Creutzfeldt-Jakob disease

Synonyms

1

Overview

Creutzfeldt–Jakob disease  or 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 (vCJD) disease in humans, the two are often confused.

CJD is caused by an 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.

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. The duration of the disease varies greatly, but sporadic (non-inherited) CJD can be fatal within months or even weeks. 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 for two or more years. Some patients have been known to live 4–5 years with mostly psychological symptoms until the disease progresses causing more physical symptoms leading to a diagnosis and inevitable death usually within the first year of diagnosis.

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.

Causes

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. 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 vCJD infection. 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 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 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 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 in the United Kingdom 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 1980, 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.

Sperm donor restrictions

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 Scandinavian sperm. The risk, however, is not known, since artificial insemination has not been studied as a route of transmission.

Prevention

There is no known way to prevent sporadic CJD. If you have a family history of neurological disease, you may benefit from talking with a genetics counselor, who can help you sort through the risks associated with your situation.

Preventing iatrogene CJD

Hospitals and other medical institutions follow explicit policies to prevent iatrogenic CJD. These measures have included:

  • Exclusive use of synthetic human growth hormone, rather than the kind derived from human pituitary glands
  • Destruction of surgical instruments used on the brain or nervous tissue of someone with known or suspected CJD
  • Single-use kits for spinal taps (lumbar punctures).

To help ensure the safety of the blood supply, people with a risk of exposure to CJD or vCJD aren't eligible to donate blood. This includes people who:

  • Have a biological relative who has been diagnosed with CJD
  • Have received a dura mater brain graft
  • Have received human growth hormone
  • Spent at least three months in the United Kingdom from 1980 to 1996
  • Spent five years or more in France since 1980
  • Received a blood transfusion in the U.K. since 1980
  • Have injected bovine insulin since 1980.

Preventing vCJD

The risk of contracting vCJD in the United States remains extremely low. Only three cases have been reported in the U.S. According to the Centers for Disease Control and Prevention, strong evidence suggests that these cases were acquired abroad — two in the United Kingdom and one in Saudi Arabia.

In the United Kingdom, where the majority of vCJD cases have occurred, fewer than 200 cases have been reported. CJD incidence peaked between 1999 and 2000 and has been declining since.

Regulating potential sources of vCJD

Most countries have taken steps to prevent BSE-infected tissue from entering the food supply, including:

  • Tight restrictions on importation of cattle from countries where BSE is common
  • Restrictions on animal feed
  • Strict procedures for dealing with sick animals
  • Surveillance and testing methods for tracking cattle health
  • Restrictions on which parts of cattle can be processed for food


Diagnosis

The diagnosis of CJD is suspected when there are typical clinical symptoms and signs such as rapidly progressing dementia with startle myoclonus. Further investigation can then be performed to support the diagnosis including

  • Electroencephalography— often has characteristic generalized periodic sharp wave pattern (~80% of pts by 6 months)
  • Cerebrospinal fluid analysis for 14-3-3 protein
  • MRI of the brain—often shows high signal intensity in the caudate nucleus and putamen bilaterally on T2-weighted images.
  • Research in 2010 and 2011 identified a possible blood test for CJD. The test attempts to identify the prion responsible for the disease. However, it has not yet been demonstrated if it is able to detect the prions in early stages of the disease.

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 been based mostly 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 seen primarily when combined with a test for the 14-3-3 protein. As of 2010, 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 2014 a human study showed a nasal brushing method that can accurately detect PrP in the olfactory epithelial of CJD patients. . This finding creates new opportunities for minimally invasive detection of 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 for all other forms of prion disease. 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.

However, 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.

Prognosis

Prognosis of Creutzfeldt-Jakob Disease: Poor. Typically death within 12 months. Prognosis for Creutzfeldt-Jakob Disease: About 90 percent of patients die within 1 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. (Source: excerpt from NINDS Creutzfeldt-Jakob Disease Information Page: NINDS) Duration of Creutzfeldt-Jakob Disease: In more than 85 percent of cases, the duration of CJD is less than 1 year (median: 4 months) after onset of symptoms. (Source: excerpt from Facts About Creutzfeldt-Jakob Disease: CDC-OC).

Treatment

As of 2015 , 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 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, clonazepam and benzodiazepine, to reduce muscle jerks.

Scientists from the 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 their clinical study. The efficacy of quinacrine was also assessed in a rigorous clinical trial in the UK and the results were published in Lancet Neurology, and concluded that quinacrine had no measurable effect on the clinical course of CJD.

In a 2013 paper published in the Proceedings of the National Academy of Sciences, scientists from The Scripps Research Institute reported that Astemizole, a medication approved for human use, has been found to have anti-prion activity and may lead to a treatment for Creutzfeldt–Jakob disease.