Prion disease


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Related to Prion disease: Creutzfeldt-Jakob disease

Prion disease

Transmissible spongiform encephalopathies in both humans and animals. Scrapie is the most common form in animals, while in humans the most prevalent form is Creutzfeldt-Jakob disease. This group of disorders is characterized at a neuropathological level by vacuolation of the brain's gray matter (spongiform change). They were initially considered to be examples of slow virus infections. Experimental work has consistently failed to demonstrate detectable nucleic acids—both ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)—as constituting part of the infectious agent. Contemporary understanding suggests that the infectious particles are composed predominantly, or perhaps even solely, of protein, and from this concept was derived the acronym prion (proteinaceous infectious particles). Also of interest is the apparent paradox of how these disorders can be simultaneously infectious and yet inherited in an autosomal dominant fashion (from a gene on a chromosome other than a sex chromosome).

Disorders

Scrapie, which occurs naturally in sheep and goats, was the first of the spongiform encephalopathies to be described. An increasing range of animal species have been recognized as occasional natural hosts of this type of disease. Bovine spongioform encephalopathy, commonly known as mad cow disease, has been epidemic in British cattle. The first confirmed cases were reported in late 1986. By early 1995 it had been identified in almost 150,000 cattle and more than half of all British herds. Its exact origin is not known, but claims that it came from sheep are now discredited.

So far, animal models have indicated that only central nervous system tissue has been shown to transmit the disease after oral ingestion—a diverse range of other organs, including udder, skeletal muscle, lymph nodes, liver, and buffy coat of blood (white blood cells) proving noninfectious.

The currently recognized spectrum of human disorders encompasses kuru, Creutzfeldt-Jakob disease, Gerstmann-Straussler-Scheinker disease, and fatal familial insomnia. All, including familial cases, have been shown to be transmissible to animals and hence potentially infectious; all are invariably fatal with no effective treatments currently available.

Human-to-human transmission

A variety of mechanisms of human-to-human transmission have been described. Transmission is due in part to the ineffectiveness of conventional sterilization and disinfection procedures to control the infectivity of transmissible spongiform encephalopathies. Numerically, pituitary hormone–related Creutzfeldt-Jakob disease is the most important form of human-to-human transmission of disease. However, epidemiological evidence suggests that there is no increased risk of contracting Creutzfeldt-Jakob disease from exposure in the form of close personal contact during domestic and occupational activities. Incubation periods in cases involving human-to-human transmission appear to vary enormously, depending upon the mechanism of inoculation. Current evidence suggests that transmission of Creutzfeldt-Jakob disease from mother to child does not occur. Two important factors pertaining to transmissibility are the method of inoculation and the dose of infectious material administered. A high dose of infectious material administered by direct intracerebral inoculation is clearly the most effective method of transmissibility and generally provides the shortest incubation time. See Brain, Mutation, Nervous system disorders

References in periodicals archive ?
Experts say this marks a significant milestone in quest to better understand prion diseases in people, and could eventually aid the development of new therapies.
However, we did not detect clinical prion disease, supporting a slower rate of vCJD conversion compared with that among Tg[Met.
The couple worked with Harvard University geneticist Daniel MacArthur to examine genetic data from 16,025 people with prion diseases and 60,706 others who had the protein-coding parts of their genomes sequenced as part of the ExAC project, an effort to find disease-causing genetic variants (SN: 12/12/15, p.
In contrast with virus infection transitory symptoms, chronic neurodegeneration of prion disease inflicts permanent symptoms that aggravate as disease progresses.
Infectious Disease Section, Internal Medicine Department, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico; ([dagger]) National Prion Disease Pathology Surveillance Center (NPDPSC), Case Western Reserve University, School of Medicine, Cleveland, OH; ([double dagger]) PhD Program in Experimental Physiopathology and Neuroscience --Second University of Naples, Italy; ([section]) Neurology Department, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico; ** Division of Neurology, Department of Clinical and Experimental Medicine, Second University of Naples, Italy; ([dagger][dagger]) Neurology Section, HIMA Hospital, Caguas, Puerto Rico
First described in 1936, Gerstmann-Straussler-Scheinkerr (GSS) syndrome is a familial human prion disease caused by the archetypal mutation P102L of the Prnp gene.
A recent study demonstrated that 32% of patients referred to the National Prion Disease Pathology Surveillance Center for autopsy because of suspected CJD were actually found to have other diagnoses.
Mallucci's team found that the buildup of mis-folded proteins in the brains of mice with prion disease activated a natural defense mechanism in cells, which switches off the production of new proteins.
Of all the prion diseases, a better diagnostic test is needed for sporadic CJD, which accounts for about 85% of all human prion diseases, but there is no evidence that sporadic CJD is in the blood, Dr.
Since 1996, in Japan, a nongovernmental CJD surveillance group supported by the Ministry of Health and Welfare (later renamed the Ministry of Health, Labour, and Welfare) has conducted a national survey seeking cases of human prion disease.
The foundations have been laid for recruitment of a national cohort of at least 1,000 ranchers and farmers across Canada who are willing to participate in a longitudinal study on the impact of prion disease.
The disease was misdiagnosed until the early 1990s, when it was finally recognized to be fatal familial insomnia (FFI), a rare genetic form of a prion disease with no known cure.