Hashimoto's encephalopathy (HE) is a rare neurological disorder with a heterogeneous group of neurological symptoms associated with high titres of anti-thyroid antibodies. Clinical manifestations may include encephalopathic features such as seizures, behavioural and psychiatric manifestations, movement disorders and coma. The objective of this presentation is to describe a patient with this rare and controversial clinical syndrome mimicking Creutzfeldt-Jakob disease, associated with a Hashimoto euthyroid thyroiditis and with a significant response to high dose intravenous prednisone. The responsiveness of this syndrome to steroids suggests that this disorder involves immune pathogenic mechanisms, as previous reviews reported.