Գլխավոր Հիվանդություններ Creutzfeldt–Jakob disease

Creutzfeldt–Jakob disease (CJD) is a degenerative neurological disease that is incurable and invariably fatal. CJD is at times called a human form of mad cow disease (bovine spongiform encephalopathy or BSE). However, given that BSE is believed to be the cause of Variant Creutzfeldt–Jakob disease (vCJD) in humans, the two are often confused. CJD is caused by an infectious agent called a prion. Prions are misfolded proteins that replicate by converting their properly folded counterparts, in their host, to the same misfolded structure they possess. CJD causes the brain tissue to degenerate rapidly, and as the disease destroys the brain, the brain develops holes and the texture changes to resemble that of a kitchen sponge. Signs and symptoms The first symptom of CJD is rapidly progressive dementia, leading to memory loss, personality changes, and hallucinations. Other frequently occurring features include anxiety, depression, paranoia, obsessive-compulsive symptoms, and psychosis. 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. In most patients, these symptoms are followed by involuntary movements and the appearance of an atypical diagnostic electroencephalogram tracing. The duration of the disease varies greatly, but sporadic (non-inherited) CJD can be fatal within months or even weeks.[citation needed] Most victims die six months after initial symptoms appear, often of pneumonia due to impaired coughing reflexes. About 15% of patients survive for two or more years. Some patients have been known to live four to five years with mostly psychological symptoms while the disease progresses. It then causes more physical symptoms that lead to diagnosis, after which death usually occurs within a year. 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.

Cause Transmissible spongiform encephalopathy diseases are caused by prions. Prions are proteins that occur normally in neurons of the central nervous system (CNS). As of 2007, these proteins are thought to affect signaling processes, damaging neurons and resulting in degeneration that causes the spongiform appearance in the affected brain. 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 neuronal 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. These neurodegenerative diseases are commonly called prion diseases. 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. An EU study determined that 87% of cases were sporadic, 8% genetic, and 5% iatrogenic. Transmission The defective protein can be transmitted by contaminated harvested human brain products,corneal grafts (in at least one reported case), dural grafts or electrode implants (acquired or iatrogenic form (iCJD)); it can be familial (fCJD); or it may appear for the first time in the patient (sporadic form: sCJD). In the familial form, a mutation occurs in the gene for PrP, PRNP. Ten to fifteen percent of CJD cases are familial. (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 cases in the UK and Canada. But there are also 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 eight 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. Blood donor restrictions In 2004, a 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 is not yet available for screening blood donations. 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.[29] Whilst these restrictions may go some way to preventing a self-sustaining epidemic of secondary infections the number of infected blood donations is unknown and could be considerable as a study by the Health Protection Agency show around 1 in 2000 people in the UK shows signs of abnormal prion accumulation.[30] In June 2013 the government was warned that deaths—then at 176—could rise five-fold through blood transfusions. On May 28, 2002, the United States Food and Drug Administration instituted a policy that excludes from donation anyone having 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 United Kingdom, Channel Islands, the Falkland Islands and Gibraltar 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 having been diagnosed with CJD or vCJD are unable to donate. Biologic relative in this setting means mother, father, sibling, grandparent, aunt, uncle, or child. 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 having 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 having 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 becoming ineligible to donate blood. In 2003, the NZBS further extended restrictions to preclude permanently donors having 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 France and in Germany, where anyone having spent six months or more living in the UK between January 1980 and December 1996 is permanently banned from donating blood. In Canada, individuals are not eligible to donate blood or plasma if they have spent a cumulative total of three months or more in the United Kingdom (UK) or France from January 1, 1980, to December 31, 1996. They are also ineligible if they have spent a cumulative total of five years or more in Western Europe outside the U.K. or France since January 1, 1980 through December 31, 2007 or Spent a cumulative total of six months or more in Saudi Arabia from January 1, 1980 through December 31, 1996 or if they have had a blood transfusion in the U.K., France or Western Europe since 1980. The Association of Blood Donors of Denmark precludes potential donors having 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 having spent a cumulative time of at least six months in the United Kingdom between 1 January 1980 and 31 December 1996. In Poland, anyone having spent cumulatively 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 having 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 South Korea, anyone having spent more than three months in the UK after 1997, or more than a month between 1980 and 1996 is banned from donating blood.

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