There are three types of classic CJD: Sporadic, familial, and Iatrogenic or acquired (which includes Variant CJD). Sporadic is the most common form and accounts for the majority of cases (Mayo Clinic, 2012). The Gale Encyclopedia of medicine (2011) stated, “Most evidence indicates that CJD is caused by abnormally shaped brain proteins called prions that alter the shape of normal PrP proteins, causing them to clump, in a process similar to crystallization, and leading to degeneration of tissue. The source of initial prions in sporadic CJD is unknown, but may result from a spontaneous mutation or change in the PrP gene, the spontaneous conversion of normal PrP into infectious prions.” Sporadic CJD (sCJD) typically affects individuals in later life, between 50-75 years of age. There are about 200-250 cases annually in the United States in which sCJD accounts for at least 85% of cases with an average onset age of 65 years (The Gale Encyclopedia of Medicine, 2011).
Familial CJD (fCJD) is inherited, caused by mutation in the gene that encodes PrP, resulting in the production of abnormally shaped infectious prions (The Gale Encyclopedia of medicine, 2011). According to the Mayo Clinic website (2012), “In the United States, about 5 to 10 percent of people with CJD have a family history of the disease and test positive for a genetic mutation.” Familial CJD also develops within the later years of life.
Iatrogenic or acquired CJD, which accounts for a very small fraction of classic CJD, is caused by exposure to prions during a medical procedure involving human nervous tissue (The Gale Encyclopedia of medicine, 2011). Variant CJD on the other hand, results from eating beef that is infected with BSE (bovine spongiform encephalopathy). BSE is better known as “mad cow disease.” According to the Gale Encyclopedia of medicine (2011), “The majority of identified vCJD cases have occurred in the United Kingdom, as a result of consuming BSE-infected beef. Cases peeked in 1999...
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