An otherwise healthy 47-year-old man was admitted for an extensive bullous eruption that had developed over the previous 10 days. He was not receiving medication when the bullae began to appear, and his condition deteriorated rapidly. Erythematous patches covered almost the entire body surface. Numerous tense vesicles and flaccid bullae (Panels A and B), ranging from 1 to 5 cm in diameter and filled with clear yellow fluid, covered the patches; new lesions arose at the periphery of older ones. The chest and back had several areas of denuded skin. Large erosions in the oral cavity were noted. The patient's face, hands, and feet were also involved. On the basis of clinical examination, cutaneous biopsy (Panel C, hematoxylin and eosin), and direct immunofluorescence assay (Panel D), a diagnosis of linear IgA bullous disease was made. Linear IgA bullous disease is an autoimmune disorder consisting of subepidermal bullae caused by IgA autoantibodies directed against antigens of the basement-membrane zone of the skin and mucosa. The patient was treated with a combination of dapsone and systemic glucocorticoids, and he had a complete clinical remission within 3 weeks.