A 85-year-old woman has large blistering lesions on the abdomen and thighs that come and go without therapy (See Figure below) Nikolsky sign is negative. Which of the following is the most likely diagnosis?

Bullous pemphigoid is most common in the elderly, and the disease often starts with urticaria-like and pruritic erythematous lesions, before classic blisters occur. The blisters arise from inflamed and normal skin, unlike in pemphigus where they arise from normal skin. As well, unlike pemphigus, mucosal lesions are minimal or absent. There are antibodies to skin basement membrane, but unlike pemphigus, antibody levels do not correlate with disease activity.