Anti-NMDA receptor encephalitis following Murray Valley encephalitis: a case report

Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis is an autoimmune condition that is increasingly being recognized as a complication of central nervous system infections. While association with herpes simplex virus encephalitis is well established, the condition has also been reported to occur following Japanese encephalitis virus infection and yellow fever vaccination.

Here, we report a case of anti-NMDA receptor encephalitis following infection with Murray Valley encephalitis virus (MVEV), another virus of the family Flaviviridae. Following initial recovery, and 34 days after the onset of illness, our patient developed autonomic instability, orofacial dyskinesia, and decreased level of consciousness. Diagnosis was established with the detection of anti-NMDA receptor antibodies in cerebrospinal fluid. Immunosuppressive therapy with rituximab and corticosteroids resulted in a favorable outcome.

This case report raises awareness of post-viral autoimmune encephalitis which should be considered in patients with a biphasic pattern of illness following viral encephalitis or a compatible clinical syndrome. Given the initial diagnosis of Murray Valley encephalitis, clinicians should be alert to the possibility of MVEV as an infectious trigger associated with the development of anti-NMDA receptor encephalitis. We also highlight the challenges inherent in the diagnosis of flavivirus infections, which may require a combination of clinical, epidemiological, and laboratory evidence.