An 11-year-old boy with a medical history of allergic rhinitis presented to the emergency department of a children’s hospital with 2 weeks of painful left-sided neck swelling and fever. He had accompanying night sweats, fatigue, and decreased appetite. Initial physical examination revealed multiple distinct matted, firm left-sided cervical lymph nodes.
Laboratory evaluation was notable for leukopenia with a white blood cell count of 3700/µL (to convert to 109/L, multiply by 0.001), a microcytic anemia with a hemoglobin of 10.7 g/dL (to convert to g/L, multiply by 10), mean corpuscular volume of 58 µm3 (to convert to fL, multiply by 1), an elevated lactate dehydrogenase level of 548 U/L (to convert to µkat/L, multiply by 0.0167), and an elevated erythrocyte sedimentation rate of 35 mm/h. Purified protein derivative and infectious mononucleosis testing were negative.