Creutzfeldt-Jakob disease associated with high titer of antithyroid autoantibodies: case report and literature review.

Hashimoto's encephalopathy and Creutzfeldt-Jakob disease (CJD) often have similar clinical features and may be confused, especially at onset. A 61-year-old woman developed rapidly progressive ataxia, myoclonus and dementia, with abnormalities seen on electroencephalography (EEG). Serum analysis disclosed high titers of antithyroid autoantibodies. Both clinical course and autopsy led to a definitive diagnosis of CJD. This case and a literature review of previous cases confirm that CJD may be confused with Hashimoto's encephalopathy. EEG, clinical and laboratory findings (including the positivity of 14.3.3 protein in the cerebrospinal fluid) are not conclusive for a differential diagnosis, especially at early stages. Only the results of genetic exams can allow a definitive diagnosis in a small percentage of cases while patients are still alive. In patients with unclear symptomatology and rapid onset of myoclonus, dementia and ataxia, the presence of antithyroid antibodies should be examined. If their levels are abnormal, corticosteroid therapy remains mandatory.