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Type 1 Leprosy Reaction — SCE Infectious Diseases MCQ

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ModerateTropical & Imported InfectionsType 1 Leprosy ReactionSCE Infectious Diseases

A 30-year-old man from India develops a chronic painless ulcer on his sole with surrounding anaesthesia and a claw hand from ulnar nerve palsy. He is diagnosed with borderline tuberculoid leprosy and started on WHO MDT (Dapsone plus Rifampicin for 6 months). Three weeks into treatment, he develops sudden painful swelling of existing skin lesions and new neurological deficits (worsening claw hand). What has occurred?

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Reveal the answer and explanation

Correct answer: E — Type 1 reaction (reversal reaction) — cell-mediated immune upregulation causing acute neuritis and inflammation in skin lesions; requires urgent Prednisolone to prevent irreversible nerve damage

Type 1 (reversal) reactions in leprosy occur when cell-mediated immunity is upregulated — either during treatment or spontaneously. They cause acute inflammation in existing skin lesions (becoming erythematous and oedematous) and, critically, acute neuritis (painful nerve swelling with rapid loss of function). This is a medical emergency for the nerve — untreated acute neuritis leads to irreversible motor and sensory loss within days. Treatment: Prednisolone 40 mg/day tapered over 3–6 months. MDT should continue. Type 2 reactions (ENL) are different: systemic with tender subcutaneous nodules, fever, and uveitis — seen in multibacillary leprosy.

Reference: WHO 2024 – Leprosy; NICE CKS 2024 – Leprosy reactions