Creutzfeldt-Jakob disease (CJD) is a rare, degenerative, fatal brain disorder. It affects about one person in every one million per year worldwide; in the United States there are about 350 cases per year. CJD usually appears in later life and runs a rapid course. Typical onset of symptoms occurs at about age 60, and about 70 percent of individuals die within one year. In the early stages of the disease, people may have failing memory, behavioral changes, lack of coordination, and visual disturbances. As the illness progresses, mental deterioration becomes pronounced and involuntary movements, blindness, weakness of extremities, and coma may occur.
There are three major categories of CJD.
In sporadic CJD, the disease appears even though the person has no known risk factors for the disease. This is by far the most common type of CJD and accounts for at least 85 percent of cases. In hereditary CJD, the person may have a family history of the disease and test positive for a genetic mutation associated with CJD. About 10 to 15 percent of cases of CJD in the United States are hereditary. In acquired CJD, the disease is transmitted by exposure to brain or nervous system tissue, usually through certain medical procedures. There is no evidence that CJD is contagious through casual contact with someone who has CJD. Since CJD was first described in 1920, fewer than one percent of cases have been acquired CJD. A type of CJD called variant CJD (or vCJD) can be acquired by eating meat from cattle affected by a disease similar to CJD called bovine spongiform encephalopathy (BSE) or, commonly, “mad cow” disease. CJD belongs to a family of human and animal diseases known as the transmissible spongiform encephalopathies (TSEs) or prion diseases. A prion—derived from “protein” and “infectious”—causes CJD in people and TSEs in animals. Spongiform refers to the characteristic appearance of infected brains, which become filled with holes until they resemble sponges when examined under a microscope. CJD is the most common of the known human TSEs. Other human TSEs include kuru, fatal familial insomnia (FFI), and Gerstmann-Straussler-Scheinker disease (GSS). Kuru was identified in people of an isolated tribe who practiced ritual cannibalisms in Papua, New Guinea and has now almost disappeared. Kuru is considered an acquired prion disease. FFI and GSS are extremely rare hereditary diseases, found in just a few families around the world. To date, about 260 cases of vCJD, mostly in the United Kingdom, have been reported related to consuming beef but none in which the disease was acquired in the U.S. Other TSEs are found in specific kinds of animals. These include BSE, mink encephalopathy, feline encephalopathy, and scrapie, which affects sheep and goats. Chronic wasting disease (CWD) affects elk and deer and is increasingly prevalent in certain areas in the United States. To date no transmission of CWD to humans has been reported.
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