GP45\u2005Autoimmune encephalitis triggered by herpes simplex virus 1 infection

Abstract

Introduction Herpetic encephalitis is the most frequent central nervous system infection in children caused by viral etiology. It may be a trigger for anti-NMDA receptor (NMDAR) encephalitis with the onset of symptoms usually a few weeks after initial presentation with viral encephalitis. Case report Approximately one third of the patients with herpetic encephalitis develop anti-NMDAR encephalitis. There are more hypotheses on how anti-NMDAR encephalitis may develop. First, herpes simplex virus 1 (HSV-1) infection causes an inflammatory destruction of neural tissue with subsequent release of neuronal antigens and formation of NMDAR antibodies; or, second, by molecular mimicry. Onset of symptoms is usually after 2–6 weeks after initial infection with HSV 1. In children symptoms are usually represented by choreoathetosis and orofacial dyskinesias. The diagnosis is made by detecting NMDAR antibodies in cerebrospinal fluid (CSF). We present the case of an 11 months male infant with no previous medical history, who presented with fever, anorexia, seizures with a focal onset and secondarily generalized, somnolence and progressive neurologic deterioration with onset of symptoms 6 days prior to admission. CSF studies showed a hypertensive, hemorrhagic fluid with low levels of glucose. HSV-1 was detected by real time PCR in CSF. Brain MRI revealed multiple cerebral lesions of different sizes predominantly affecting the right hemisphere, thalamus and basal ganglia with diffuse edema. EEG suggested diffuse cerebral dysfunction. Treatment with Acyclovir was started and continued for 28 days with notable decrease in symptom severity. Fever reappeared approximately at 2 weeks after admission. He presented neurologic deterioration with focal seizures, choreiform movements, facial dyskinesia, psychomotor regression to the age of 2 months. These symptoms were suggestive of an autoimmune encephalitis. NMDAR antibodies were detected in CSF. Recurrent HSV encephalitis was excluded. Steroids and Intravenous Immunoglobulins were associated to the therapy scheme. The patient recovered slowly and partially but remained with neurological sequelae. Discussion Our case exemplifies an anti NMDAR encephalitis which developed in the convalescence phase of a viral infection. HSV-1 infection may be a trigger for anti-NMDAR encephalitis. Autoimmune encephalitis after viral infection is important to be recognized early as patients can receive treatment with steroids and immunosuppressants in order to improve their outcome.