PP13.10 – 2890: Chronic and relapsing paediatric anti-NMDAR encephalitis: Two cases and a literature review

Background Clinical presentation of anti-NMDAR encephalitis is usually by a combination of neurologic, psychiatric and autonomic dysfunction. Prompt recognition and early immunotherapy is associated with better outcomes. The relapse rate has been reported to be 12–24%. Pruss et al. described the presence of NMDAR antibodies in the course of 30% of individuals with herpes simplex encephalitis (HSE). In a paediatric sample with HSE, 7 out of 20 children (35%) relapsed and 3 out of those 7 patients were found to be NMDAR antibodies positive. Case 1 This 12-year-old boy presented with fever and confusion. Herpes simplex DNA PCR was positive on cerebrospinal fluid (CSF). He received intravenous acyclovir with excellent response and clearance of his CSF. He represented few days later with epilepsia partialis continua requiring intensive care unit (ICU) admission. Serum anti-NMDAR antibodies were positive. He was treated with steroids, plasmapharesis, rituximab and cyclophosmide. He made a slow recovery over a few weeks; however serum anti-NMDAR antibodies continue to be positive with persistent elevation of CSF protein over the following 8 months despite regular immunotherapy. Case 2 This 15-year-old girl presented initially with seizures and agitation. She subsequently developed orofacial dyskinesia with worsening encephalopathy and seizures necessitating ICU admission. Serum anti-NMDAR antibodies were positive. She was treated with steroids, plasmapharesis and rituximab with good recovery. She represented 30 months later with psychiatric symptoms. Anti-NMDAR antibodies were positive in the CSF but negative in the serum. She responded well to immunotherapy. Discussion and conclusion: In their large cohort, Titulaer et al defined a relapse as “new onset or worsening of symptoms occurring after at least 2 months of clinical improvement”. Clinical recovery can take up to 18 months, however no literature exists regarding length of seropositivity. These two cases illustrate the variable natural history of the condition.