Creutzfeldt-Jakob disease (CJD) is a rare, worsening, fatal brain disorder. CJD is caused by a type of protein called a prion. Prion proteins occur in both a normal form, which is a harmless protein found in the body's cells, and in an infectious form, which causes disease. Prion diseases can be found in human and in animals.
This disease is rapidly progressive and always fatal. Human infection with this disease leads to death usually within 1 year of onset of illness. CJD occurs worldwide and the estimated annual incidence in many countries, including the United States, has been reported to be about one case per million population.