A 35-year-old man from rural Maharashtra presents with a single hypopigmented macule on his left forearm with loss of sensation. Slit-skin smear examination shows no acid-fast bacilli. He is diagnosed with indeterminate leprosy. What is the drug of choice for treatment?

Explanation

## Indeterminate Leprosy: Treatment ### Disease Characteristics Indeterminate leprosy is the earliest and mildest form of Hansen's disease: - Single ill-defined hypopigmented macule - Sensory loss may or may not be present - Negative slit-skin smear (no AFB) - No nerve thickening - Classified as **paucibacillary (PB)** leprosy — specifically **single-lesion PB (SLPB)** ### WHO Classification & Treatment Regimen **Key Point:** Indeterminate leprosy (single lesion, smear-negative) is classified as **single-lesion paucibacillary leprosy** by WHO. The recommended treatment is **Dapsone monotherapy** (100 mg/day for 6 months) OR the **ROM single-dose regimen** (Rifampicin + Ofloxacin + Minocycline), depending on the national program. **High-Yield:** According to WHO guidelines and the Indian National Leprosy Eradication Programme (NLEP): - **Paucibacillary leprosy (1–5 lesions):** Rifampicin 600 mg once monthly + Dapsone 100 mg daily × 6 months (2-drug MDT) - **Single-lesion PB leprosy:** ROM single dose OR Dapsone monotherapy for 6 months - **Multibacillary leprosy (>5 lesions or smear-positive):** Rifampicin + Dapsone + **Clofazimine** × 12 months (3-drug MDT) **Clinical Pearl:** Clofazimine is **NOT** included in the paucibacillary MDT regimen. The 3-drug regimen (rifampicin + dapsone + clofazimine) is reserved for **multibacillary** leprosy. Indeterminate leprosy, being paucibacillary with a single lesion and negative smear, is treated with dapsone monotherapy (or 2-drug PB-MDT), not the 3-drug MB regimen. ### Why Not Option C (3-drug MDT)? | Regimen | Indication | |---------|-----------| | Dapsone monotherapy / 2-drug PB-MDT | Paucibacillary (1–5 lesions), smear-negative | | 3-drug MDT (R+D+C) | Multibacillary (>5 lesions or smear-positive) | | ROM single dose | Single-lesion PB leprosy | ### Mechanism of Action - **Dapsone:** Inhibits dihydropteroate synthase (competitive antagonist of PABA), bacteriostatic against *M. leprae* - **Rifampicin:** Inhibits bacterial DNA-dependent RNA polymerase; bactericidal (used monthly in PB-MDT) **Mnemonic:** **PB = 2 drugs (R+D) for 6 months; MB = 3 drugs (R+D+C) for 12 months** [cite: Park's Textbook of Preventive and Social Medicine, 26e, Ch 8; WHO Guidelines for the Diagnosis, Treatment and Prevention of Leprosy, 2018]