Hashimoto Encephalopathy of a Middle-Aged Man With Progressive Symptoms of Dementia.

Autoimmune encephalitis is caused by immunological reactions showing unconsciousness, agitation, and other neurological symptoms. Autoimmune diseases can be related to autoantibodies, causing encephalitis. These autoantibody-related encephalitides could appear in various clinical courses. As laboratory tests for detecting these antibodies are limited, diagnosis is difficult. Hashimoto's encephalopathy is autoimmune encephalitis caused by antibodies against the thyroid gland. This time, we experienced a case of a 69-year-old man with a chief complaint of subacute progression of amnesia and suspected autoimmune encephalitis, who was finally diagnosed with Hashimoto's encephalopathy in a rural community hospital. In this case, clinicians should consider Hashimoto's encephalopathy as a differential diagnosis and measure antithyroid antibodies when acute or subacute onset cognitive impairment is observed in middle-aged patients. As a super-aging society significantly affects community hospitals, general physicians need to start treatments for encephalopathy and encephalitis when clinicians suspect the disease and rule out other critical diseases.