The etiology of the other forms is well known, including: mutations in the gene encoding PrP for inherited prion diseases; oral exposure to the agent responsible for classical bovine spongiform encephalopathy (BSE) in variant Creutzfeldt-Jakob disease form (vCJD); use of contaminated instruments or materials from human origin such as growth hormone extracted from cadaver-sourced pituitary glands or dura mater graft in iatrogenic forms (iCJD). The gene discussed is PRNP; the disease is variant Creutzfeldt-Jakob disease.