A 68-year-old woman presents with tense bullae on the flexural surfaces of the arms and inner thighs for 3 weeks. Histopathology shows subepidermal blister with eosinophil-rich infiltrate. Direct immunofluorescence reveals linear IgG and C3 deposits along the basement membrane zone. What is the drug of choice for initial management of this condition?

Explanation

## Diagnosis & Pathophysiology This clinical presentation is classic for **bullous pemphigoid (BP)**: - Tense, firm bullae (do not rupture easily) - Flexural distribution (inner arms, thighs, lower abdomen) - Subepidermal blister with eosinophil-rich infiltrate on histology - Linear IgG and C3 at the basement membrane zone on direct immunofluorescence BP is an autoimmune disorder targeting hemidesmosomal antigens (BP180, BP230) at the dermal–epidermal junction. ## First-Line Treatment Hierarchy | Severity | First-Line Agent | Role of Alternatives | |----------|------------------|----------------------| | Mild/localized | Potent topical corticosteroids | May suffice alone | | Moderate/generalized | **Systemic corticosteroids** | Gold standard; rapid control | | Severe/extensive | Systemic corticosteroids + steroid-sparing agent | Azathioprine, mycophenolate | | Steroid-dependent | Dapsone or azathioprine | Adjunctive, not monotherapy | ## Why Systemic Corticosteroids? **Key Point:** Systemic corticosteroids (oral prednisolone 0.5–1 mg/kg/day) are the **first-line and gold standard** for moderate-to-generalized bullous pemphigoid because they: 1. Rapidly suppress autoantibody production and T-cell–mediated immunity 2. Achieve clinical remission in 70–80% of patients within 4–8 weeks 3. Have the fastest onset of action among all agents 4. Are well-tolerated in elderly patients (the typical BP demographic) when used at appropriate doses **High-Yield:** The typical starting dose is **prednisolone 0.5–1 mg/kg/day** (e.g., 30–50 mg daily for a 60 kg patient), then taper slowly over 3–6 months once remission is achieved. **Clinical Pearl:** Topical corticosteroids alone may suffice for **very localized** disease (e.g., a few lesions on one limb), but this patient has widespread involvement (flexural surfaces bilaterally) and therefore requires systemic therapy. ## Steroid-Sparing Agents (Adjunctive Role) - **Dapsone**: Useful in steroid-dependent or steroid-resistant cases; not first-line monotherapy - **Azathioprine**: Added to corticosteroids in severe cases to allow dose reduction; slower onset (weeks to months) - **Mycophenolate mofetil**: Emerging alternative for steroid-sparing effect **Warning:** Do not use dapsone or azathioprine as monotherapy for newly diagnosed, moderate-to-generalized BP — they are too slow and lack the rapid anti-inflammatory effect needed for disease control.