Bullous Pemphigoid: Pathology, Diagnosis & Treatment

Bullous pemphigoid is a chronic, autoimmune blistering skin disorder typically seen in the elderly. Though it may resemble other blistering diseases such as pemphigus vulgaris, its subepidermal blistering and relative milder severity make it a distinct and clinically significant entity.

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🧬 What is Bullous Pemphigoid?

Bullous pemphigoid is an autoimmune skin condition characterized by IgG autoantibodies directed against hemidesmosomes, the structures that anchor the basal layer of the epidermis to the basement membrane.

🔍 Pathophysiology:

• Hemidesmosomes = “glue” between basal keratinocytes and basement membrane
• Autoantibodies target BP180 (type XVII collagen) and BP230
• This causes subepidermal separation → tense bullae formation
• Inflammatory cells (eosinophils) infiltrate the skin

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🧓 Epidemiology

Factor	Detail
Age	Usually > 70 years old
Gender	Slight male predominance
Risk Factors	Sulfa drugs (e.g., furosemide, penicillamine), neurological disorders (e.g., Parkinson’s, stroke)

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🧍 Clinical Presentation

Feature	Bullous Pemphigoid
Blisters	Tense, thick-walled bullae
Location	Abdomen, flexor surfaces, groin, thighs
Oral lesions	Rare
Nikolsky sign	Negative (skin does not slough off with friction)
Pruritus	Often present before bullae form
Systemic symptoms	Rare, usually localized to skin

📸 Example:

Large, tense, non-fragile bullae over the thighs and lower abdomen of an elderly patient, sparing the mucosa.

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🔬 Histology & Diagnosis

1. Skin Biopsy:

• Shows subepidermal blistering
• Dense eosinophilic infiltrate in the dermis

2. Direct Immunofluorescence (DIF):

• Linear IgG and C3 deposition at the dermoepidermal junction
• “White linear band” along the basement membrane

3. Serologic Tests:

• ELISA detects anti-BP180 and anti-BP230 antibodies

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🔬 Bullous Pemphigoid vs. Pemphigus Vulgaris

Feature	Bullous Pemphigoid	Pemphigus Vulgaris
Target antigen	Hemidesmosomes (BP180, BP230)	Desmosomes (desmoglein 3/1)
Blister location	Subepidermal	Intraepidermal
Blister type	Tense bullae	Flaccid bullae
Oral involvement	Rare	Common
Nikolsky sign	Negative	Positive
Age	Elderly	Younger adults

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💊 Treatment

Treatment aims to suppress the immune response and manage symptoms.

First-Line Options:

Treatment	Notes
Topical corticosteroids	Effective in localized/mild cases if mucosa is spared
Systemic corticosteroids	Prednisone – for generalized, moderate-to-severe disease

Steroid-Sparing Agents:

• Tetracycline + Nicotinamide + Erythromycin (anti-inflammatory regimen)
• Azathioprine or Mycophenolate mofetil for long-term immune suppression
• Methotrexate in selected refractory cases

Severe or Refractory Cases:

• IVIG (rarely needed)
• Rituximab – reserved for resistant bullous pemphigoid

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📋 Summary Table

Key Point	Bullous Pemphigoid
Autoimmune target	Hemidesmosomes (BP180/BP230)
Histology	Subepidermal blisters with eosinophils
Immunofluorescence	Linear IgG/C3 along basement membrane
Nikolsky Sign	Negative
Oral Involvement	Rare
Treatment	Corticosteroids ± immunosuppressants