A 28-year-old woman with borderline tuberculoid leprosy on MDT for 2 months develops sudden loss of sensation in the right ulnar nerve distribution and weakness of intrinsic hand muscles. Examination shows tenderness over the ulnar nerve at the elbow. What is the most appropriate immediate next step?

## Lepra Reaction Type 1 (Reversal Reaction) with Acute Neuritis ### Clinical Presentation **Key Point:** This patient has a **Type 1 lepra reaction (reversal reaction)** affecting the ulnar nerve. Type 1 reactions are Type IV hypersensitivity reactions (cell-mediated) that occur in borderline forms of leprosy (BT, BL, BDL) and are characterized by acute inflammation of existing lesions and nerves. **Clinical Pearl:** Acute neuritis in the context of lepra reaction is a medical emergency because it can cause permanent nerve damage within hours to days. The sudden onset of motor weakness and sensory loss with nerve tenderness is classic for acute lepra neuritis. ### Differential: Type 1 vs Type 2 Lepra Reactions | Feature | Type 1 (Reversal Reaction) | Type 2 (ENL) | |---------|---------------------------|---------------| | **Immunopathology** | Type IV hypersensitivity (CMI) | Type III hypersensitivity (immune complex) | | **Leprosy type** | Borderline forms (BT, BDL, BL) | Lepromatous (LL, BL) | | **Timing** | Within 1 year of starting MDT or before treatment | 6 months to 2 years after MDT start | | **Skin findings** | Inflammation of existing lesions, new lesions | Painful nodules (erythema nodosum) | | **Systemic features** | Neuritis (common, severe) | Fever, iritis, neuritis (less common) | | **Histology** | Epithelioid cells, lymphocytes | Neutrophilic infiltration, immune complexes | | **Treatment** | Corticosteroids (first-line) | Corticosteroids ± Thalidomide | ### Management of Acute Lepra Neuritis ```mermaid flowchart TD A[Acute neuritis in lepra reaction]:::outcome --> B{Assess severity}:::decision B -->|Mild: sensory loss only, no motor deficit| C[Prednisolone 0.5 mg/kg/day]:::action B -->|Moderate-Severe: motor weakness, rapid progression| D[Prednisolone 1 mg/kg/day]:::action C --> E[Continue MDT]:::action D --> E E --> F[Taper over 12-24 weeks]:::action F --> G[Monitor for relapse]:::action B -->|Established paralysis unresponsive to steroids| H[Consider surgical decompression]:::urgent ``` ### Rationale for Immediate Corticosteroid Therapy **High-Yield:** Acute lepra neuritis is a medical emergency. Corticosteroids must be started **immediately** to suppress the inflammatory cascade and prevent irreversible nerve damage. 1. **Prednisolone 0.5–1 mg/kg/day** is the standard dose for Type 1 reactions with neuritis. 2. This patient has motor weakness (intrinsic hand muscle weakness), indicating moderate-to-severe neuritis → dose should be **1 mg/kg/day**. 3. **MDT must continue** to prevent bacillary relapse. 4. Gradual taper over 12–24 weeks reduces risk of rebound reaction. **Warning:** Delaying corticosteroid therapy by even a few days can result in permanent nerve damage and disability. ### Why Surgery Is NOT First-Line - Surgical decompression is reserved for **established paralysis that fails to respond to 4–6 weeks of high-dose corticosteroids**. - At presentation with acute neuritis, medical management is always attempted first. - Early surgery in the setting of active inflammation may worsen outcomes. ### Role of Investigations - **EMG/NCS** can document baseline nerve function but should NOT delay initiation of corticosteroids. - Clinical diagnosis of lepra neuritis is sufficient to start treatment. - EMG may be useful for prognostication and monitoring response, but not for diagnostic confirmation in this context. [cite:Park 26e Ch 6; Harrison 21e Ch 397]