Is Alzheimer's Hereditary?
Alzheimer's disease is a form of dementia that is caused by protein misfolding. Some forms of it are hereditary, though in other cases it is not understood what initiates the disease.
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History
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Alzheimer's disease, an incurable and progressive type of dementia, generally affects those age 65 and older, though there are cases that begin earlier. One of the earliest symptoms is memory loss, which gradually progresses to more advanced confusion, restlessness, problems with language, and hallucinations. Alzheimer's disease is ultimately fatal as basic bodily systems eventually shut down.
Theories/Speculation
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Alzheimer's disease is thought to be related to the beta-amyloid protein, which exists in two forms: a shorter, more common form, and a longer form which appears to misfold easily. Misfolded beta-amyloid gradually accumulates and forms larger structures, called fibrils, which are thought to cause the death of brain cells. The beta-amyloid protein is a smaller part of a larger complex, called the amyloid precursor protein.
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Types
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There are a few genetic mutations that can be passed along that carry a heightened risk to Alzheimer's. One heritable form of the disease involves mutations within the beta-amyloid protein itself. These mutations can increase the tendency of the protein to misfold, heightening the risk for contracting the disease and causing it to start earlier.
Features
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Another genetic mutation involves proteins that break down the amyloid precursor protein. The beta-amyloid protein has two forms, and which of these forms that is produced depends on proteins called the presenilins. These proteins can cause more of the longer, more dangerous form of the beta-amyloid protein to be produced, increasing the risk of the disease.
Expert Insight
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One of the strongest genetic factors for Alzheimer's disease is the presence of a specific version of the apolipoprotein E gene. This protein is important for fat metabolism and while it is strongly linked with an increased risk of Alzheimer's disease, there are no explanations as to why there is such a strong link. This gene is present in approximately 50% of Alzheimer's disease patients and is heritable.
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