A 42-year-old woman from Tamil Nadu presents with a single well-demarcated hypopigmented patch on her left forearm with complete loss of sensation and absent sweating over the lesion. On examination, the ulnar nerve on the affected side is markedly thickened and tender. Slit-skin smear from the lesion is negative for acid-fast bacilli. Skin biopsy shows epithelioid granulomas with Langhans giant cells and sparse bacilli. She has no systemic symptoms or other skin lesions. What is the most appropriate next step in management?

Explanation

## Management of Tuberculoid Leprosy ### Diagnosis: Paucibacillary Tuberculoid Leprosy **Key Point:** This patient has tuberculoid leprosy, a paucibacillary form. The diagnosis is based on: - Single well-demarcated lesion with clear sensory loss - Negative slit-skin smear (BI = 0) - Histology showing epithelioid granulomas with sparse bacilli - Early, severe asymmetric nerve involvement (thickened, tender ulnar nerve) ### WHO MDT Classification & Treatment Duration | Classification | Bacillary Load | Lesion Count | Slit-Skin Smear | **MDT Regimen** | **Duration** | |---|---|---|---|---|---| | **Paucibacillary (PB)** | Low | ≤5 | Negative | Rifampicin + Dapsone + Ofloxacin | **6 months** | | **Multibacillary (MB)** | High | >5 | Positive | Rifampicin + Dapsone + Clofazimine | **12 months** | **High-Yield:** Tuberculoid and borderline tuberculoid leprosy are **paucibacillary** and treated for **6 months**. Lepromatous and borderline lepromatous are **multibacillary** and treated for **12 months**. ### Standard MDT for Paucibacillary Leprosy **Mnemonic: RDO (Paucibacillary)** — **R**ifampicin + **D**apsone + **O**floxacin 1. **Rifampicin** 600 mg monthly (supervised) + daily unsupervised 2. **Dapsone** 100 mg daily 3. **Ofloxacin** 400 mg monthly (supervised) + daily unsupervised **Duration:** 6 monthly supervised doses + daily self-administered therapy ### Management of Nerve Involvement **Clinical Pearl:** Early nerve thickening and tenderness (as in this case) warrant: - Prednisolone 0.5–1 mg/kg/day for 12 weeks, then taper (for **Type 1 reversal reaction** prevention) - Regular nerve palpation and sensory/motor testing - Surgical decompression if signs of compression neuropathy develop ### Why Lepromin Test Is NOT Indicated Here **Key Point:** The lepromin test (Mitsuda test) is a **diagnostic aid in borderline cases**, not a treatment guide. In this case: - Diagnosis is already established (tuberculoid leprosy) - Lepromin would be strongly positive (>5 mm at 4 weeks) but does not change treatment - Treatment should begin immediately to prevent nerve damage ### Flowchart: MDT Selection ```mermaid flowchart TD A[Leprosy diagnosed]:::outcome --> B{Slit-skin smear positive?}:::decision B -->|Yes| C[Multibacillary leprosy]:::outcome B -->|No| D[Paucibacillary leprosy]:::outcome C --> E[MDT-MB: RDC for 12 months]:::action D --> F[MDT-PB: RDO for 6 months]:::action F --> G[Monitor for Type 1 reversal]:::action E --> H[Monitor for Type 2 erythema nodosum leprosum]:::action ``` [cite:Park 26e Ch 8; WHO Guidelines on Leprosy]