Anti-NMDA Receptor Encephalitis: A Case of Atypical Psychosis with Absence of Neurological Symptom

Introduction: Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis is an autoimmune disorder in which antibodies attack NMDA receptors at central neuronal synapses. Symptoms include a highly characteristic set of neurological symptoms but also prominent psychiatric manifestations. Misdiagnosis is frequent given the overlap of symptoms with psychiatric manifestations. Case Report:  This is a case of a healthy 26 year old man with history of polysubstance abuse whom complained of intermittent dizziness, fatiguability & myalgia. He also experienced elementary in nature auditory hallucinations which were transient and resolve spontaneously. He presented to the Emergency Department weeks later with psychiatric manifestations. CT brain was normal. He was admitted to the psychiatry ward. Throughout his detention he was restrained & isolated due to provocative behaviour. In view of poor response to optimised poly psychotropics MRI brain done showed multiple T2/FLAIR hyperintense foci in both centrum semiovale, right parietal lobe, right frontal lobe & left temporal lobe. He was treated as old infarct secondary to previous illicit drug abuse. Despite being treated with optimal doses and duration of multiple antipsychotics, his psychosis failed to improve. Due to the atypicality of his psychotic episode, he was investigated for anti NMDA receptor encephalitis, which he tested positive for. He was immediately transferred to the medical ward and treated with IVIG. He subsequently showed improvement. However, he was noted to have regressive personality changes. Conclusion: This case underscores the need for increased awareness and high diagnostic suspicion of this rare clinical syndrome when approaching patients with acute onset of atypical psychosis. Prompt diagnosis is critical as early immunotherapy could dramatically affect outcomes.