|Classification and external resources|
Tonsil biopsy in variant CJD. Prion protein immunostaining.
Creutzfeldt–Jakob disease (pron.: / / KROITS-felt YAH-kohb) or CJD is a degenerative neurological disorder (brain disease) that is incurable and invariably fatal. CJD is at times called a human form of mad cow disease (bovine spongiform encephalopathy or BSE) even though classic CJD is not related to BSE; however, given that BSE is believed to be the cause of variant Creutzfeldt–Jakob (vCJD) disease in humans, the two are often confused.
In CJD, the brain tissue develops holes and takes on a sponge-like texture. This is due to a type of infectious protein called a prion. Prions are misfolded proteins which replicate by converting their properly folded counterparts.
Types of CJD include:
The first symptom of CJD is rapidly progressive dementia, leading to memory loss, personality changes and hallucinations. This is accompanied by physical problems such as speech impairment, jerky movements (myoclonus), balance and coordination dysfunction (ataxia), changes in gait, rigid posture, and seizures. The duration of the disease varies greatly, but sporadic (non-inherited) CJD can be fatal within months or even weeks (Johnson, 1998). In some people, the symptoms can continue for years. In most patients, these symptoms are followed by involuntary movements and the appearance of an atypical diagnostic electroencephalogram tracing. Most victims die six months after initial symptoms appear, often of pneumonia due to impaired coughing reflexes. About 15% of patients survive two or more years.
The symptoms of CJD are caused by the progressive death of the brain's nerve cells, which is associated with the build-up of abnormal prion proteins forming amyloids. When brain tissue from a CJD patient is examined under a microscope, many tiny holes can be seen where whole areas of nerve cells have died. The word "spongiform" in "transmissible spongiform encephalopathies" refers to the sponge-like appearance of the brain tissue.
Transmissible spongiform encephalopathy diseases are caused by prions. The diseases are thus sometimes called prion diseases. Other prion diseases include Gerstmann–Sträussler–Scheinker syndrome (GSS), fatal familial insomnia (FFI) and kuru in humans, as well as bovine spongiform encephalopathy (BSE, commonly known as mad cow disease) in cattle, chronic wasting disease (CWD) in elk and deer, and scrapie in sheep. Alpers' syndrome in infants is also thought to be a transmissible spongiform encephalopathy caused by a prion.
The prion that is believed to cause Creutzfeldt–Jakob exhibits at least two stable conformations. One, the native state, is water-soluble and present in healthy cells. As of 2007[update], its biological function is presumably in transmembrane transport or signaling. The other conformational state is relatively water-insoluble and readily forms protein aggregates.
People can also acquire CJD genetically through a mutation of the gene that codes for the prion protein (PRNP). This occurs in only 5–10% of all CJD cases.
The CJD prion is dangerous because it promotes refolding of native proteins into the diseased state. The number of misfolded protein molecules will increase exponentially and the process leads to a large quantity of insoluble protein in affected cells. This mass of misfolded proteins disrupts cell function and causes cell death. Mutations in the gene for the prion protein can cause a misfolding of the dominantly alpha helical regions into beta pleated sheets. This change in conformation disables the ability of the protein to undergo digestion. Once the prion is transmitted, the defective proteins invade the brain and are produced in a self-sustaining feedback loop.
Stanley B. Prusiner of the University of California, San Francisco (UCSF) was awarded the Nobel Prize in physiology or medicine in 1997 "for his discovery of Prions - a new biological principle of infection". For more than a decade, Yale University neuropathologist Laura Manuelidis has been challenging this explanation for the disease. In January 2007, she and her colleagues published an article in the Proceedings of the National Academy of Science and reported that they have found a virus-like particle (but without finding nucleic acids so far) in less than 10% of the cells in a scrapie-infected cell line and in a mouse cell line infected by a human CJD agent.
The defective protein can be transmitted by contaminated harvested human brain products, immunoglobulins (IVIG), corneal grafts, dural grafts or electrode implants (acquired or iatrogenic form: iCJD); it can be inherited (hereditary or familial form: fCJD); or it may appear for the first time in the patient (sporadic form: sCJD). In the hereditary form, a mutation occurs in the gene for PrP, PRNP. Ten to 15 percent of CJD cases are inherited. (CDC)
The disease has also been shown to result from use of human growth hormone obtained from the pituitary glands of persons who died from Creutzfeldt–Jakob Disease, though the known incidence of this cause is (as of April 2004) quite small. The risk of infection via cadaveric HGH in the US ceased when the medication was withdrawn in 1985.
