Bullous pemphigoid is best described as which of the following?

• A. Autoimmune blistering disease that primarily affects the elderly with subepidermal bullae and eosinophils
• B. Bacterial skin infection
• C. Allergic contact dermatitis
• D. Fungal infection

Answer: (A)

Bullous pemphigoid is an autoimmune blistering disease that targets the dermal-epidermal junction, leading to subepidermal, tense bullae. It most commonly affects older adults. The immune attack is directed against basement membrane components, especially BP180 (type XVII collagen) and BP230, which weakens adhesion at the junction and allows blisters to form just beneath the epidermis. Histologically, you see a subepidermal blister with an eosinophil-rich inflammatory infiltrate, and clinically the blisters are often very pruritic and rupture with minimal surrounding inflammation. A Nikolsky sign is typically negative, helping distinguish it from pemphigus vulgaris, which has intraepidermal splitting. This description fits bullous pemphigoid best, whereas a bacterial skin infection, allergic contact dermatitis, or a fungal infection would present with different patterns of lesions and underlying pathology.