Review Question - QID 213228

A 12-year-old boy is brought to the emergency department by his mother for a rash. The patient had a sore throat a few days ago with symptoms initially well-controlled with lozenges. However, today he had a rash covering his body, which prompted his presentation. The mother states that she did smear an herbal remedy on the rash with no alleviation in symptoms and also gave him a single dose of amoxicillin left over from a previous infection. The patient is up to date on his vaccinations and has no past medical conditions. His temperature is 101°F (38.3°C), blood pressure is 102/68 mmHg, pulse is 97/min, respirations are 19/min, and oxygen saturation is 99% on room air. Physical exam is notable for the findings in Figures A and B. The rash seen in Figure B is very coarse. Which of the following is the most likely diagnosis?