Case 3: Unexpected Diagnosis in a Febrile Infant

Presentation

A 34-day-old white boy presents to the emergency department with a fever (101.8°F [38.8°C]) and a 1-day history of poor feeding and fussiness. There is no other history of acute illness, although his older brother currently has oral ulcers secondary to a viral illness. He was born at term after an uncomplicated pregnancy. Maternal prenatal infection screening, including group B Streptococcus, was negative. He was discharged on the second day after birth and had been breastfeeding with good weight gain until the day before admission. Vascular access is obtained, a sepsis evaluation is initiated, and he is treated empirically with ampicillin, cefepime, and acyclovir.

He is admitted to the PICU due to concern for sepsis, where on examination he is awake, alert, and crying. The anterior fontanelle is soft and flat, the tympanic membranes are normal, and the oral mucosa appears pink and moist without lesions. Neurologic examination demonstrates normal tone and strength, and there are no focal deficits. The remainder of the physical examination findings are normal.

Laboratory studies are significant for a white blood cell count of 2,800/μL (2.8×10⁹/L), with an absolute neutrophil count of 180/μL (0.18×10⁹/L). Results of cerebrospinal fluid (CSF) studies show a total protein level of 0.118 g/dL (1.18 g/L), glucose level of 56 mg/dL (3.1 mmol/L), white blood cell count of 13/μL (0.013×10⁹/L), and red blood cell count of 0.052×10⁶/μL (0.052×10¹²/L). The Gram-stain showed no organisms. Herpes simplex and enterovirus polymerase chain reaction (PCR) results are negative. The remainder of the laboratory …