Hashimoto's encephalopathy mimicking presenile dementia.

Hashimoto's encephalopathy (HE), which carries kaleidoscopic clinical presentations, is easily misdiagnosed in clinical practice. Early diagnosis and prompt initiation of steroid therapy are associated with good prognosis. We describe a 50-year-old female patient who had subclinical hypothyroidism and who presented herself with gradual cognitive impairment, accompanied with auditory hallucination and delusion. Increased anti-thyroid antibodies titers were found in her serum and cerebrospinal fluid. The HE diagnosis was confirmed using the laboratory test for anti-thyroid antibodies along with the patient's clinical presentation. We treated her with steroid pulse therapy, and the results were favorable. We highlight this case to call for early diagnosis and prompt intervention of HE in clinical practice.