An Enigmatic Case of a Febrile Infant With Seizures

Area of Science:

• Pediatric Neurology
• Infectious Diseases
• Medical Diagnostics

Background:

• Herpes simplex virus (HSV) encephalitis is a severe infant infection with significant neurological risks.
• Early empiric acyclovir treatment is crucial for symptomatic infants to prevent long-term complications.
• Polymerase chain reaction (PCR) for HSV DNA in cerebrospinal fluid (CSF) is the diagnostic gold standard.

Observation:

• An 8-month-old infant presented with fever and seizures, initially testing negative for HSV DNA via PCR in CSF.
• Persistent symptoms and MRI findings suggestive of meningoencephalitis prompted repeat CSF analysis.
• The repeat CSF sample yielded a positive HSV DNA PCR result.

Findings:

• Initial low viral load can lead to false-negative HSV DNA PCR results in early stages of encephalitis.
• Serial diagnostic testing and clinical assessment are vital for accurate diagnosis.
• A negative initial PCR does not exclude HSV encephalitis, especially with high clinical suspicion.

Implications:

• Clinicians must maintain a high index of suspicion for HSV encephalitis in infants with suggestive symptoms, even with initial negative PCR results.
• Empiric acyclovir therapy should be continued judiciously based on clinical judgment.
• This case highlights the limitations of single diagnostic tests and the importance of repeat testing in pediatric neurology.