PRNP and prion disease: Different molecular events favor PrPC-PrPSc misfolding and account for the heterogeneity in prion diseases etiology: the conversion can be produced as a rare spontaneous stochastic event, as a consequence of mutations in PrPC-encoding gene, or induced by exogenous PrPSc that forces PrPC misfolding, acting as a template [23,24,25].