Herpes simplex encephalitis with two false-negative cerebrospinal fluid PCR tests and review of negative PCR results in the clinical setting.

Introduction: Herpes simplex virus encephalitis (HSE) is an acute infection accompanied by significant morbidity and mortality with the diagnosis often made by cerebrospinal fluid (CSF) polymerase chain reaction (PCR) testing.

Case Presentation: We report a case of a healthy 35-year-old woman presenting with altered mental status. Due to suspicion of herpes encephalitis, a CSF PCR for herpes virus was sent for examination and acyclovir was started.