Creutzfeldt-Jakob Disease
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Related Key Words and Synonyms: CJD
Overview
This lesion is typical of many prion diseases. Classic CJD is a human prion disease.
Epidemiology and Demographics
Classic CJD has been recognized since the early 1920s. The most common form of classic CJD is believed to occur sporadically, caused by the spontaneous transformation of normal prion proteins into abnormal prions.
- This sporadic disease occurs worldwide, including the United States, at a rate of approximately one case per 1 million population per year, although rates of up to two cases per million are not unusual.
- The risk of CJD increases with age, and in persons aged over 50 years of age, the annual rate is approximately 3.4 cases per million.
- In recent years, the United States has reported fewer than 300 cases of CJD a year.
Whereas the majority of cases of CJD (about 85%) occur as sporadic disease, a smaller proportion of patients (5-15%) develop CJD because of inherited mutations of the prion protein gene. These inherited forms include Gerstmann-Straussler-Scheinker syndrome and fatal familial insomnia.
New concerns on incidence and prevalence
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 transmitted through cannibalism in Papua New Guinea when relatives would eat their dead relative's brains as a sign of mourning. In the 1950s, the practice was banned, thereby preventing any further possible transmission. 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 30 to 50 years.
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 BSE. This means that there may be many more vCJD patients who have longer incubation periods, which may surface many years later.
Pathophysiology & Etiology
Clinical and Pathologic Characteristics of Classic CJD
Classic CJD characteristics, as compared to variant CJD, are presented in the table below.
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, chronic wasting disease (CWD), and scrapie in sheep.
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 2006, its biological function is unknown. The other conformational state is very poorly water-soluble and readily forms protein aggregates.
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 prions in affected cells. This mass of misfolded proteins disrupts cell function and causes cell death. Once the prion is transmitted, the defective proteins invade the brain and are produced in a self-sustaining feedback loop, causing exponential spread of the prion, death within a few months, although a few patients have been known to live as long as two years.
Stanley B. Prusiner was awarded the Nobel Prize in physiology or medicine in 1997 for his discovery of prions. Yale University neuropathologist Laura Manuelidis has challenged this explanation for the disease. In January 2007 she and her colleagues published a study in the Proceedings of the National Academy of Science asserting that they have found a virus responsible for the diseases.
Transmission
The defective protein can be transmitted by human growth hormone (hGH) products, 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. 10 to 15% of CJD cases are inherited. (CDC)
The disease has also been shown to result from usage of HGH drawn from the pituitary glands of cadavers who died from Creutzfeldt-Jakob Disease, though the known incidence of this cause is (as of April 2004) quite small. The risk of infection through cadaveric HGH usage in the U.S. only 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, although there are fears — based on animal studies — that consuming beef or beef products containing prion particles can also cause the development of classic CJD. Cannibalism has also been implicated as a transmission mechanism for abnormal prions, causing the disease known as kuru, found primarily among women and children of the Fore tribe in Papua New Guinea. While the men of the tribe ate the body of the deceased and were not affected, the women and children ate the brain and contracted the disease from infected brain 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 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 dissolves protein at a molecular level.
Natural History
The disease was first described by two German neurologists, Hans Gerhard Creutzfeldt and Alfons Maria Jakob. Some of the clinical findings described in their first papers do not match current criteria for Creutzfeldt-Jakob disease, and it is considered highly likely that at least two of the patients in initial studies were suffering from a different disorder.
Diagnosis
The diagnosis of CJD is suspected when there are typical clinical symptoms and signs such as rapidly progressing dementia with myoclonus.
History and Symptoms
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 a typical diagnostic electroencephalogram tracing.
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. 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 'spongy' appearance of the brain tissue.
Laboratory Findings
Cerebrospinal fluid analysis for 14-3-3 protein
MRI and CT
MRI of the brain - often shows high signal intensity in the caudate nucleus and putamen bilaterally on T2-weighted images
Electroencephalography
Often has characteristic triphasic spikes.
Other Diagnostic Studies
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.
Treatment
As of December 2006, there is no cure for CJD, a fatal disease, and the search for viable treatments 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 seems to slow down the progression of the otherwise untreatable disease, and may have contributed to the longer than expected survival of the seven patients that were studied.
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.
References
- http://www.cdc.gov/ncidod/dvrd/cjd/
- http://en.wikipedia.org/wiki/Creutzfeldt-Jakob_disease#Transmission
Acknowledgements
The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.
Suggested Reading and Key General References
Suggested Links and Web Resources
For Patients
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
