PRNP and prion disease: All the prion disease entities that have been described so far for decades are based on PrPc that undergoes conformational changes towards more structured states, which provide to the resulting PrPd different properties that tend to overall increase their resistance to degradation compared to PrPc; even diseases that are described as intermediate or protease-sensitive forms (Nor98 and vPSPr) are associated with PrPd that exhibit a more structured conformation than PrPc.