PRNP and fatal familial insomnia: Genetic prion diseases such as familial Creutzfeldt-Jakob disease (fCJD), Gerstmann-Sträussler-Sheinker syndrome (GSS), and fatal familial insomnia (FFI) are caused by mutation of PRNP.1–3 Acquired Creutzfeldt-Jakob disease is caused by abnormal prion protein, which is transmitted by cadaveric dura mater grafts (dCJD), cadaveric corneas, growth hormone prepared from human pituitary glands, and beef affected by bovine spongiform encephalopathy (variant Creutzfeldt-Jakob disease or vCJD).1–4 Prion diseases are progressive, untreatable, and fatal brain disorders.