This report describes general characteristics of the group of diseases classified as Alzheimer disease (AD). Alzheimer disease is a genetically heterogeneous disorder with multiple implicated genes and many loci that appear to confer susceptibility to the disease. A phenotypic series for subtypes of Alzheimer disease has not been defined by OMIM as of this update; see MIM:104300.
[updated Apr. 2017 by FlyBase; FBrf0222196]
Memory loss is the most common sign of Alzheimer disease. As the disorder progresses, some people with AD experience personality and behavioral changes; other common symptoms include agitation, restlessness, withdrawal, and loss of language skills. Total care is usually required during the advanced stages of the disease. Affected individuals usually survive 8 to 10 years after the appearance of symptoms, but the course of the disease can range from 1 to 25 years. Death usually results from pneumonia, malnutrition, or general body wasting. [from Genetics Home Reference, Alzheimer disease; 2016.01.08]
Alzheimer disease can be classified as early-onset or late-onset. The signs and symptoms of the early-onset form appear before age 65, while the late-onset form appears after age 65. The early-onset form is much less common than the late-onset form, accounting for less than 5 percent of all cases of Alzheimer disease. [from Genetics Home Reference, Alzheimer disease; 2016.01.08]
Alzheimer disease (AD) is the most common form of progressive dementia in the elderly. [from MIM:104300; 2016.01.08]
Early-onset familial Alzheimer disease (EOFAD) has been correlated with mutations in the APP gene (AD1, 10-15% of cases of EOFAD), the PSEN1 gene (AD3, 30-70% of cases of EOFAD) and the PSEN2 gene (AD4, <5% of cases of EOFAD). [from Gene Reviews, Early-Onset Familial Alzheimer Disease; 2016.01.08]
Alzheimer disease is a genetically heterogeneous disorder typically inherited as an autosomal dominant. In addition to several genes clearly implicated in familial AD, many candidate and susceptibility loci have been identified; mitochondrial gene variants may also be risk factors in AD. [from MIM:104300; 2016.01.08]
AD is characterized by the neuropathologic findings of intracellular neurofibrillary tangles and extracellular amyloid plaques that accumulate in vulnerable brain regions (Sennvik et al., 2000; pubmed:10653020). [from MIM:104300; 2016.01.08]