It is thought that humans can contract the disease by consuming material from animals infected with the bovine form of the disease. The only suspected cases to arise thus far have been vCJD with the vast majority of these cases being in the UK, moreover there are fears—based on animal studies—that consuming beef or beef products containing prion particles can also cause the development of classic CJD. When BSE material infects humans, the resulting disease is known as (new) variant CJD (nvCJD).
Cannibalism has also been implicated as a transmission mechanism for abnormal prions, causing the disease known as kuru, once found primarily among women and children of the Fore people in Papua New Guinea. While the men of the tribe ate the body of the deceased and rarely contracted the disease, the women and children, who ate the less desirable body parts, including the brain, were 8 times more likely than men to contract kuru from infected tissue.
Prions, the infectious agent of CJD, may not be inactivated by means of routine surgical instrument sterilization procedures. The World Health Organization and the US Centers for Disease Control and Prevention recommend that instrumentation used in such cases be immediately destroyed after use; short of destruction, it is recommended that heat and chemical decontamination be used in combination to process instruments that come in contact with high-infectivity tissues. No cases of iatrogenic transmission of CJD have been reported subsequent to the adoption of current sterilization procedures, or since 1976. Copper–hydrogen peroxide has been suggested as an alternative to the current recommendation of sodium hydroxide or sodium hypochlorite. Thermal depolymerization also destroys prions in infected organic and inorganic matter, since the process chemically attacks protein at the molecular level, although more effective and practical methods involve destruction by combinations of detergents and enzymes similar to biological washing powders.
In 2004 a new report published in the Lancet medical journal showed that vCJD can be transmitted by blood transfusions. The finding alarmed healthcare officials because a large epidemic of the disease could result in the near future. A blood test for vCJD infection is possible but has not been developed for screening blood donations and significant restrictions exist to protect the blood supply. The UK government banned anyone who had received a blood transfusion since January 1980 from donating blood. From 1999 there has been a ban in the UK for using UK blood to manufacture fractional products such as albumin.
On May 28, 2002, the United States Food and Drug Administration instituted a policy that excludes from donation anyone who spent at least six months in certain European countries, (or three months in the United Kingdom), from 1980 to 1996. Given the large number of U.S. military personnel and their dependents residing in Europe, it was expected that over 7% of donors would be deferred due to the policy. Later changes to this policy have relaxed the restriction to a cumulative total of five years or more of civilian travel in European countries (six months or more if military). The three-month restriction on travel to the UK, however, has not been changed.
The American Red Cross' policy is as follows: During the period January 1, 1980, to December 31, 1996, spending a total time of three months or more in the Channel Islands, England, the Falkland Islands, the Isle of Man, Gibraltar, Northern Ireland, Scotland, and Wales precludes individuals from donating. Moreover, spending a total time of five years or more after January 1, 1980 (to present), in the above-mentioned countries and/or any country in Europe (except the former USSR), also precludes donation. People with a biologic relative who has been diagnosed with CJD or vCJD are unable to donate. Biologic relative in this setting means mother, father, sibling, grandparent, aunt, uncle or children.
A similar policy applies to potential donors to the Australian Red Cross' Blood Service, precluding people who have spent a cumulative time of six months or more in the United Kingdom between 1980 and 1996.
The Singapore Red Cross precludes potential donors who have spent a cumulative time of three months or more in the United Kingdom between 1980 and 1996.
In New Zealand, the New Zealand Blood Service (NZBS) in 2000 introduced measures to preclude permanently donors who had resided in the United Kingdom (including the Isle of Man and the Channel Islands) for a total of six months or more between January 1980 and December 1996. The measure resulted in ten percent of New Zealand's active blood donors at the time to become ineligible to donate blood. In 2003, the NZBS further extended restrictions to preclude permanently donors who had received a blood transfusion in the United Kingdom since January 1980, and in April 2006, restrictions were further extended to include the Republic of Ireland and France.
Similar regulations are in place in Germany, where anyone who has spent six months or more living in the UK between January 1980 and December 1996 is permanently banned from donating blood.
As of 1999, Health Canada announced a policy to defer individuals from donating blood if they have lived within the United Kingdom for one month or more from January 1, 1980, to December 31, 1996. In 2000, the same policy was applied to people who have resided in France, for at least three months from January 1980 to December 1996. Canada will not accept blood from a person who has spent more than six months in a Western European country since January 1, 1980.
The Association of Blood Donors of Denmark precludes potential donors who have spent a cumulative time of at least 12 months in the United Kingdom between 1 January 1980 and 31 December 1996.
The Swiss Blutspendedienst SRK precludes potential donors who have spent a cumulative time of at least six months in the United Kingdom between 1 January 1980 and 31 December 1996.
