Recurrent anti-NMDA receptor encephalitis in first-trimester pregnancy with initially antibody-negative CSF.

Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is a paraneoplastic autoimmune encephalomyelitis that predominantly affects females in their reproductive years Dalmau et al., 2007 and Dalmau et al., 2019. It has been infrequently reported during pregnancy Dono et al., 2023 and Joubert et al., 2020. We describe a case of a 25-year-old G4P2 patient at 11 weeks gestation with a history of anti-NMDAR encephalitis who presented with intermittent confusion for two weeks. Initial antibody tests for anti-NMDAR encephalitis in the cerebrospinal fluid (CSF) were negative. Repeat serum labs drawn upon readmission to the emergency department (ED) 3 weeks later were positive, and results were confirmed with repeat CSF testing. Following treatment, the patient returned to baseline and delivered a developmentally healthy, full-term baby. Current gold-standard testing for anti-NMDAR encephalitis is through detection of NMDAR antibodies in the CSF Gresa-Arribas et al., 2014. However, CSF antibody testing early in the disease course may not be as sensitive as traditionally thought, and repeat testing is indicated if high suspicion continues.