[Herpes simplex encephalitis without cerebrospinal fluid pleocytosis in a patient with bullous pemphigoid: a case report].

A 78-year-old woman was diagnosed with bullous pemphigoid 2 months ago, and she had been treated with steroid and plasmapheresis. She developed sudden fever, vomiting, disorientation, and abnormal behavior. Diffusion weighted images and fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images showed high-intensity signals in the right temporal lobe hippocampus and right insular cortex. Cerebrospinal fluid (CSF) examination showed normal cell count (4/mm(3)), but was positive for HSV1-DNA by PCR. She was diagnosed with herpes simplex encephalitis (HSE), and acyclovir was started on the first day of admission. She had complete recovery, and was discharged. She didn't show CSF pleocytosis throughout her course of HSE. No CSF pleocytosis could be due probably to her immunosuppressed state under the steroid therapy for bullous pemphigoid. Because the morbidity and mortality of HSE is drastically reduced by early antiviral treatment, it is important to accelerate the diagnosis and treatment of HSE, especially in immunosuppressed or immunocompromised hosts.