Creutzfeldt-Jakob disease (CJD) shares common clinical features with Hashimoto's encephalopathy (HE). The 14-3-3 protein is a relatively sensitive and specific marker of CJD but is not commonly detected in HE. We report the case of a patient with HE with unusual features including positive 14-3-3 protein in the cerebrospinal fluid (CSF) and an atypical course mimicking that of CJD.

A 64-year-old male was admitted due to acute-onset cognitive dysfunction. HE was suspected based on increased titers of anti-thyroid microsomal antibody and an excellent response to steroid. However, 14-3-3 protein was detected in the CSF and a recurrent attack with progressive cognitive decline, pyramidal symptoms and myoclonus mimicking CJD occurred. Cognitive dysfunction showed progressive worsening and the response to steroid treatment was decreased.

14-3-3 protein could be considered a general marker of neuronal destruction and not specific to CJD. The clinical manifestations of HE are variable and its diagnosis is difficult due to the lack of a specific phenotype and reliable diagnostic criteria. We recommend that patients with clinical features of CJD and antithyroid antibodies should be considered for empirical steroid treatment for HE, despite a positive result for 14-3-3 protein.