Creutzfeldt-Jakob (KROYTZ-felt YAH-kub) disease is a disorder of the brain that is ultimately fatal.
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Bovine spongiform encephalopathy (BSE)
Mad cow disease
Transmissible spongiform encephalopathies
What Is Creutzfeldt-Jakob Disease?
Creutzfeldt-Jakob disease (CJD) is a very rare disorder that damages the tissues of the brain, causing a rapid decline in mental function and muscle coordination, eventually leading to death. It is believed that a tiny transmissible * protein particle called a prion triggers the disease, which is divided into three categories:
- Familial CJD accounts for up to about 10 percent of cases. In these instances, there exists a family history of the disease, suggesting that certain genes * shared by family members make them more susceptible to CJD.
- Sporadic cases, in which people have no known risk factors for the disease, make up about 85 percent of occurrences.
- Acquired CJD is the rarest form. Less than 5 percent of all cases result from exposure to infected brain or spinal tissue, usually during a medical procedure.
CJD belongs to a family of illnesses known as transmissible spongiform (SPUN-jih-form) encephalopathies (en-seh-fuh-LAH-puh-theez). Spongiform refers to the appearance of brain tissue affected by the disease—the damaged tissue is full of holes, much like a sponge. Other diseases in the CJD family include kuru * ; bovine spongiform encephalopathy (BSE), which infects cattle and is known as mad cow disease; and scrapie * , which affects sheep. The disease generally affects people age 60 or older, but in 1996 scientists described a new form of CJD, called variant CJD or new variant CJD (vCJD). Variant CJD differs from classic CJD in that it typically affects people under the age of 30 and causes different symptoms. So far, cases of vCJD have been limited mostly to the United Kingdom and France, and all the people in whom vCJD has developed have been exposed to areas where BSE has been found.
How Common Is CJD?
Creutzfeldt-Jakob disease remains extremely rare, occurring in about one in 1 million people each year.
* transmissible (trans-MIH-sih-bul) means able to be transferred or spread.
* genes (JEENS) are chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.
* kuru (KUR-ew) is a progressive, fatal brain disease characterized by tremors and loss of muscle coordination that is caused by eating contaminated brain tissue from other humans who had the disease.
* scrapie (SKRAY-pee) is a fatal brain disorder of sheep that is characterized by itching of the skin and difficulty walking.
* central nervous system (SEN-trul NER-vus SIS-tem) is the part of the nervous system that includes the brain and spinal cord.
Is the Disease Contagious?
Although CJD may be transmissible, it does not appear to spread through usual types of direct person-to-person contact. CJD can be transmitted through contact with infected brain or central nervous system * tissue or fluid, usually during a medical procedure. For example, the disease has been reported after cornea * transplants and dura mater * grafts * , following injection of human pituitary * -derived growth hormone * , and after contact with medical instruments used during brain surgery on a person with the disease. Cerebrospinal fluid can spread CJD, but there is no evidence of transmission through other body fluids, including saliva, blood, or urine. Variant CJD has occurred only where cases of BSE also have been found, leading researchers to theorize that eating beef from cattle with BSE could spread the agent and lead to CJD in humans. Although this explanation is widely accepted, it has not been proved.
Mad Cow Disease and
the Human Connection
A disease called bovine spongiform encephalopathy (BSE or mad cow disease), which is similar to CJD but is found in cattle, has been linked to variant CJD. Cattle had long been fed ground-up carcasses from sheep and other livestock as a nutritional supplement. This practice may have caused an epidemic of BSE among cows in the United Kingdom that began in 1986. It is thought that the carcasses fed to the cows could have been those of animals infected with various forms of transmissible spongiform disease. In 1988 this feeding practice was banned in the United Kingdom. Millions of cows have since been slaughtered to protect the food supply, and the number of new BSE cases has dropped sharply.
* cornea (KOR-nee-uh) is the transparent circular layer of cells over the central colored part of the eyeball (the iris) through which light enters the eye.
* dura mater (DUR-uh MAY-ter) is the outermost of three membranes covering the brain and spinal cord.
* grafts are tissue or organ transplants.
* microorganisms are tiny organisms that can be seen only using a microscope. Types of microorganisms include fungi, bacteria, and viruses.
* mutation (myoo-TAY-shun) is a change in an organism's gene or genes.
Prions: Are They "Infectious"?
