Bullous Pemphigoid

Bullous pemphigoid (BP) is an acquired autoimmune blistering disease that occurs mainly in adults older than 60 years (it can occasionally occur in children) and is associated with neurologic disorders such as dementia, Parkinson disease, multiple sclerosis, and stroke. IgG autoantibodies target BP180, also called collagen XVII, and BP230—proteins that help anchor the epidermis to the dermis at the dermal–epidermal junction. Antibody binding activates complement and recruits inflammatory cells, including eosinophils. The resulting inflammation separates the epidermis from the dermis, creating a subepidermal blister. The location of the split explains the bedside appearance. Because the entire epidermal roof remains relatively intact, the bullae (elevated, fluid-filled blisters ≥10 mm in diameter) are usually tense rather than floppy. The surrounding inflammatory response produces marked pruritus and an urticarial or erythematous base. Itching can precede visible blisters, and non-bullous disease can present with excoriations, eczematous plaques, or urticarial lesions. BP is usually chronic, lasting months and sometimes years when relapses occur. This pattern differs from pemphigus vulgaris, in which the split is within the epidermis and blisters are typically fragile or flaccid. Prominent...