Paucibacillary leprosy — DTM&H MCQ

Correct answer: E — Rifampicin and dapsone for 6 months

The correct answer is E, rifampicin and dapsone for 6 months. This patient has a single hypopigmented, anaesthetic patch, a thickened ulnar nerve, and negative slit-skin smears, which is the classic presentation of paucibacillary (tuberculoid) leprosy: few skin lesions, a single enlarged nerve, and a low bacillary load undetectable on smear. WHO multidrug therapy for paucibacillary disease is rifampicin 600 mg once monthly (supervised) plus dapsone 100 mg daily for a fixed duration of 6 months. This shorter, two-drug regimen is sufficient because the bacterial burden is low and the immune response is strong, so clofazimine and the longer 12-month course are not required. Why the other options are wrong: B. Rifampicin, dapsone, and clofazimine for 12 months: this is the WHO multidrug regimen for multibacillary leprosy, appropriate for patients with multiple lesions, multiple nerve involvement, or smear-positive disease, not this smear-negative paucibacillary case. D. Dapsone monotherapy for 24 months: dapsone monotherapy was the pre-MDT era approach and is now abandoned due to high relapse rates and the emergence of dapsone-resistant Mycobacterium leprae. C. Isoniazid, rifampicin, pyrazinamide, and ethambutol for 6 months: this is standard anti-tuberculous therapy, irrelevant to leprosy which is caused by a different mycobacterium with a distinct treatment protocol. A. Clofazimine monotherapy for 12 months: clofazimine is never used as monotherapy for leprosy; it is only ever combined with rifampicin and dapsone as part of multidrug therapy to prevent resistance. Key point: classify leprosy by lesion and nerve count and smear status; paucibacillary disease (fewer than 5 lesions, one nerve, smear negative) gets rifampicin plus dapsone for 6 months, while multibacillary disease needs the added clofazimine for 12 months.

Reference: UK Health Security Agency, Memorandum on Leprosy 2023, gov.uk publications: leprosy-memorandum, https://www.gov.uk/government/publications/leprosy-memorandum/memorandum-on-leprosy-2023