Background: NMDA receptor encephalitis is a rare autoimmune disorder characterized by the production of antibodies against the N-methyl-D-aspartate (NMDA) receptors in the brain. It often presents with a variety of neurological and psychiatric symptoms, including seizures, speech impairment, and behavioral changes.

Patient: We present the case of a 4-year-old girl initially diagnosed with focal epilepsy of unknown etiology, who exhibited speech regression and behavioral changes. Despite treatment with antiepileptic medication, her symptoms persisted and worsened over time.

Results: Further evaluation, including imaging studies and EEG monitoring, did not reveal any significant abnormalities. However, autoimmune encephalitis was suspected due to the atypical presentation and lack of response to conventional treatments. Serum testing confirmed the presence of NMDA receptor antibodies. The patient was subsequently treated with high-dose steroids for 5 days, which led to a remarkable improvement in her condition. Within a week of discharge, she began speaking in full sentences again.

Conclusion: This case highlights the importance of considering autoimmune encephalitis in children presenting with atypical seizure manifestations and behavioral changes. Prompt recognition and treatment with immunomodulatory therapy, such as high-dose steroids, can result in significant clinical improvement and better outcomes for these patients.