Patient with concurrent anti-NMDAR autoimmune encephalitis and immature teratoma of the ovary

In young women with anti-N-methyl-D-aspartate receptor (anti-NMDAR) autoimmune encephalitis (AE), co-occurrence with ovarian teratoma is common. While the management of mature teratoma with AE is well documented, literature on managing immature teratoma (IT) in tandem with AE is relatively scarce. Here, we report a case of a female patient in her early adolescence who presented with abdominal pain and was diagnosed with grade 3 IT combined with anti-NMDAR AE after an ovarian tumour was discovered and resected. Postsurgery, the patient received immunotherapy, chemotherapy and antiepileptic therapy, and two follow-up evaluations showed no signs of recurrence or sequelae. This case highlights the importance of a high index of suspicion for concurrent AE in the presence of ovarian teratoma, particularly IT, and the crucial role of concurrent administration of immunotherapy and chemotherapy following tumour resection in impacting prognosis.