A healthy 11-year-old girl visited her family physician with a lesion on her right posterior thigh. The lesion was a 1-cm plaque that was tender, firm, erythematous, and indurated, with a central pustule. It had been present for 3 days; it was noticed by the patient after returning from a camping trip in southeastern Pennsylvania. The pustular area was incised, drained, and cultured, and the patient was started on cephalexin.
Two days later, the lesion did not improve, showing increased induration, erythema, and blistering. The patient went to the emergency department with an 8 cm by 6 cm coalescence of thin-walled vesicles and bullae with surrounding erythema (FIGURES 1 AND 2). A thick, honey-yellow adherent crust covered the eroded center of the lesion. The girl’s temperature was 37.1°C, and she reported no burning, pain, or pruritus. She had full range of motion of her right hip and knee, and no lymphadenopathy was detected. Her white blood cell count was normal; blood and wound cultures were taken.
FIGURE 1
Bullous eruption on the thigh
FIGURE 2
Close-up
What is the most likely diagnosis?
How would you empirically treat this condition?