1. Oze Henig, MD*,† 2. Soma Jyonouchi, MD‡,§ 3. Torsten Joerger, MD¶ 4. Katie Kennedy, MD‡ 1. *Division of General Pediatrics 2. ‡Division of Allergy and Immunology, and 3. ¶Department of Infectious Disease, Children’s Hospital of Philadelphia, Philadelphia, PA 4. †Children’s Hospital of Philadelphia Inpatient Pediatrics at Virtua, Voorhees, NJ 5. §Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA A previously healthy 5-year-old girl presents to the pediatric emergency department of a community hospital with 3 days of fever and neck swelling. She reports pain when moving the neck upward and to the right, but there is no neck stiffness. On physical examination she has a temperature of 102.2°F (39°C) but is well appearing. She has a 2-cm, left-sided, mobile, tender mass along the anterior cervical chain and shotty lymphadenopathy of the right anterior cervical chain. She is diagnosed as having lymphadenitis and is discharged with a prescription for clindamycin. Despite consistently taking the antibiotic, she returns 3 days later with persistent fever and worsening swelling. On physical examination her left-sided swelling has increased to 3 cm, but she continues to have normal range of motion of her neck. A complete blood cell count reveals a white blood cell count of 11,000/µL (11×109/L); hemoglobin concentration, 9.0 g/dL (90 g/L); and platelet count, 424×103/µL (424×109/L). The differential cell count includes 63% neutrophils, 24% lymphocytes, 12% monocytes, and 1% eosinophils. Ultrasonography is performed and demonstrates 2 lymph nodes in the left cervical chain that seem reactive in nature and with no abscess formation. The patient is admitted on intravenous (IV) ampicillin-sulbactam for presumed outpatient treatment failure of acute lymphadenitis. However, her symptoms persist, and further testing is needed to reveal the etiology of her infection. While receiving IV ampicillin-sulbactam, the patient continued to have persistent fever. Serologic tests for Epstein-Barr virus, cytomegalovirus, and Bartonella henselae as well as a tuberculin skin test and rapid human immunodeficiency virus testing were negative. A chest radiograph showed no abnormality. After 10 days of fever with stable physical examination findings, otolaryngology performed an excisional biopsy, with resultant …