PRNP and cerebral amyloid angiopathy: Although prion protein (PrP) is expressed mainly as a glycophosphatidylinositol (GPI)-anchored membrane protein, anchorless PrP is found in certain humans with familial prion disease and can be associated with pathology involving perivascular deposition of amyloid PrPres resulting in cerebral amyloid angiopathy (CAA)[22-26].