A 52-year-old woman presents with painful erosions on the oral mucosa and scattered flaccid blisters on the trunk and flexural areas for 3 weeks. On examination, positive Nikolsky sign is elicited on the skin. She denies any drug history. What is the most appropriate next step in management?

Explanation

## Diagnostic Confirmation Before Systemic Therapy **Key Point:** Pemphigus vulgaris diagnosis must be confirmed histologically and immunologically BEFORE initiating systemic corticosteroids, as these are high-dose, long-term therapies with significant morbidity. ### Diagnostic Workup **High-Yield:** The diagnostic triad for pemphigus vulgaris: 1. **Clinical features** — oral mucosal involvement (90%), flaccid blisters, positive Nikolsky sign 2. **Histopathology** — intraepidermal acantholysis (suprabasal in PV), intact basal layer (tombstone appearance) 3. **Direct immunofluorescence (DIF)** — intercellular IgG and C3 deposition ("chicken wire" pattern) ### Management Algorithm ```mermaid flowchart TD A[Clinical suspicion of PV]:::outcome --> B[Perform skin biopsy + DIF]:::action B --> C{Histology + DIF confirm PV?}:::decision C -->|Yes| D[Start oral prednisolone 1 mg/kg/day]:::action C -->|No| E[Reconsider diagnosis]:::action D --> F[Monitor clinical response + taper]:::action F --> G[Add steroid-sparing agent if needed]:::action ``` **Clinical Pearl:** Oral involvement is the most common site of presentation in PV (90% of cases) and is often the first manifestation. Erosions are painful and may precede skin lesions by weeks. ### Why Systemic Corticosteroids Are Essential - Flaccid blisters and positive Nikolsky sign indicate **active, disseminated disease** - Topical agents alone are insufficient for mucosal and widespread cutaneous involvement - Oral prednisolone 1 mg/kg/day is the **gold standard initial therapy** [cite:Fitzpatrick's Dermatology Ch 30] - Early intervention prevents progression and reduces morbidity **Warning:** Do NOT delay systemic therapy awaiting biopsy results if clinical suspicion is very high — but confirmatory tests MUST be obtained in parallel or immediately before starting. ### Steroid-Sparing Agents (Second-Line) | Agent | Role | Timing | |-------|------|--------| | Azathioprine | Steroid-sparing | Add after 2–4 weeks if inadequate control or steroid side effects | | Mycophenolate mofetil | Steroid-sparing | Alternative to AZA | | Rituximab | Severe/refractory | Reserved for failures of conventional therapy | **Mnemonic:** **PACED** — Prednisolone, Azathioprine, Corticosteroids, Evaluation (biopsy/DIF), Diagnosis confirmation. [cite:Harrison 21e Ch 297]