A kind of autoimmune encephalitis with positive autoantibodies toward the B1 subunit of the gamma-aminobutyric acid-type B receptor is known as anti-GABABR encephalitis. It is an autoimmune brain disorder with typical manifestations of a limbic encephalitis. It can coexist with positive anti-thyroid autoantibodies. We described a 57-year-old woman who was diagnosed with a bipolar affective disorder. The patient had high titers of anti-thyroid peroxidase antibodies, and she also was positive for anti-GABABR antibodies. There is a question, if this case is a kind of comorbidity of anti-thyroid and anti-brain autoimmunity or is it a single nosological entity - a kind of Hashimoto's encephalopathy? (C) 2021 The Author(s) Published by S. Karger AG, Basel