Autoimmune Encephalitis With Positive Anti-Leucine-Rich Glioma-Inactivated 1 (Anti-LGI1) Antibody Mimicking Psychogenic Non-epileptic Seizures.

Autoimmune encephalitis (AIE) represents a significant cause of neurological and psychiatric disorders, often initially misdiagnosed due to a diverse clinical presentation. This case describes a middle-aged woman initially diagnosed with psychogenic non-epileptic seizures (PNES) following emotional stress and depressive symptoms after a family bereavement. Progressive involuntary jerky movements, cognitive dysfunction, and a generalized tonic-clonic seizure raised suspicion for AIE. Diagnostic imaging showed medial temporal lobe hyperintensities, and serological testing confirmed high titers of anti-leucine-rich glioma-inactivated 1 (LGI1) antibodies. The patient showed significant improvement after receiving pulse steroid therapy and intravenous immunoglobulin (IVIG). This case highlights the importance of recognizing psychiatric and neurological overlap in anti-LGI1 encephalitis, emphasizing the need for prompt diagnostic evaluation and early immunomodulatory treatment to optimize patient outcomes.