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Definition of Creutzfeldt-Jakob disease (CJD)

Creutzfeldt-Jakob disease (CJD): A degenerative, invariably fatal brain disorder. It affects about one person in every one million people per year worldwide; in the United States there are about 200 cases per year. CJD usually appears in later life and runs a rapid course. Typically, onset of symptoms occurs about age 60, and about 90% of patients die within a year. In the early stages of disease, patients may have failing memory, behavioral changes, lack of coordination and visual disturbances. As the illness progresses, mental deterioration becomes pronounced and involuntary movements, blindness, weakness of extremities, and coma may occur.

There are three major categories of CJD:

  • Sporadic CJD: In sporadic CJD, the disease appears even though the person has no known risk factors for the disease. This is by far the most common type of CJD and accounts for at least 85% of cases.
  • Hereditary CJD: In hereditary CJD, the person has a family history of the disease and/or tests positive for a genetic mutation associated with CJD. About 5 to 10% of cases of CJD in the United States are hereditary.
  • Acquired CJD: In acquired CJD, the disease is transmitted by exposure to brain or nervous system tissue, usually through certain medical procedures. There is no evidence that CJD is contagious through casual contact with a CJD patient. Since CJD was first described in 1920, fewer than 1% of cases have been acquired CJD.

CJD belongs to a family of human and animal diseases known as the transmissible spongiform encephalopathies (TSEs). Spongiform refers to the characteristic appearance of infected brains, which become filled with holes until they resemble sponges under a microscope. CJD is the most common of the known human TSEs. Other human TSEs include kuru, fatal familial insomnia (FFI), and Gerstmann-Straussler-Scheinker disease (GSS). Kuru was identified in people of an isolated tribe in Papua New Guinea and has now almost disappeared. Fatal familial insomnia and GSS are extremely rare hereditary diseases, found in just a few families around the world. Other TSEs are found in specific kinds of animals. These include bovine spongiform encephalopathy (BSE), which is found in cows and often referred to as "mad cow" disease, scrapie, which affects sheep and goats, mink encephalopathy, and feline encephalopathy. Similar diseases including chronic wasting disease (CWD) occur in elk, deer, and exotic zoo animals.

Symptoms: CJD is a rapidly progressive dementia. Initially, patients experience problems with muscular coordination; personality changes, including impaired memory, judgment, and thinking; and impaired vision. People with the disease also may experience insomnia, depression, or unusual sensations. CJD does not cause a fever or other flu-like symptoms. As the illness progresses, the patients' mental impairment becomes severe. They often develop involuntary muscle jerks called myoclonus, and they may go blind. They eventually lose the ability to move and speak and enter a coma. Pneumonia and other infections often occur in these patients and can lead to death.

There are several known variants of CJD. These variants differ somewhat in the symptoms and course of the disease. For example, a variant form of the disease -- called new variant or variant (nv-CJD or v-CJD), described in Great Britain and France -- begins primarily with psychiatric symptoms, affects younger patients than other types of CJD, and has a longer than usual duration from onset of symptoms to death. Another variant, called the panencephalopathic form, occurs primarily in Japan and has a relatively long course, with symptoms often progressing for several years. CJD causes unique changes in brain tissue which can be seen at autopsy.

Diagnosis: There is currently no single diagnostic test for CJD. When CJD is suspected, the first concern is to rule out treatable forms of dementia such as encephalitis (inflammation of the brain) or chronic meningitis. A neurological examination and spinal tap are often performed to rule out more common causes of dementia. An electroencephalogram (EEG) to record the brain's electrical pattern can be particularly valuable because it shows a specific type of abnormality in CJD. Computerized tomography (CT) of the brain can help rule out the possibility that the symptoms result from other problems such as stroke or a brain tumor. Magnetic resonance imaging (MRI) brain scans also can reveal characteristic patterns of brain degeneration that can help diagnose CJD.

At present, the only sure way to confirm a diagnosis of CJD is by brain biopsy or autopsy. In a brain biopsy, a neurosurgeon removes a small piece of tissue from the patient's brain so that it can be examined by a neuropathologist. This procedure may be dangerous for the patient, and the operation does not always obtain tissue from the affected part of the brain. Because a correct diagnosis of CJD does not help the patient, a brain biopsy is discouraged unless it is needed to rule out a treatable disorder. In an autopsy, the whole brain is examined after death. More tests for CJD are under development.

Treatment: There is no treatment that can cure or control CJD. Researchers have tested many drugs, including amantadine, steroids, interferon, acyclovir, antiviral agents, and antibiotics. However, none of these treatments has shown any consistent benefit. Current treatment for CJD is aimed at alleviating symptoms and making the patient as comfortable as possible.

