Antithyroperoxidase Antibodies in Encephalopathy: Diagnostic Marker or Incidental Finding?

Patients with acute encephalopathy who are thoroughly examined for an underlying diagnosis and in whom infectious, metabolic, and malignant causes are excluded can form a true diagnostic dilemma. If antithyroperoxidase antibodies (anti-TPO abs) are present, the diagnosis "steroid responsive encephalopathy, associated with autoimmune thyroiditis" (SREAT), better known as Hashimoto encephalitis, will often be considered. The precise pathophysiology of SREAT, including the possible role of the anti-TPO abs and the possible relationship between the encephalopathy and thyroid function, remains to be elucidated. Here we present three young patients with SREAT. Our patients illustrate that in unexplained encephalopathy, after exclusion of other causes (diagnosis of exclusion), determination of the anti-TPO abs may contribute to the diagnosis of SREAT. They also illustrate that thyroid function or the concentration of the anti-TPO abs does not seem to be associated with the severity of the clinical presentation of SREAT. We hypothesize that SREAT has an immunologic etiology. The presence of anti-TPO abs, however, should be considered to be a marker for autoimmunity and not a causative. It probably reflects the presence of predisposition of autoimmunity in these patients. Therefore, this condition should not be called Hashimoto encephalitis any longer.