Rare Case of Anti-LGI1 Limbic Encephalitis with New Onset Epilepsy: A Case Report.

Anti-leucine-rich glioma-inactivated 1 (LGI1) limbic encephalitis (LE) has been classified as an autoimmune LE with a subacute course. Many patients with anti-LGI1 LE have normal or minimal cerebrospinal fluid (CSF) findings. Cerebrospinal fluid 14-3-3 protein or neuron specific enolase is usually seen in Creutzfeldt-Jakob disease (CJD) with high sensitivities, but can also be positive in other paraneoplastic and autoimmune encephalitides, which can make diagnosis challenging. The mainstay of treatment for anti-LGI1 LE generally focuses on steroids, intravenous immunoglobulin (IVIG), plasmapheresis, and/or rituximab. All the aforementioned modalities can be used in the treatment of anti-LGI1 LE and since this condition is highly responsive to treatment with steroids, prompt diagnosis can help stall the progression of this disease. Here, we present a case of anti-LGI1 LE that initially improved with empiric immunotherapy and showed definitive return to baseline with initiation of rituximab.