Acyclovir resistant acute herpes simplex encephalitis associated with acute retinal necrosis: A case report and review of the literature.

A 55-year-old man was admitted to our hospital for investigation of high fever, decreased consciousness and bilateral visual impairment. His cerebrospinal fluid analysis revealed pleocytosis of mononuclear cells and an increased protein concentration. FLAIR images revealed multiple high-intensity lesions in the frontal lobe, part of which was enhanced with gadolinium. Despite initiating treatment with acyclovir and corticosteroids, his consciousness and visual acuity deteriorated. Immunopathological examination of brain biopsies showed numerous herpes simplex virus type 2-positive neurons and macrophages, leading to a diagnosis of herpes simplex encephalitis (HSE). Fundoscopic examination revealed multiple foci of retinitis with vasculopathies, and inflammation in the anterior chamber and vitreous, indicating acute retinal necrosis (ARN). Foscarnet treatment was initiated in place of acyclovir and his consciousness improved, with a slight improvement in visual acuity. ARN is typically caused by a herpes virus infection limited to the eyeball, and rarely in combination with HSE. In such cases, there is a latency of approximately 2-4 weeks between ARN and the onset of encephalitis. Our case is unique in that HSE and ARN developed simultaneously, and it highlights that there may not always be a latency between the onsets of the two disorders. Finally, foscarnet should be considered in cases of HSE and ARN with acyclovir resistance.