Autoimmune Psychosis Exists: Early Diagnosis of an Anti-NMDA Receptor Autoimmune Encephalitis Presenting as First-Episode Psychosis in a 25-Year-Old Male-A Case Report.

BACKGROUND: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disorder marked by prominent neuropsychiatric symptoms. It is typically first encountered by psychiatrists because psychotic symptoms can be early signs of the condition. In recent years, this form of encephalitis has been established as a distinct diagnostic entity in neurology and psychiatry. Furthermore, as an organic and autoimmune psychosis, it is considered a differential diagnosis of schizophrenia and schizoaffective disorders.

CLINICAL PRESENTATION: We report the case of a 25-year-old male who presented with a first episode of psychosis. During his stay, the patient exhibited severe cognitive deficits (disorientation, confusion, memory issues), movement disorders (dysarthria, perioral dyskinesia leading to speech difficulties), a decreased level of consciousness, and a catatonic state complicated by a malignant neuroleptic syndrome. The patient also experienced epileptic seizures and had unstable vital signs. An electroencephalogram (EEG) revealed an extreme delta brush pattern (specific for anti-NMDAR encephalitis), and CSF analysis showed an elevated immunoglobulin G (IgG) index. Based on these findings, anti-NMDAR autoimmune encephalitis was suspected 17 days after admission but not yet confirmed. The patient was treated with oral corticosteroids followed by plasmapheresis and showed significant improvement. At discharge, he was alert, oriented, cooperative, and not psychotic, with only mild cognitive defects. Days after discharge, anti-NMDAR IgG antibodies were detected in his CSF, confirming the diagnosis.

CLINICAL PRESENTATION: This case underscores the importance of considering anti-NMDAR autoimmune encephalitis as a differential diagnosis in patients with no personal or family psychiatric history who develop subacute psychotic symptoms (lasting less than 3 months) along with fluctuating neuropsychiatric signs. Conducting an EEG, cerebral MRI, and CSF analysis to confirm or exclude the condition, followed by early immunosuppressive treatment, is crucial for improving prognosis.