Like bacteria, viruses, and parasites, prions, which are abnormal protein particles, have been linked to certain transmissible diseases. Yet prions are different from other infectious agents. While microorganisms * contain genetic material, prions do not, which means that they are not alive. According to the prion theory, the protein at first cannot transmit disease. Instead, it undergoes a change that allows it to fold into a different shape, its "infectious" form. When a prion enters a brain cell in the course of CJD, it binds to normal proteins, causing them to change shape. This sets off a chain reaction leading to cell death and the release of more prions to enter and affect more cells. As cells die, holes form in brain tissue giving it the characteristic "spongelike" appearance. Prions can be acquired during a medical procedure or from some other exposure to brain tissue or fluids containing brain tissue. In the inherited form of CJD, it is believed that a gene mutation * allows some normal proteins to change into prions under certain conditions.
What Are the Signs and Symptoms of CJD?
The most characteristic symptom of CJD is quickly worsening dementia * , including memory loss and impaired thinking. Patients often have problems with vision and muscle coordination. The inability to sleep, unusual sensations, and depression are also common. Many patients experience muscle jerking known as myoclonus (my-AH-kloh-nus), which consists of brief, rapid muscle contractions. If the disease is contracted from human tissue (such as from a transplanted cornea), symptoms may not appear for decades after exposure to the contaminated tissue. Variant
How Do Doctors Make the Diagnosis?
CJD can be diagnosed by a brain biopsy (BI-op-see), which requires removing a small piece of brain tissue during surgery to examine for signs of the disease, or by an autopsy * . Other, less invasive tests may point to a diagnosis of CJD or help identify another cause of the patient's symptoms, such as meningitis or encephalitis. During a physical examination, the doctor checks for muscle twitching and spasms. An eye exam may show areas of blindness that the patient may not have noticed, and a spinal tap * and blood tests may identify certain proteins associated with CJD. An electroencephalogram (EEG) test records electrical activity in the brain and may show a pattern of brain waves seen in many patients with CJD, although the typical EEG findings are not present in vCJD. Some people with CJD have negative test results, making a diagnosis difficult without a brain biopsy.
* pituitary (pih-TOO-ih-tare-e) is a small ovol-shaped gland at the base of the skull that produces several hormones—substances that affect various body functions, including growth.
* growth hormone is a chemical substance produced by the pituitary gland that regulates growth and other body functions.
* dementia (dih-MEN-sha) is a loss of mental abilities including memory, understanding, and judgment.
* autopsy (AW-top-see) is an examination of a body after death to look for the cause of death or the effects of a disease.
* spinal tap, also called a lumbar puncture, is a medical procedure in which a needle is used to withdraw a sample of the fluid surrounding the spinal cord and brain. The fluid is then tested, usually to detect signs of infection, such as meningitis, or other diseases.
What Is the Treatment and Course of
Because CJD cannot be cured, the goal of treatment is to make the patient as comfortable as possible. Medications can help control aggressive behavior, lessen pain, and ease muscle jerks. Dementia can progress to loss of speech, the inability to take care of oneself, blindness, and even coma. As patients become bedridden, they are vulnerable to infections, such as pneumonia, and most eventually need to be hospitalized. Many patients die within a year after symptoms appear.
How Can CJD Be Prevented?
No known measures can prevent the onset of CJD in a person whose brain tissue contains the prion. Because the ways by which the disease can be transmitted are still not well understood, blood banks forbid people with confirmed or suspected CJD or those who may be at high risk, such as persons with a family history of the disease, to donate blood, and doctors advise that they not be organ or tissue donors. Family members of a person with CJD may wish to have genetic counseling to learn more about any family risk. Special handling of surgical instruments can limit the chance of transmission during certain medical procedures, particularly those involving the brain.
Bacteria to the Rescue
Growth hormone once was obtained from the pituitary glands of cadavers—that is, the bodies of people who have died—and patients who needed injections of growth hormone were at risk of getting CJD. Now growth hormone can be produced in laboratories by inserting the genes controlling the production of growth hormone into bacteria, thus avoiding the need to extract the hormone from human tissue and eliminating the risk of transmitting CJD.
Creutzfeldt-Jakob Disease Foundation, Inc., P.O. Box 5312, Akron, OH
44334. The foundation gives an overview of CJD and lists CJD-related
websites, along with the latest news and research.