Review Question - QID 108710

A 19-year-old male with a past medical history of surgical repair of a torn anterior cruciate ligament and seasonal allergies presents to the emergency department with a rash. He reports that he first noticed the rash on his torso when he woke up this morning and that it has spread down his legs over the last few hours. He also endorses fatigue, malaise, and sore throat for 4 days. The patient reports that he was seen yesterday at his college’s student health clinic for similar symptoms and was prescribed amoxicillin. He also reports that his younger sister was recently diagnosed with streptococcal pharyngitis and his mother has psoriatic arthritis. He is a sophomore on the soccer team but he has had to sit out of practice for the last several days. His home medications include cetirizine and fluticasone nasal spray. He has no known drug allergies. His temperature is 100.8°F (38.2°C), blood pressure is 122/76 mmHg, pulse is 97/min, and respirations are 16/min. On physical exam, he has an erythematous oropharynx with posterior cervical lymphadenopathy. His rash can be seen in Figure A. Laboratory testing is performed and reveals the following:

Luekocyte count: 20,200/mm^3
Hemoglobin: 14.7 g/dL
Hematocrit: 47%
Mean corpuscular volume: 85 µm^3
Platelet count: 388,000/mm^3

Which of the following is the most appropriate next step for treating this patient's condition?