## Comparison: Lepromatous vs Tuberculoid Leprosy — Treatment Duration and Drug Susceptibility ### Clinical Classification Basis Leprosy is classified into two polar forms based on **immune response, bacterial load, and clinical manifestations**. This directly determines antileprotic drug regimens. ### Key Differences in Treatment | Feature | Lepromatous Leprosy (LL) | Tuberculoid Leprosy (TT) | |---------|--------------------------|-------------------------| | **Bacterial load** | Very high (>10^6 bacilli) | Low (<100 bacilli) | | **Immune response** | Weak cell-mediated immunity | Strong cell-mediated immunity | | **MDT duration** | 12 months (paucibacillary equivalent: 6 months) | 6 months | | **Number of drugs** | Rifampicin + Dapsone + Clofazimine | Rifampicin + Dapsone | | **Relapse rate** | Higher (1–5%) if inadequately treated | Lower (<1%) | | **Drug resistance risk** | Higher due to bacterial burden | Lower | **Key Point:** Lepromatous leprosy requires **12 months of MDT** because of the enormous bacillary load and risk of relapse. Tuberculoid leprosy, with minimal bacilli and strong immunity, needs only **6 months**. ### Why Duration Matters 1. **Bacterial burden**: LL patients harbour 10^6–10^8 bacilli; TT patients have <100. Longer therapy is needed to sterilize LL lesions. 2. **Immune clearance**: In TT, the host's strong cell-mediated immunity helps eliminate residual bacilli; in LL, the immune system is deficient, requiring drugs to do all the work. 3. **Relapse prevention**: LL has a 3–5% relapse rate if MDT is shortened; TT has <1% relapse even with 6 months. **High-Yield:** The WHO MDT regimen for LL is **12 months** (Rifampicin + Dapsone + Clofazimine); for TT it is **6 months** (Rifampicin + Dapsone). This is the single most important discriminator. **Clinical Pearl:** A patient with LL who completes only 6 months of MDT has a significantly higher risk of relapse and drug-resistant disease. Always confirm the polar form before deciding treatment duration.
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