Anti-NMDA receptor encephalitis presenting as an acute psychotic episode misdiagnosed as dissociative disorder: a case report

BACKGROUND: In 2005, “anti-N-methyl-d-aspartate (NMDA) receptor encephalitis,” a syndrome with prominent psychiatric symptoms, memory loss, decrease in level of consciousness, and central hypoventilation, was described in young women with ovarian teratomas and antibodies against an antigen highly expressed in the hippocampus. This report highlights the growing need for increased awareness among psychiatrists and other relevant medical professionals about this under-diagnosed disorder, which should be considered in differential diagnoses. CASE PRESENTATION: A 19-year-old female with no psychiatric history presented to a district general hospital with acute psychosis, emotional lability, memory deficit, fluctuating behavioral changes such as wandering and babbling, and seizure. She was admitted to the hospital with a provisional diagnosis of dissociative disorder. Soon after admission, she developed aspiration pneumonia and was intubated for mechanical ventilation. She was transferred to our hospital for further assessment and admitted to the intensive care unit for ventilation. Laboratory test results were unremarkable, but her EEG showed non-specific slowing with no epileptiform activity, and brain computed tomography (CT) and MRI also showed no remarkable findings. Cerebrospinal fluid (CSF) analysis showed an elevated white blood cell count (15 cells/hpf; 70 % lymphocytes), and blood serum and CSF samples tested positive for NMDA receptor antibodies. Abdominal contrast-enhanced CT revealed an ovarian teratoma, which was subsequently removed laparoscopically. Postoperative immunotherapy (steroids, intravenous immunoglobulin, and plasmapheresis) led to gradual improvement. On day 25 of hospitalization, neuropsychological assessment demonstrated that overall, she had returned to her premorbid level of functioning. Her condition substantially improved over several months of cognitive rehabilitation, and she was eventually discharged on day 75. CONCLUSIONS: Anti-NMDA receptor encephalitis, a form of autoimmune encephalitis, is commonly associated with tumors and often misdiagnosed. Diagnosis can be confirmed by detecting NMDA receptor antibodies in the patient’s serum or CSF. Management can be achieved with immunosuppressive therapy and tumor resection.