Although controlled studies have not been done to determine whether this rate of family history of dementia differs from other diagnoses, it is nominally higher than the 12.1% reported in sporadic CJD [24], leading to speculation that VPSPr might be a form of genetic prion disease with a cause other than PRNP coding variants [7,8]. Here, PRNP is linked to sporadic Creutzfeldt-Jakob disease.