Creutzfeldt–Jakob disease (/ˈkrɔɪtsfɛlt ˈjɑːkoʊb/ KROITS-felt YAH-kohb) or CJD is a degenerative neurological disorder that is incurable and invariably fatal. CJD is at times called a human form of mad cow disease (bovine spongiform encephalopathy or BSE). However, given that BSE is believed to be the cause of variant Creutzfeldt–Jakob (vCJD) disease in humans, the two are often confused.CJD is caused by an agent called a prion. Prions are misfolded proteins that replicate by converting their properly folded counterparts, in their host, to the same misfolded structure they possess. CJD causes the brain tissue to degenerate rapidly, and as the disease destroys the brain, the brain develops holes and the texture changes to resemble that of a kitchen sponge.