Diagnostic and Therapeutic Challenges in Herpes Simplex Virus-Triggered Anti-N-Methyl-D-Aspartate Receptor Encephalitis Presenting as Acute Psychiatric Illness in a Young Woman: A Case Report.

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a severe form of autoimmune encephalitis. Symptoms include psychiatric manifestations, seizures, dyskinesias, autonomic instability, and altered consciousness. Recently, Herpes simplex virus (HSV) encephalitis has been recognised as a major cause of secondary autoimmune encephalitis. We report the case of a 23-year-old woman who developed behavioural changes and altered sensorium. She was initially suspected of having a primary psychiatric disorder. Subsequent tests showed the presence of anti-NMDAR antibodies in the cerebrospinal fluid (CSF), and positivity for HSV-1 was confirmed by real-time polymerase chain reaction (PCR). Despite receiving high-dose corticosteroids, IVIG, plasmapheresis, rituximab, acyclovir, and antiviral therapy, the patient was admitted to the ICU, where she stayed for a prolonged period due to respiratory failure, septic shock, and acute kidney injury. This case highlights the diagnostic challenge between viral and autoimmune encephalitis and underlines that patients with acute neuropsychiatric symptoms require early recognition, repeated CSF testing, and multidisciplinary management.