Recurrence of acyclovir-resistant herpes encephalitis in an immunocompromised patient: A case report

Acyclovir (ACV)-resistant herpes simplex virus (HSV) strains have emerged and gradually increased in number. Prolonged treatment, such as for immunocompromised patients, has been observed on many occasions to lead to the development of resistance. Additionally, some strains of HSV exist that are ACV resistant, and they can cause severe complications that may be impossible to treat with current therapies. We report the first case of ACV-resistant herpes encephalitis (ARHE) recurring in an immunocompromised adult patient without neurosurgical intervention.

A 58-year-old man with a fever of 38°C had tremors. Evaluation revealed 14 points on the Glasgow Coma Scale with 39°C fever but unremarkable physical examination. Diagnosis was infection of unknown origin; fever continued, and the Glasgow Coma Scale worsened to 8. Imaging showing a high-intensity area between the left temporal lobe and insular cortex suggested herpes encephalitis. ACV was started. Cerebrospinal fluid (CSF) was positive for HSV DNA, confirming the diagnosis. However, unresolved symptoms suggested ARHE; therefore, we initiated vidarabine treatment. Later testing confirmed ARHE. Foscarnet was started based on a hospital day 25 blood test revealing pancytopenia, possibly from vidarabine. Consciousness improved, and the patient moved to rehabilitation. However, symptoms worsened, suggesting recurrence. Diffusion-weighted magnetic resonance imaging revealed a high high-intensity area around the right temporal lobe; CSF was positive for HSV DNA, confirming recurrent herpes encephalitis. ACV and foscarnet were initiated. Fever decreased, consciousness improved, and HSV DNA on hospital days 78 and 93 was CSF negative. Treatment was terminated on hospital day 86.

ARHE recurred in the patient following remission; therefore, it is necessary to discuss the length of the treatment period.