The Psychiatric Phenotype of Anti-NMDA Receptor Encephalitis.

In its early stages, anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is often characterized by prominent psychiatric manifestations that can lead to delays in diagnosis and treatment. The authors aimed to address this problem by providing a detailed description of the psychiatric phenotype and demographic features that may influence presentation. Eighty-six patients with positive serum NMDAR antibodies were identified, 22 of whom met diagnostic criteria for anti-NMDAR encephalitis. Medical notes were reviewed retrospectively to rate psychiatric symptoms using standardized scales. Clinical and demographic characteristics were compared for patients with and without psychosis. Patients with psychosis exhibited severe psychopathology with a characteristic phenotype: severe and disproportionate cognitive disturbance (p<0.005) with high negative symptom scores and excitability. Those presenting with psychotic symptoms were significantly younger than those without (p<0.005). Patients with anti-NMDAR encephalitis present with a somewhat distinct cluster of psychiatric symptoms not commonly seen in functional psychoses. When encountered, this atypical pattern should warrant further investigation and a high index of suspicion for anti-NMDAR encephalitis. The more prominent psychotic features in younger adults may reflect greater susceptibility of the young brain to exogenous psychosis.