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Type 1 reversal reaction in leprosy — DTM&H MCQ

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HardTropical Bacterial InfectionsType 1 reversal reaction in leprosyDTM&H

A 38-year-old man in Madagascar presents with multiple hypopigmented anaesthetic patches over his trunk and limbs, bilateral thickened greater auricular nerves, and nasal stuffiness. Slit-skin smears show a bacteriological index of 3+. He also has tender erythematous plaques that have appeared acutely on top of existing lesions, with a new left-sided foot drop. What reaction is he experiencing?

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Correct answer: A — Type 1 reversal reaction

Acute inflammation of existing skin lesions with new nerve damage (foot drop from common peroneal nerve involvement) in borderline leprosy is a type 1 reversal reaction. This is a delayed-type hypersensitivity reaction representing an upgrade in cell-mediated immunity. Treatment: high-dose prednisolone (tapered over months) to prevent irreversible nerve damage. Leprosy MDT must be continued. ENL (type 2) presents with new tender nodules, not inflammation of existing patches.

Reference: WHO Leprosy Guidelines; Manson's Tropical Diseases