Review Question - QID 211033

A 24-year-old man presents to his primary care provider with a complaint of fever, cough, and fatigue for the past 7 days. The patient reports that his symptoms are interfering with his responsibilities as a graduate student. Review of systems is positive for decreased appetite and myalgia but negative for sore throat, nausea, vomiting, diarrhea, or constipation.  He has been in a relationship with his current girlfriend for the past 2 months. Temperature is 100.8°F (38.2°C), blood pressure is 123/84 mmHg, pulse is 96/min, and respirations are 18/min. Inspection of the throat shows no erythema or petechiae. No cervical lymphadenopathy is appreciated. Laboratory results yield the following:
 
Serum:
Hemoglobin: 14 g/dL
Hematocrit: 47%
Leukocyte count: 18,000/mm^3 with 65% lymphocytes
Platelet count: 342,000/mm^3
Alkaline phosphatase: 65 U/L
Total bilirubin: 0.9 mg/dL
Direct bilirubin: 0.11 mg/dL
AST: 140 U/L
ALT: 132 U/L
Heterophile antibodies: Negative

A peripheral smear of the patient’s blood is obtained and can be seen in Figure A. Which of the following is the most likely diagnosis?