Anti-N-methyl-D-aspartate (NMDA) receptor antibody syndrome is an immune-mediated inflammatory condition of the brain. This syndrome results from antibody formation against NMDA receptors in the brain and may be autoimmune or paraneoplastic in etiology.

Patients will often have a prodromal phase with fevers, headaches, and flu-like symptoms prior to developing neurologic and psychiatric manifestations. Within days to weeks, patients will classically develop prominent psychiatric symptoms (anxiety, hallucinations, delusions, unusual behavior), memory issues, seizures, encephalopathy, abnormal movements (chorea, dystonia, abnormal postures), language impairment, and autonomic instability.

This condition affects both children and adults and has been reported in patients as young as 8 years. Half of female patients over the age of 18 with anti-NMDA receptor antibody syndrome will have an ovarian teratoma. There is also an association of this condition with a prior history of herpes simplex viral encephalitis.