Prions

A newly discovered type of disease-causing agent, neither bacterial nor fungal nor viral, and containing no genetic material. A prion is a protein that occurs normally in a harmless form. By folding into an aberrant shape, the normal prion turns into a rogue agent. It then coopts other normal prions to become rogue prions. Prions have been held responsible for a number of degenerative brain diseases, including mad cow disease, Creutzfeldt- Jacob disease, fatal familial insomnia, kuru, an unusual form of hereditary dementia known as Gertsmann-Straeussler-Scheinker disease, and possibly some cases of Alzheimer's disease. Dr. Stanley B. Prusiner received the 1997 Nobel Prize in physiology or Medicine for his discovery of prions.