[A case of herpes simplex virus encephalitis recurring after a seven-year interval]

In January 2008, a 59-year-old man with a history of diabetes mellitus was admitted to our hospital with herpes simplex virus (HSV) encephalitis of his right temporal lobe, which was diagnosed by PCR testing of his cerebrospinal fluid (CSF). He was treated with intravenous acyclovir for three weeks and made a full recovery. On discharge, his CSF was negative for HSV on PCR testing. Seven years later, in March 2015, the man was readmitted to our hospital with fever, disorientation, and nominal dysphasia. Diffusion-weighted MRI of his head revealed a high-intensity area in his left temporal lobe. Testing of his CSF revealed a moderately increased monocyte count and HSV on PCR testing, so he was diagnosed with recurrent HSV encephalitis. He was treated with intravenous acyclovir for three weeks. On discharge, his CSF was negative for HSV on PCR testing, but he had mild residual amnesia. There have been few reports of HSV encephalitis with viral reactivation recurring after a long remission period in adults. This case illustrates the need for prolonged follow up of individuals with HSV encephalitis in order to detect recurrences.