[A case of Hashimoto's encephalopathy successfully treated with oral steroid therapy, resistant to high-dose methylprednisolone, plasma exchange and intravenous immunoglobulin].

A 30-year-old woman was admitted to the first institution with subacutely progressive aphasia and depression. Despite of lacking conclusive evidence on magnetic resonance imaging, cerebrospinal fluid examination, or electroencephalogram, we tentatively diagnosed her disease as limbic encephalopathy due to its acute progression. High-dose methylprednisolone was started on admission. However, symptoms did not improve. To make matters worse, psychiatric symptoms, such as hallucinations and emotional incontinence, appeared on the same day. Additional treatment with plasma exchange and intravenous immunoglobulin administration was also ineffective. Therefore, we could not manage the patient in a general ward due to severe psychiatric symptoms. The patient was transferred to a psychiatric ward in the second institution. She received both psychiatric treatment and steroid therapy, including a second course of intravenous high-dose methylprednisolone, followed by long-term oral prednisolone. Her symptoms gradually improved. A final diagnosis of Hashimoto's encephalopathy was made based on the patient's clinical course and positive results for both serum anti-thyroid antibody and anti-NAE antibody. In our case, long-term oral steroid therapy under psychiatric treatment was effective for good outcome.