A chronic and relatively benign autoimmune disease, usually of the elderly, characterized by recurrent sub-epithelial blistering which persists for several days. Different subtypes are recognized: bullous pemphigoid is an autoimmune disease characterized by blisters on the skin and occasionally the oral cavity; cictricial pemphigoid affects the conjunctiva as well as the oral mucosa. Patients present with bullae (blisters) which burst to leave ulcers. Mucous membrane pemphigoid affects the oral cavity and other mucous membranes with limited skin involvement. The disease is caused by autoantibodies that react with a component of the basement membrane, resulting in separation. It is treated with corticosteroids or immunosuppressant drugs.