A nine-week-old girl with fever and seizures

CASE PRESENTATION A nine-week-old girl presented to the emergency department with a 12 h history of fever and a 1 min generalized tonic-clonic seizure. Review of systems was otherwise negative. Her two-year-old sister experienced a fever and oropharyngeal ulcers two weeks before. On physical examination, she was febrile to 39.2°C rectal, but with otherwise normal vital signs. She was well-appearing and her examination was normal, including the neurological examination. Blood, urine and cerebrospinal fluid (CSF) specimens were obtained, and intravenous ceftriaxone, vancomycin and acyclovir were started. Laboratory investigations showed a normal complete blood cell count and transaminase levels. CSF examination revealed 55 white blood cells/μL (51% monocytes, 37% lymphocytes, 12% neutrophils), 7 red blood cells/μL, normal protein (0.35 g/L) and normal glucose (2.9 mmol/L). An electroencephalogram revealed active epileptiform activity over the right centroparietal regions. She was admitted to the pediatric ward and underwent magnetic resonance imaging of her head, which revealed multifocal nonenhancing lesions in the subcortical white matter of the right precentral gyrus, right cingular gyrus, right corticospinal tract, as well as the right internal capsule and thalamus (Figure 1). Bacterial cultures were without growth and antibiotics were discontinued after 48 h. CSF herpes simplex virus (HSV) 1 and HSV 2 polymerase chain reaction (PCR) (LightCycler 2.0 HSV 1/2 qualitative kit [Roche Diagnostics, Canada]) and enterovirus PCR were also negative. Repeat lumbar puncture and blood testing were performed on hospital day 3. DIAGNOSIS Both the CSF and blood samples obtained on hospital day 3 returned positive results for HSV-1 using PCR, confirming a diagnosis of HSV encephalitis. Extracted DNA from the initial CSF was re-tested using a different laboratory-developed HSV 1 and HSV 2 quantitative realtime PCR assay at another reference laboratory. In retrospect, the initial CSF specimen was positive for HSV 1 (2,675 copies/mL) using this assay, as were the second CSF specimen (21,905 copies/mL) and the blood sample (12,089 copies/mL).