Creutzfeldt-Jakob disease (CJD), the most frequent TSE, exists in three forms: sporadic CJD (sCJD), of unknown aetiology; genetic CJD (gCJD), i.e. caused by mutations in PrP-encoding gene, PRNP; and acquired CJD, either variant (vCJD) or accidentally transmitted (atCJD) [1]. The gene discussed is PRNP; the disease is human prion disease.