We conducted a retrospective study of consecutive patients meeting clinical criteria for AE evaluated at UC San Diego and Rady Children’s Hospital from January 2007 to November 2021. Survival analysis and cox multivariable regression models were employed to evaluate relapse risk using rituximab exposure as a time-dependent variable.

A total of 35 pediatric (29 seropositive, 6 seronegative) and 75 adult (57 seropositive, 18 seronegative) patients were included in the study. The most common antibody subtype in both cohorts was anti-NMDA receptor (NMDAR). Relapses occurred in 31% of pediatric seropositive, 50% of pediatric seronegative, 38% of adult seropositive, and 27% of adult seronegative cases. Times to first relapse (TTFR) were 10.3 ± 7.4 months (pediatric seropositive), 6.9 ± 4.3 months (pediatric seronegative), 15.4 ± 29.3 months (adult seropositive), and 7.8 ± 6.5 months (adult seronegative). Combining pediatric and adult data, and adjusting for age and sex, rituximab use was associated with 74% lower hazard to relapse (HR 0.26, 95% CI 0.09 – 0.75, p= 0.01) for TTFR and the adjusted HR for rituximab use for recurring relapses was 0.36 (95% CI 0.15 – 0.87, p=0.03). The effect of rituximab was stronger for non-NMDA encephalitis than anti-NMDAR encephalitis (HR 0.39, 95% CI 0.16 – 0.96 vs HR 0.49, 95% CI 0.11 – 2.30).