A 55-year-old female rancher presents to the emergency department complaining of an unusual skin reaction. She reports that approximately one week prior, she developed a painless, enlarging papule on her forearm which subsequently ulcerated and formed a distinctive black center. Four days ago, after seeking initial medical advice, she was started on an antimicrobial regimen. Today, despite using sun protection, she developed a widespread blistering erythematous rash on her exposed upper extremities and shoulders after only brief sun exposure while performing farm duties. Her medical history includes poorly controlled type 2 diabetes mellitus, for which she takes metformin and glyburide, and a 30-pack-year smoking history. She denies alcohol or illicit drug use. On presentation, her temperature is 37.2°C, blood pressure is 130/75 mmHg, pulse is 72/min, and respirations are 14/min. Physical examination reveals a large, non-tender, necrotic ulcer with surrounding erythema and edema on her right forearm. Additionally, there is a diffuse, intensely erythematous rash with multiple bullae and vesicles predominantly on the arms and upper chest, consistent with a severe sunburn. Given the patient's presentation, what is the most appropriate next step in management and what is the underlying cause of her current dermatological finding?

A 42-year-old rancher presents to an outpatient clinic with a 3-day history of a distinctive skin lesion on his left forearm. He recounts sustaining several abrasions while working outdoors with livestock approximately 10 days prior. Initially, he observed an asymptomatic, raised papule at the site of injury, which progressively evolved into a fluid-filled blister. Over the last 24 hours, the blister ruptured, revealing a central necrotic area that rapidly darkened to a black eschar, surrounded by significant non-pitting edema. He denies fever, chills, or systemic symptoms. His past medical history is unremarkable, and he occasionally consumes alcohol. Given the high suspicion for a specific bacterial infection, oral antibiotic therapy was initiated with doxycycline. Less than a week later, he returns to the clinic, now complaining of a painful, erythematous, and blistering rash primarily affecting his face, neck, and the dorsal aspects of both forearms. He states he has continued his outdoor work daily. His temperature is 37.1°C, blood pressure is 130/70 mmHg, pulse is 72/min, respirations are 16/min, and oxygen saturation is 98% on room air. Examination of the new rash reveals well-demarcated erythema with scattered vesicles and bullae on sun-exposed areas. What is the most likely diagnosis for this patient's new symptoms and what is the most appropriate initial management strategy?