Anti-leucine-rich glioma inactivated-1 (anti-LGI1) encephalitis is a subgroup of autoimmune encephalitis. We herein report the case of a 60-year-old man who presented with typical symptoms, including short-term memory loss, mental abnormalities, hyponatremia and seizures characterized by faciobrachial dystonic seizures and who was diagnosed with anti-LGI1 encephalitis. At the same time, he was diagnosed with essential thrombocythemia. A significant improvement was obtained by treatment with corticosteroid, immunoglobulin, mycophenolate mofetil, and hydroxyurea. Autoimmune diseases are associated with a significantly increased risk of developing myeloproliferative neoplasms, which may explain the coexistence of anti-LGI1 encephalitis and essential thrombocythema in this patient; however, but more cases and studies are needed to determine whether there is any correlation between these conditions.
Keywords: anti-leucine-rich glioma inactivated-1 encephalitis; essential thrombocythemia; faciobrachial dystonic seizures; myeloproliferative neoplasms; paraneoplastic syndrome.