A systemic, serious, and life-threatening disorder characterized by lesions in the skin and mucous membranes that may lead to necrosis. The lesions may appear anywhere in the body but they occur more commonly in the palms, soles, dorsum of the hands, and extensor surfaces. The lesions are vesicular or necrotic in the center, surrounded by an erythematous zone and occupy less than 10% of the body surfaces. The appearance of the mucocutaneous lesions is preceded by an upper respiratory tract infection. It is an immune complex hypersensitivity reaction usually caused by drugs (e.g., sulfa, phenytoin, penicillin), viruses (e.g., herpes simplex, influenza, hepatitis), and malignancies (e.g., carcinoma and lymphoma) OR A disorder characterized by less than 10% total body skin area separation of dermis. The syndrome is thought to be a hypersensitivity complex affecting the skin and the mucous membranes.