Review Question - QID 214908

A 5-year-old girl presents to her pediatrician with a 1-day history of a pruritic rash on her left thigh. Her parents says they first noticed the rash when she woke up the day before but it has gotten worse since that time. She recently started kindergarten and plays outside in the backyard in her free time. Her past medical history is significant for seasonal allergies, and her family history is significant for systemic lupus erythematosus. On physical exam, the rash shown in Figure A is seen, with a negative Nikolsky sign. Which of the following diseases shares the same underlying pathophysiological process as this patient's rash?