Bullous Pemphigoid

Bullous Pemphigoid

Major points

• Large, tense blisters arising on normal or erythematous skin
• Mucous membrane involvement in 10–35%
• Sites of predilection: lower abdomen, inner thighs, flexor forearms or generalized
• Bullae may have clear or hemorrhagic fluid
  

(Figures 1 and 2)

Figure 1. Bullous pemphigoid - large bullae on erythematous patches

Figure 2. Pemphigoid gestationis - in a young pregnant woman. Her child was unaffected

• Erosions tend to re-epithelialize quickly
• Nikolsky sign is negative
• New vesicles may form at the edge of old blisters
• Blisters do not tend to scar but may be hyperpigmented
• Mild to moderate pruritus
• Early lesions tend to look urticarial
• Rare in childhood
  

Pathogenesis

Bullous pemphigoid (BP) antigens are proteins in the hemidesmosomes (HDs). Autoantibody binds both inside the cell to plaques of HDs and outside cells to the extracellular section of HDs
BP antibodies are directed against both BPAg-1 (230 kDa) component and also BPAg-2 (180kDa) (also called type XVII collagen)

BP IgG can activate complement by the classical pathway causing leukocyte adherence to the basement membrane, degranulation of polymorphonuclear leukocytes and subsequent dermal–epidermal separation

Diagnosis

Histology: Subepidermal blister without necrosis, and superficial dermal infiltrate with lymphocytes, histiocytes and eosinophils
DIF: linear pattern of C3 and IgG at BMZ

Indirect immunoflourescence: 70–80% of patients will have circulating IgG which binds to stratified squamous epithelium; titers do not correlate with disease extent or activity ~50% have elevated IgE, and sometimes eosinophilia, which correlates with pruritus

Differential diagnosis

1. Bullous insect bite reactions
2. Bullous impetigo
3. Bullous erythema multiforme
4. Chronic bullous disease of childhood
   

Treatment

• Prednisone 1–2mg/kg per day until activity is suppressed. Once under control, steroids should be tapered to avoid side-effects
  
• Steroid-sparing agents can be used as an adjunct: cyclophosphamide, azathioprine, cyclosporine, methotrexate, or gold
• Localized BP can be treated with high-potency topical steroids
• Some patients respond to sulfones, tetracycline, or nicotinamide
  

Prognosis
BP may be self-limited and can last several months to many years
Prognosis is good. In adults, half of treated patients go into remission in 2.5–6 years