What causes Alzheimer Disease?

Updated: Dec 23, 2019
  • Author: Thomas J Montine, MD, PhD; Chief Editor: Adekunle M Adesina, MD, PhD  more...
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Answer

Answer

Alzheimer disease (AD) is the most common neurodegenerative disease responsible for dementia. About half of dementia cases result from AD [3, 4] ; however, a variable but measurable amount of AD pathologic changes exist in most cognitively intact elderly individuals who undergo autopsy, indicating that AD is a chronic disease with latent and prodromal stages and suggesting that individuals may have varying abilities to compensate, either biologically or functionally, for the presence of AD. [8]

As with many neurodegenerative diseases, both rare autosomal-dominant forms of AD and more common sporadic forms with genetic risk factors without causative mutations exist. Abnormalities in three genes are known to cause AD with high penetrance: APP, PSEN1, and PSEN2. Autosomal-dominant forms of AD tend to be more severe and occur at a younger age than sporadic AD, but these are relatively rare. Sporadic AD accounts for the vast majority of AD cases. The neuropathologic changes of autosomal-dominant and sporadic AD are largely the same.


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