Genetic forms are associated with mutations in the PRNP gene and comprise genetic/familial CJD (gCJD), familial fatal insomnia (FFI) and PrP- amyloidoses, which include Gerstmann-Sträussler-Scheinker disease (GSS), PrP-cerebral amyloid angiopathy (PrP-CAA) and PrP systemic amyloidosis (PrP-SA) [2,3]. Here, PRNP is linked to fatal familial insomnia.