No neuronal autoantibodies detected in plasma of patients with a bipolar I disorder.

A subpopulation of patients with bipolar disorder type I (BD-I) might suffer from undiagnosed autoimmune encephalitis. We tested plasma of 104 BD-I patients with a current or recent manic episode in the past 2 years for the presence of neuronal autoantibodies using immunohistochemistry, immunocytochemistry and cell-based assay (CBA). Neuronal antibodies were not detected in any of the BD type I. This finding suggests that the frequency of an undiagnosed autoimmune encephalitis in patients with BD I is less than 1%. However, these findings need to be confirmed in cerebrospinal fluid and/or blood of acutely ill manic patients.