A 4-year-old previously healthy boy is brought to the emergency department with a 3-week history of fever, red eyes, red lips, red tongue, and a rash on his trunk and extremities. He has been irritable, uncomfortable, and has had a sore throat. He is at the 50th percentile for height and the 75th percentile for weight. On examination, temperature is 38.2ºC (100.8ºF), pulse is 120/min, respirations are 30/min, and blood pressure is 110/70 mm Hg. Physical examination reveals conjunctival injection, strawberry tongue, red pharynx with no exudates, desquamation of the palms and soles, and cervical adenopathy. Laboratory tests show an elevated white blood cell count (15500/ul, normal 10200-12700/uL), as well as elevated serum C-reactive protein (8 mg/dl, normal < 3.3 mg/dl). Which of the following is the most likely diagnosis?