A 32-year-old Indian male presents with a 5-day history of fever (39.5°C), sore throat, and malaise, followed by sudden onset of dusky macules on the trunk and face that have coalesced into flaccid blisters. Nikolsky sign is positive. Oral mucosa shows hemorrhagic erosions. Examination reveals epidermal detachment affecting approximately 22% of body surface area. The patient had started carbamazepine 3 weeks ago for newly diagnosed epilepsy. Based on the classification shown in the diagram marked **D**, which of the following best describes this patient's condition and the most appropriate immediate management?