M232R Familial Creutzfeldt-Jacob Disease Challenging to Diagnose Due to the Absence of Characteristic Laboratory Findings.

A 46-year-old man presented with an 8-month history of rapidly progressive dementia (RPD). Diffusion-weighted brain imaging, electroencephalography, and amyloid positron emission tomography revealed no significant findings. Creutzfeldt-Jakob disease (CJD) was considered in the differential diagnosis of RPD, and further testing revealed elevated 14-3-3 protein levels in the cerebrospinal fluid and the M232R mutation in the prion protein gene, confirming a diagnosis of hereditary CJD. We herein report a case of RPD that was challenging to diagnose as hereditary CJD because of the absence of characteristic findings suggestive of CJD on imaging and other examinations.