What is Creutzfeldt-Jakob disease?
Creutzfeldt-Jakob disease (CJD) is a rare, fatal brain disorder caused by a prion. The disease causes mental deterioration and a variety of neurological symptoms, and usually leads to death within a year of onset.
Threre are various forms of CJD; in about 85 percent of the cases, the cause is unknown. One form of CJD may be linked to consumption of beef in Great Britain. Another form is familial or genetic, that is, relatives of a CJD case with the form are more likely to develop the disease than other persons. Many Americans first heard of the disease in 1983 when they learned it had claimed the life of New York City Ballet choreographer George Balanchine.
How does CJD affect the patient?
In early stages of the disease, patients may experience failing memory, changes in behavior, lack of coordination or visual disturbances. As the illness progresses, mental deterioration becomes pronounced, involuntary movements (especially muscle jerks) appear, and the patient may become blind, develop weakness in the arms or legs, and ultimately lapse into a coma. Death is usually due to infections in the bedridden, unconscious patient.
Symptoms of CJD can be similar to those seen in other progressive neurological disorders such as Alzheimer's disease and other dementias. However, CJD causes unique changes in brain tissue that, at this time, can be detected only by surgical biopsy or at autopsy.
Who gets CJD?
The disease afflicts men and women of diverse ethnic backgrounds, appearing most often in those 50 to 75 years of age. Internationally, there is one CJD case per year for every million people.
An estimated 200 Americans die each year with Creutzfeldt-Jakob disease. National data indicate the annual CJD mortality rates in the United States between 1979 and 1993 remained relatively stable, ranging between 0.8 cases per million in both 1979 and 1990 and 1.1 cases per million in 1987.
What causes CJD?
Scientists agree that a prion that is transmissible causes Creutzfeldt-Jakob disease, but this agent has not yet been fully identified.
A prion is a protein comprising a specific sequence of amino acids. It is neither a virus nor any other previously known infectious agent, but rather an unconventional agent. Prions are thought to transform normal, benign protein molecules into deadly ones by altering their shape.
What is the connection between CJD and beef?
In 1996, officials in Great Britain announced that 10 cases of a previously unrecognized form of CJD had been identified and might be linked to consumption of beef from cattle with bovine spongiform encephalopathy (BSE), a disease that affected more than 177,500 cattle in that country from 1986 through 2000. British officials emphasized that current evidence is insufficient to establish a direct link between BSE and this new variant of CJD; however, such an association offers the most likely explanation for the occurrence of this cluster of cases. BSE has not been found in cattle in the United States, and beef and cattle from Great Britain cannot be imported into this country. More than 5,000 U.S. cattle that died of neurological disease have been tested and all were negative for BSE.
Is CJD contagious?
The low incidence of Creutzfeldt-Jakob disease indicates person-to-person transmission is rare. Spouses of patients and other household members have no higher risk of contracting the disorder than the general population.
There is evidence, however, that the prion can be introduced into the nervous systems of healthy persons during certain medical procedures, including corneal transplants. Creutzfeldt-Jakob disease also has been accidentally transmitted through implantation of contaminated electrodes in the brain. Clusters of Creutzfeldt-Jakob cases have been documented among patients undergoing neurosurgery at a few medical facilities.
In 1984 and 1985, at least four patients who had received human growth hormone to correct growth deficiencies died from CJD. Scientists suspect several batches of hormone, derived from human pituitary tissue, were contaminated by the Creutzfeldt-Jakob prion. The use of natural human growth hormone has been discontinued in the United States and Great Britain, and drug companies now are marketing a synthetic form of the hormone to avoid any possibility of such contamination.
Are health professionals at risk of contracting the disease?
In a few instances, CJD has occurred among physicians, dentists and other health care workers, possibly after having been exposed to the agent in the course of their work. However, the incidence of the disease in health care workers is not higher than in the remainder of the population. Health care professionals would be wise to take precautions when handling blood and spinal fluid samples taken from patients with CJD. Scientists recommend that health care workers —
- be careful not to cut or puncture themselves when using instruments contaminated by a patient's blood or spinal fluid,
- wear gloves when handling a patient's tissues and fluids, and
- use special decontamination techniques for instruments that have come in contact with a suspected patient's tissues (the use of disposable neurosurgical instruments should be considered.).
Is there any treatment for CJD?
No effective treatment for Creutzfeldt-Jakob disease is known. Drugs now are being evaluated against the laboratory-induced disease in rodents and nonhuman primates, but none has shown evidence of lasting benefit.
Currently, clinical studies include tests of antiviral drugs, such as amantadine, a compound useful in parkinsonism. Some patients taking these drugs have experienced brief periods of improvement and treatment has not proven harmful. To date, however, drugs have neither controlled nor cured the disease.