Cause(s): The agent that causes CJD has several characteristics that are unusual for well-known organisms such as viruses and bacteria. It is difficult to kill, it does not appear to contain any genetic information in the form of nucleic acids (DNA or RNA), and it usually has a long incubation period before symptoms appear. In some cases, the incubation period may be as long as 40 years. The leading scientific theory at this time maintains that CJD and the other TSEs are caused not by an organism but by a type of protein called a "prion."

Prions occur in both a normal form, which is a harmless protein found in the body's cells; and in an infectious form, which causes disease. The harmless and infectious forms of the prion protein are nearly identical, but the infectious form takes a different folded shape than the normal protein. Sporadic CJD may develop because some of a person's normal prions spontaneously change into the infectious form of the protein and then alter the prions in other cells in a chain reaction.

Once they appear, abnormal prion proteins stick together and form fibers and/or clumps called plaques that can be seen with powerful microscopes. Fibers and plaques may start to accumulate years before symptoms of CJD begin to appear. It is still unclear what role these abnormalities play in the disease or how they might affect symptoms.

About 5 to 10% of all CJD cases are inherited. These cases arise from a mutation, or change, in the gene that controls formation of the normal prion protein. While prions themselves do not contain genetic information and do not require genes to reproduce themselves, infectious prions can arise if a mutation occurs in the gene for the body's normal prions. If the prion gene is altered in a person's sperm or egg cells, the mutation can be transmitted to the person's offspring. Several different mutations in the prion gene have been identified. The particular mutation found in each family affects how frequently the disease appears and what symptoms are most noticeable. However, not all people with mutations in the prion gene develop CJD. This suggests that the mutations merely increase susceptibility to CJD and that other, still-unknown factors also play a role in the disease.

Transmission: CJD is not a contagious disease in the usual sense. Although it can be transmitted to other people, the risk of this happening is extremely small. CJD cannot be transmitted through the air or through touching or most other forms of casual contact. Spouses and other household members of sporadic CJD patients have no higher risk of contracting the disease than the general population. However, direct or indirect contact with brain tissue and spinal cord fluid from infected patients should be avoided to prevent transmission of the disease through these materials.

In a few very rare cases, CJD has spread to other people from grafts of dura mater (a tissue that covers the brain), transplanted corneas, implantation of inadequately sterilized electrodes in the brain, and injections of contaminated pituitary growth hormone derived from human pituitary glands taken from cadavers. Doctors call these cases that are linked to medical procedures iatrogenic cases. Since 1985, all human growth hormone used in the U.S. has been synthesized by recombinant DNA procedures, which eliminates the risk of transmitting CJD by this route.

The appearance of the new variant of CJD (nv-CJD or v-CJD) in several younger than average people in Great Britain and France has led to concern that BSE may be transmitted to humans through consumption of contaminated beef. Although laboratory tests have shown a strong similarity between the prions causing BSE and v-CJD, there is no direct proof to confirm this theory. Furthermore, BSE has never been found in the U.S., and importation of cattle and beef from countries with BSE has been banned in the U.S. since 1989 to reduce the risk that it will occur in this country.

Some animal studies suggest that contaminated blood and related products may transmit the disease, although this has never been shown in humans. If there are infectious agents in these fluids, they are probably in very low concentrations. Scientists do not know how many abnormal prions a person must receive before he or she develops CJD, so they do not know whether these fluids are potentially infectious or not. They do know that, even though millions of people receive blood transfusions each year, there are no reported cases of someone contracting CJD from a transfusion. Even among hemophiliacs, who sometimes receive blood plasma concentrated from thousands of people, there are no reported cases of CJD. This suggests that, if there is a risk of transmitting CJD through blood or plasma, it is extremely small.

Precautions: To reduce the already very low risk of CJD transmission from one person to another, people should never donate blood, tissues, or organs if they have suspected or confirmed CJD, or if they are at increased risk because of a family history of the disease, a dura mater graft, or other factor.

Normal sterilization procedures such as cooking, washing, and boiling do not destroy prions. Caregivers, health care workers, and undertakers should take the following precautions when they are working with a person with CJD:

  • Wash hands and exposed skin before eating, drinking, or smoking.
  • Cover cuts and abrasions with waterproof dressings.
  • Wear surgical gloves when handling a patient's tissues and fluids or dressing the patient's wounds.
  • Avoid cutting or sticking themselves with instruments contaminated by the patient's blood or other tissues.
  • Use disposable bedclothes and other cloth for contact with the patient.
  • If disposable materials are not available, regular cloth should be soaked in undiluted chlorine bleach for an hour or more, then washed in a normal fashion after each use.
  • Use face protection if there is a risk of splashing contaminated material such as blood or cerebrospinal fluid.
  • Soak instruments that have come in contact with the patient in undiluted chlorine bleach for an hour or more, then use an autoclave (pressure cooker) to sterilize them in distilled water for at least one hour at 132 - 134 degrees Centigrade.

Source: MedTerms™ Medical Dictionary
http://www.medicinenet.com/script/main/art.asp?articlekey=2863
Last Editorial Review: 6/14/2012

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