A Case of Ovarian Teratoma-Associated Anti-NMDA Receptor Encephalitis in the Presence of Group A Streptococcus Infection.

Background and Aims: Anti-NMDAR encephalitis is a severe autoimmune encephalitis that is frequently associated with ovarian teratomas, whereas infectious triggers remain incompletely understood. We report a case of ovarian teratoma-associated anti-NMDAR encephalitis in a young woman with concurrent Group A Streptococcus infection presenting with prominent psychiatric symptoms and subsequent neurologic decline. Methods: We describe the clinical course, diagnostic evaluation, and multidisciplinary management of a 25-year-old African American woman with acute-onset neuropsychiatric symptoms, confirmed anti-NMDAR encephalitis, bilateral ovarian teratomas, and concurrent Group A Streptococcus infection. Verbal informed consent was obtained from the patient for publication of this case report and any accompanying images. Results: The patient initially presented with acute psychiatric symptoms and was treated for suspected schizoaffective disorder. Further evaluation following clinical deterioration revealed anti-NMDAR antibodies in the cerebrospinal fluid and bilateral ovarian teratomas on imaging. She was treated with IVIG, high-dose corticosteroids, bilateral ovarian cystectomy, and plasma exchange, with subsequent clinical improvement and discharge after prolonged hospitalization. Conclusion: This case underscores the importance of considering anti-NMDAR encephalitis in young women presenting with acute psychiatric symptoms and neurologic decline. It also highlights the importance of pelvic imaging for ovarian teratoma and careful infectious evaluation, including for streptococcal infection when clinically indicated. The observed association between Group A Streptococcus infection preceding symptom onset suggests a possible infectious trigger leading to an immunologic response and subsequent anti-NMDAR encephalitis; however, there is limited evidence of a causal relationship in the literature.