APOE and prion disease: While in prion diseases epidemiological studies showed no clear effect of APOE polymorphism on the risk of disease occurrence [72, 95, 126], clinical and neuropathological studies evaluating possible effects of APOE polymorphism on the rate of prion disease progression and pathology burden have not been done due to limited number of available cases, disease diversity, and restrictions related to infection precaution concerning work with human prion material [33, 79, 126].