In Poland, anyone who cumulatively spent six months or longer between 1 January 1980 and 31 December 1996 in the UK, Ireland or France is permanently barred from donating.
In the Czech Republic, anyone who spent more than six months in the UK or France between the years 1980 and 1996 or received transfusion in the UK after the year 1980 is not allowed to donate blood.
In the U.S., the FDA has banned import of any donor sperm, motivated by a risk of Creutzfeldt–Jakob disease, inhibiting the once popular import of, for example, Scandinavian sperm. The risk, however, is not known, since artificial insemination has not been studied as a route of transmission.
The diagnosis of CJD is suspected when there are typical clinical symptoms and signs such as rapidly progressing dementia with myoclonus. Further investigation can then be performed to support the diagnosis including
Diffusion Weighted Imaging (DWI) images are the most sensitive. In about 24% of cases DWI shows only cortical hyperintensity; in 68%, cortical and subcortical abnormalities; and in 5%, only subcortical anomalies. The involvement of the thalamus can be found in sCJD, is even stronger and constant in vCJD.
Clinical testing for CJD has always been an issue. Diagnosis has mostly been based on clinical and physical examination of symptoms. In recent years, studies have shown that the tumour marker Neuron-specific enolase (NSE) is often elevated in CJD cases, however its diagnostic utility is primarily seen when combined with a test for the 14-3-3 protein. As of 2010[update], screening tests to identify infected asymptomatic individuals, such as blood donors, are not yet available, though methods have been proposed and evaluated.
In 2010, a team from New York described detection of PrPSc even when initially present at only one part in one hundred billion (10−11) in brain tissue. The method combines amplification with a novel technology called surround optical fiber immunoassay (SOFIA) and some specific antibodies against PrPSc. After amplifying and then concentrating any PrPSc, the samples are labelled with a fluorescent dye using an antibody for specificity and then finally loaded into a micro-capillary tube. This tube is placed in a specially constructed apparatus so that it is totally surrounded by optical fibres to capture all light emitted once the dye is excited using a laser. The technique allowed detection of PrPSc after many fewer cycles of conversion than others have achieved, substantially reducing the possibility of artefacts, as well as speeding up the assay. The researchers also tested their method on blood samples from apparently healthy sheep that went on to develop scrapie. The animals’ brains were analysed once any symptoms became apparent. The researchers could therefore compare results from brain tissue and blood taken once the animals exhibited symptoms of the diseases, with blood obtained earlier in the animals’ lives, and from uninfected animals. The results showed very clearly that PrPSc could be detected in the blood of animals long before the symptoms appeared. After further development and testing, this method could be of great value in surveillance as a blood or urine-based screening test for CJD.
In one third of patients with sporadic CJD, deposits of "prion protein (scrapie)," PrPSc, can be found in the skeletal muscle and/or the spleen. Diagnosis of vCJD can be supported by biopsy of the tonsils, which harbour significant amounts of PrPSc; however, biopsy of brain tissue is the definitive diagnostic test. Due to its invasiveness, biopsy will not be done if clinical suspicion is sufficiently high or low. A negative biopsy does not rule out CJD, since it may predominate in a specific part of the brain
The classic histologic appearance is spongiform change in the gray matter: the presence of many round vacuoles from one to 50 micrometres in the neuropil, in all six cortical layers in the cerebral cortex or with diffuse involvement of the cerebellar molecular layer. These vacuoles appear glassy or eosinophilic and may coalesce. Neuronal loss and gliosis are also seen. Plaques of amyloid-like material can be seen in the neocortex in new-variant CJD.
Unfortunately, vacuolization can be seen in other disease states. Diffuse cortical vacuolization occurs in Alzheimer's, and superficial cortical vacuolization occurs in ischemia and frontotemporal dementia. These vacuoles appear clear and punched-out. Larger vacuoles encircling neurons, vessels, and glia are a possible processing artifact.
