Creutzfeldt-Jakob disease (CJD) is the most common human form of a group of rare, fatal brain disorders known as prion diseases.
About Creutzfeldt-Jakob disease
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.
CJD causes a type of dementia that gets worse unusually fast. More common causes of dementia, such as Alzheimer's, dementia with Lewy bodies and frontotemporal dementia, typically progress more slowly.
Through a process scientists don't yet understand, misfolded prion protein destroys brain cells. Resulting damage leads to rapid decline in thinking and reasoning as well as involuntary muscle movements, confusion, difficulty walking and mood changes.
CJD is rare, occurring in about one in 1 million people annually worldwide.
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 caused by certain changes in the chromosome 20 gene coding the biological blueprint for prion protein. People who develop familial CJD do so because they inherited the genetic changes from a parent. Familial CJD accounts for about 10 to 15 percent of cases. It develops, on average, at a younger age than sporadic CJD, with some genetic types appearing as early as ages 20 to 40.
- Acquired CJD results from exposure to an external source of abnormal prion protein. These sources are estimated to account for about 1 percent of CJD cases. The two most common outside sources are:
- Medical procedures involving instruments used in neurosurgery, growth hormone from human sources or certain transplanted human tissues. The risk of CJD from medical procedures has been greatly reduced by improved sterilization techniques, new single-use instruments and synthetic sources of growth hormone.
- Meat or other products from cattle infected with bovine spongiform encephalopathy ("mad cow disease"), recognized in the mid-1990s as the cause of variant CJD (vCJD). Scientists traced this new type of CJD to consumption of beef from cattle whose feed included processed brain tissue from other animals.
Chronic wasting disease
This prion disease is similar to mad cow disease that's been found in wild deer, elk and moose. According to the Centers for Disease Control (CDC), there's no evidence to date that the disease has been transmitted to humans.
Learn More From the CDC
Specific Creutzfeldt-Jakob disease symptoms experienced by an individual and the order in which they appear can differ significantly. Some common symptoms include:
- Agitation, apathy and mood swings.
- Rapidly worsening confusion, disorientation, and problems with memory, thinking, planning and judgment.
- Difficulty walking.
- Muscle stiffness, twitches and involuntary jerky movements.
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:
- Electroencephalogram (EEG) measures the brain's patterns of electrical activity similar to the way an electrocardiogram (ECG) measures the heart's electrical activity.
- Brain magnetic resonance imaging (MRI) can detect certain brain changes consistent with CJD.
- Lumbar puncture (spinal tap) tests spinal fluid for the presence of certain proteins.
Causes and risks
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 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 increases the risk of an individual developing 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.
Treatment and outcomes
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.
- What Is Dementia?