borderline leprosy when cell-mediated immunity to M.

Why is "Relapse from dapsone resistance" not the answer?

Relapse after only two months of treatment would not present as acute inflammation of existing lesions.

Why is "Erythema nodosum leprosum from immune complexes" not the answer?

ENL presents with new tender nodules, fever and vasculitis in lepromatous disease.

Why is "Lucio phenomenon from diffuse lepromatous disease" not the answer?

Lucio phenomenon is necrotising skin ulceration in diffuse non-nodular lepromatous leprosy.

What concept does this question test?

It tests Bacteriology: type 1 lepra reaction in Microbiology. leprae rises. Existing lesions become inflamed and nerves swell, so nerve function loss needs urgent steroid treatment.

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 Bacteriology: type 1 lepra reaction?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.