|Characteristic||Classic CJD||Variant CJD|
|Median age at death||68 years||28 years|
|Median duration of illness||4–5 months||13–14 months|
|Clinical signs and symptoms||Dementia; early neurologic signs||Prominent psychiatric/behavioral symptoms; painful dysesthesias;
delayed neurologic signs
|Periodic sharp waves on electroencephalogram||Often present||Often absent|
|Signal hyperintensity in the caudate nucleus and putamen on diffusion-weighted and FLAIR MRI||Often present||Often absent|
|Pulvinar sign-bilateral high signal intensities on axial fluid attenuated inversion recovery (FLAIR) MRI. Also posterior thalami involvement on sagittal T2 sequences||Not reported||Present in >75% of cases|
|Immunohistochemical analysis of brain tissue||Variable accumulation.||Marked accumulation of protease-resistant prion protein|
|Presence of agent in lymphoid tissue||Not readily detected||Readily detected|
|Increased glycoform ratio on immunoblot analysis of
protease-resistant prion protein
|Not reported||Marked accumulation of protease-resistant prion protein|
|Presence of amyloid plaques in brain tissue||May be present||May be present|
As of 2011[update] no generally accepted treatment for CJD exists; the disease is invariably fatal and research continues. An experimental treatment was given to a Northern Irish teenager, Jonathan Simms, beginning in January 2003. The medication, called pentosan polysulphate (PPS) and used to treat interstitial cystitis, is infused into the patient's lateral ventricle within the brain. PPS does not seem to stop the disease from progressing, and both brain function and tissue continue to be lost. However, the treatment is alleged to slow the progression of the otherwise untreatable disease, and may have contributed to the longer than expected survival of the seven patients who were studied. Simms died in 2011. The CJD Therapy Advisory Group to the UK Health Departments advises that data are not sufficient to support claims that pentosan polysulphate is an effective treatment and suggests that further research in animal models is appropriate. A 2007 review of the treatment of 26 patients with PPS finds no proof of efficacy because of the lack of accepted objective criteria.
Scientists have investigated using RNA interference to slow the progression of scrapie in mice. The RNA blocks production of the protein that the CJD process transforms into prions. This research is unlikely to lead to a human therapy for many years.
Both amphotericin B and doxorubicin have been investigated as potentially effective against CJD, but as yet there is no strong evidence that either drug is effective in stopping the disease. Further study has been taken with other medical drugs, but none are effective. However, drugs to reduce suffering do exist, and include Valproate, an anticonvulsant agent, and Clonazepam an benzodiazepine, to reduce muscle jerks.
Dr. Michael Geschwind, Dr. Bruce Miller and Dr. Stanley Prusiner from University of California, San Francisco are currently running a treatment trial for sporadic CJD using quinacrine, a medicine originally created for malaria. Pilot studies showed quinacrine permanently cleared abnormal prion proteins from cell cultures, but results have not yet been published on the clinical study.
Although CJD is the most common human prion disease, it is still rare, occurring in about one out of every one million people every year. It usually affects people aged 45–75, most commonly appearing in people between the ages of 60–65. The exception to this is the more recently-recognised 'variant' CJD (vCJD), which occurs in younger people.
CDC monitors the occurrence of CJD in the United States through periodic reviews of national mortality data. According to the CDC:
In The Lancet (June 2006), a University College London team suggested that it may take more than 50 years for vCJD to develop, from their studies of kuru, a similar disease in Papua New Guinea. The reasoning behind the claim is that kuru was possibly transmitted through cannibalism in Papua New Guinea when family members would eat the body of a dead relative as a sign of mourning. In the 1950s, cannibalism was banned in PNG.
In the late 20th century, however, kuru reached epidemic proportions in certain Papua New Guinean communities, therefore suggesting that vCJD may also have a similar incubation period of 20 to 50 years. A critique to this theory is that while mortuary cannibalism was banned in Papua New Guinea in the 1950s, that does not necessarily mean that the practice ended. 15 years later Jared Diamond was informed by Papuans that the practice continued. Kuru may have passed to the Fore people through the preparation of the dead body for burial.
These researchers noticed a genetic variation in some kuru patients that has been known to promote long incubation periods. They have also proposed that individuals who contracted CJD in the early 1990s represent a distinct genetic subpopulation, with unusually short incubation periods for bovine spongiform encephalopathy (BSE). This means that there may be many more vCJD patients who have longer incubation periods, which may surface many years later.
In 1997 a number of Kentuckians developed CJD. It was discovered that all the victims had consumed squirrel brains, although a coincidental relationship between the disease and this dietary practice may have been involved. UK scientists have recently expressed concern over the possibility of a second wave of human cases due to the wide exposure and long incubation of some cases of vCJD.
The disease was first described by German neurologist Hans Gerhard Creutzfeldt in 1920 and shortly afterwards by Alfons Maria Jakob, giving it the name Creutzfeldt–Jakob. Some of the clinical findings described in their first papers do not match current criteria for Creutzfeldt–Jakob disease, and it has been speculated that at least two of the patients in initial studies were suffering from a different ailment. An early description of familial CJD stems from the German psychiatrist and neurologist Friedrich Meggendorfer (1880–1953).
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|リンク元||「クロイツフェルト・ヤコブ病」「脳炎」「subacute spongiform encephalopathy」「CJD」「Creutzfeld-Jakob disease」|
|拡張検索||「new variant Creutzfeldt-Jakob disease」「familial Creutzfeldt-Jakob disease」|