PRNP and sporadic Creutzfeldt-Jakob disease: Clinical phenotypes of IPD are highly heterogeneous and include rapidly progressive forms of dementia and/or ataxia (indistinguishable from sporadic Creutzfeldt-Jakob disease [CJD]), fatal familial insomnia and more slowly progressive syndromes such as Gerstmann-Straussler-Scheinker disease and PrP systemic amyloidosis (Mead and Reilly, 2015, Mead et al., 2013).