Atypical HSV encephalitis with initial negative polymerase chain reaction for HSV DNA

HSV-DNA in cerebrospinal fluid by polymerase chain reaction is considered as the gold standard in the diagnosis of Herpes Simplex Virus (HSV) encephalitis. Sometimes the test may be negative in the initial stage of the disease. HSV-DNA quantitation by polymerase chain reaction should be repeated in 3-7 days if a patient is thought to have HSV encephalitis, as indicated by electroencephalography / magnetic resonance imaging of brain findings even though the initial HSV-DNA quantitation by polymerase chain reaction is negative. We presented two cases with a tentative diagnosis of HSV encephalitis with atypical course, whose polymerase chain reaction results were negative for HSV-DNA initially.