|Creutzfeldt-Jakob disease (CJD) is the most common human form of a group of rare, fatal brain disorders known as prion diseases.|
Prion diseases, such as Creutzfeldt-Jakob disease, occur when prion protein, which is found throughout the body but whose normal function isn't yet known, begins folding into an abnormal three-dimensional shape. This shape change gradually triggers prion protein in the brain to fold into the same abnormal shape.
Experts generally recognize the following main types of CJD:
Sporadic CJD develops spontaneously for no known reason. It accounts for 85 percent of cases. On average, sporadic CJD first appears between ages 60 and 65.
Familial CJD is a heredity form caused by certain changes in the prion protein gene. These genetic changes are "dominant," meaning that anyone who inherits a CJD gene from an affected parent will also develop the disorder. Familial CJD accounts for about 10 to 15 percent of cases.
Acquired CJD results from exposure to an external source of abnormal prion protein. These sources estimated to account for about 1 percent of CJD cases. The two most common outside sources are:
Specific Creutzfeldt-Jakob disease symptoms experienced by an individual and the order in which they appear can differ significantly. Some common symptoms include:
Rapid symptom progression is one of the most important clues that a person may have Creutzfeldt-Jakob disease.
There is no single test — or any combination of tests — that can conclusively diagnose sporadic CJD in a living person, but the following tests may help determine whether an individual has CJD:
Sporadic Creutzfeldt-Jakob disease has no known cause. Most scientists believe the disease begins when prion protein somewhere in the brain spontaneously misfolds, triggering a "domino effect" that misfolds prion protein throughout the brain. Genetic variation in the prion protein gene may affect risk of this spontaneous misfolding.
Mutations in the prion protein gene also may play a yet-to-be-determined role in making people susceptible to acquired CJD from external sources. Scientists don't yet know the why acquired CJD seems to be transmitted through such a limited number of external sources. Researchers have found no evidence that the abnormal protein is commonly transmitted through sexual activity or blood transfusions.
Familial CJD is caused by variations in the prion protein gene that guarantee an individual will develop CJD. Researchers have identified more than 50 prion protein mutations in those with inherited CJD. Genetic testing can determine whether family members at risk have inherited a CJD-causing mutation. Experts strongly recommend professional genetic counseling both before and after genetic testing for hereditary CJD.
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There is no treatment that can slow or stop the underlying brain cell destruction caused by Creutzfeldt-Jakob disease and other prion diseases. Various drugs have been tested but have not shown any benefit. Clinical studies of potential CJD treatments are complicated by the rarity of the disease and its rapid progression.
Current therapies focus on treating symptoms and on supporting individuals and families coping with CJD. Doctors may prescribe painkillers such as opiates to treat pain if it occurs. Muscle stiffness and twitching may be treated with muscle-relaxing medications or antiseizure drugs. In the later stages of the disease, individuals with CJD become completely dependent on others for their daily needs and comfort.
CJD progresses rapidly. Those affected lose their ability to move or speak and require full-time care to meet their daily needs. An estimated 90 percent of those diagnosed with sporadic CJD die within one year. Those affected by familial CJD tend to develop the disorder at an earlier age and survive somewhat longer than those with the sporadic form, as do those diagnosed with vCJD. Scientists have not yet learned the reason for these differences in survival.