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 shows acid-fast bacilli (AFB) 1+. He is HIV-negative and has no systemic symptoms. What is the most appropriate next step in management?

Explanation

## Classification and Immediate Management of Early Leprosy **Key Point:** A single lesion with loss of sensation and low AFB load (1+) indicates **paucibacillary (PB) leprosy**, most likely indeterminate or tuberculoid leprosy. Clinical classification takes precedence over bacteriological index for treatment initiation. ### Diagnostic Criteria for PB vs MB Leprosy | Feature | Paucibacillary (PB) | Multibacillary (MB) | |---------|-------------------|--------------------| | **Number of lesions** | ≤5 | >5 | | **Slit-skin smear** | Negative or 1–2+ | 3–6+ | | **Nerve involvement** | 1 nerve trunk | >1 nerve trunk | | **MDT duration** | 6 months | 12 months | | **Infectivity** | Low | High | **High-Yield:** The WHO classification is based on **clinical assessment first**, then confirmed by bacteriology. A single lesion with sensory loss = indeterminate or TT leprosy = **PB classification**. ### Next Step Algorithm ```mermaid flowchart TD A[Single hypopigmented lesion + sensory loss]:::outcome --> B{AFB load?}:::decision B -->|Negative or 1-2+| C[Paucibacillary leprosy]:::outcome B -->|3-6+| D[Multibacillary leprosy]:::outcome C --> E[Palpate peripheral nerves]:::action D --> F[Palpate peripheral nerves]:::action E --> G[Start MDT-PB: Rifampicin + Dapsone + Clofazimine for 6 months]:::action F --> H[Start MDT-MB: Rifampicin + Dapsone + Clofazimine for 12 months]:::action ``` **Clinical Pearl:** Indeterminate leprosy (earliest form) has a single lesion, minimal sensory loss, and negative or scanty AFB. It should be treated as PB to prevent progression to tuberculoid or borderline forms. **Mnemonic: PB-5 Rule** — Paucibacillary = ≤5 lesions, ≤1 nerve involved, negative/low AFB. ### Why This Patient Gets MDT-PB 1. **Single lesion** = meets PB criterion (≤5 lesions) 2. **AFB 1+** = low bacillary load (PB range) 3. **Sensory loss present** = confirms neural involvement (indeterminate or TT) 4. **No systemic signs** = not borderline or LL form **Tip:** Do not wait for repeat smears or biopsies in a resource-limited setting. Clinical diagnosis + one slit-skin smear is sufficient to initiate MDT-PB. Early treatment prevents disability and reduces transmission.