A 4-year-old boy presented to the pediatrician with nontender, mobile lymph nodes on the right side of his neck. He received a 10-day course of amoxicillin clavulanate (Augmentin) for a presumptive diagnosis of acute lymphadenitis with no improvement. There was no associated fever, weight loss, or fatigue. His past medical history was significant for three episodes of pneumonia. There was no history of recent travel or exposure to infectious agents or contacts.