Transmissible spongiform encephalopathy causes
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rinky Agnes Botleroo, M.B.B.S.
Overview
Prion diseases cause a progressive decline in brain function due to misfolding of proteins in the brain, called prion proteins (PrP) These are unique diseases,their aetiology may be genetic, sporadic or infectious via ingestion of infected foodstuffs and via iatrogenic means (e.g. blood transfusion/donated organs)
Causes
- About 10 -15 percent of all cases of prion disease are caused by mutations in the PRNP gene.
- These form prion diseases are classified as familial prion diseases as they can run in families.These are familial Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), and fatal familial insomnia (FFI)..The PRNP gene provides instructions for making a protein called prion protein (PrP).The precise function of this protein is unknown, researchers have proposed roles in several important processes. These include the transport of copper into cells, protection of brain cells (neurons) from injury (neuroprotection), and communication between neurons.In familial forms of prion disease, PRNP gene mutations result in the production of an abnormally shaped protein, known as PrPSc, from one copy of the gene. PrPSc can attach (bind) to the normal protein (PrPC) and promote its transformation into PrPSc,this process is not fully understood. The abnormal protein builds up in the brain, forming clumps which damage or destroy neurons. The loss of these cells creates microscopic sponge-like holes (vacuoles) in the brain, which leads to the signs and symptoms of prion disease.[1]
- Rest of the 85-90 percent of cases of prion disease are either sporadic or acquired.[1]
- People with sporadic prion disease have no family history of the disease and no identified mutation in the PRNP gene. Sporadic disease occurs when PrPC spontaneously, and for unknown reasons, is transformed into PrPSc. Sporadic forms of prion disease include sporadic Creutzfeldt-Jakob disease (sCJD), sporadic fatal insomnia (sFI), and variably protease-sensitive prionopathy (VPSPr).
- Acquired prion disease results from exposure to PrPSc from an outside source. For example, variant Creutzfeldt-Jakob disease (vCJD) is a type of acquired prion disease in humans that results from eating beef products containing PrPSc from cattle with prion disease. This form of the disease in cows is known as bovine spongiform encephalopathy (BSE) or, more commonly, "mad cow disease." Another example of an acquired human prion disease is kuru, which was identified in population in Papua New Guinea. The disorder was transmitted when individuals ate affected human tissue during cannibalistic funeral rituals.
- Prion diseases can rarely be caused by accidental exposure to PrPSc-contaminated tissues during a medical procedure. These 1-2 percent of prion diseases are classified as iatrogenic.[1]
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