Risk Factors and Causes of Creutzfeldt-Jakob Disease
Sporadic CJD develops when normal prions spontaneously change into infectious prions and then alter other cells. Infectious prions stick together, forming fibers and plaques that accumulate in brain tissue. These fibers and plaques can be detected years before CJD symptoms develop.
Familial CJD is caused by a genetic abnormality (mutation) that results in infectious prion formation. Several types of prion gene mutations have been identified, and the specific type affects how often the disease occurs within a family and the severity of the symptoms. Other risk factors play a role in the development of the disease because not all people with the genetic abnormality will develop CJD.
People who consume contaminated beef may be at increased risk for developing an acquired form of Creutzfeldt-Jakob disease called variant CJD (vCJD). Although this risk has not been proven, there is a strong similarity between the prions that cause mad cow disease (BSE) and vCJD. In Europe, several cases of the disease have occurred in younger than average patients following an outbreak of BSE.
Rarely, iatrogenic CJD (iCJD) is acquired as a result of a medical procedure or treatment (e.g., organ or tissue transplant, graft, human growth hormone [hGH] therapy) that exposes the central nervous system to prion-contaminated tissue or medical instruments.
CJD is not contagious, but direct or indirect contact with the blood, tissue, or spinal cord fluid of patients with the disease should be avoided to prevent transmission. Patients with suspected or confirmed CJD, and those at increased risk for the disease because of family history, should never donate blood, tissue, or organs.
CJD Signs and Symptoms
Symptoms of CJD are similar to those of other neurological conditions and diagnosis cannot be made on the basis of symptoms alone. Symptoms develop rapidly and may include the following:
- Behavioral changes (e.g., impaired judgment and reasoning)
- Involuntary movements
- Lack of coordination
- Memory loss
- Progressive loss of cognitive function (dementia)
- Unusual physical sensations
- Vision disturbances
As the disease progresses, blindness, extreme muscle weakness, and coma are common. Coma patients often develop pneumonia and other infections. In most cases, CJD is fatal within a year of onset.
Variant CJD is more common in younger patients and progresses more slowly than other types.