Retrospective case series.

A 9-year-old boy presented with seizures, right arm numbness and weakness and hallucinations. Workup was notable for MRI brain with biparietal cortical/subcortical edema and positive cerebrospinal fluid (CSF) anti-NMDAR antibodies. He was initially treated with IVIg, steroids and rituximab. Over the course of 3 years, he had waxing and waning aggression, anxiety and psychosis despite initial response to additional immunotherapies, including cyclophosphamide, plasma exchange, tocilizumab, mycophenolate. Finally after the addition of daratumumab he had near complete resolution of his neuropsychiatric symptoms. He is now stable on monthly maintenance daratumumab and replacement IVIg.

A 16-year-old adolescent girl presented with behavior change, hallucinations and seizures prompting workup for AIE, which revealed CSF anti-NMDA receptor antibodies. She started IVIg, steroids plasma exchange and rituximab. However, 5 months after initial presentation she had persistent aggression, hallucinations, and seizures. PLEX was repeated and Daratumumab was administered with significant improvement in her behavioral and psychiatric symptoms, followed by return to school.

In this report, we describe two cases of pediatric anti-NMDAR encephalitis that responded to daratumumab, highlighting a potential therapeutic option to be explored in treatment-refractory cases.