Review Question - QID 214814

A 5-year-old boy from Nicaragua presents to the emergency room with a 7-day history of fever, sore throat, and rash. The fever and sore throat began on day 1 of the illness, followed by a rash and mouth sores starting on day 2 of the illness. The boy recently attended summer camp. He has no significant past medical history and takes no medications other than a multivitamin. His temperature is 100.1°F (37.8°C), blood pressure is 110/60 mmHg, pulse is 83/min, and respirations are 19/min. On exam, the boy appears fatigued, has multiple erythematous, painful ulcers on the hard palate, buccal mucosa, gingivae, and tongue, and has a rash located on the palms, soles, and buttocks shown in Figure A. Which of the following is the most likely diagnosis?