[Genes in Alzheimer's disease].
BACKGROUND
Alzheimer's disease (AD) is the most frequent degenerative dementia among the elderly population. Families that have an autosomal dominant pattern for AD constitute about 13% of early cases (< or = 65 years) and less than 0.01% of the total number of patients.


METHODS
Molecular analysis of families with early onset AD has made it possible to identify mutations in three different genes that are responsible for the disease: the gene encoding for the amyloid precursor protein peptide (APP), and the presenilin 1 (PSEN1) and presenilin 2 (PSEN2) genes. Yet, these genes are involved in less than 5% of the total number of cases of AD. The remaining AD patients are mostly cases of late or familial onset, where the disease appears as a result of a complex interaction among environmental factors and individual predisposing genetic traits. A large number of molecular genetics studies have clearly implicated the APOE epsilon4 allele as a proven risk factor for the late form of AD in almost all the populations that have been studied.


CONCLUSIONS
Although the APOE epsilon4 allele is the only proven genetic risk factor for the late form of the disease, genetic epidemiological studies suggest that other loci are also involved.
Servicio de Psiquiatría, Hospital Universitario 12 de Octubre, Madrid, Spain. jhoenicka.hdoc@salud.madrid.org
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D017668:Age of Onset; D000544:Alzheimer Disease / Q000235:genetics* / Q000503:physiopathology; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D053327:Apolipoprotein E4; D001057:Apolipoproteins E / Q000235:genetics; D002877:Chromosomes, Human; D020022:Genetic Predisposition to Disease; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D009154:Mutation; D053764:Presenilin-1; D053766:Presenilin-2; D012307:Risk Factors
D016564:Amyloid beta-Protein Precursor; D053327:Apolipoprotein E4; D001057:Apolipoproteins E; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C508861:PSEN2 protein, human; D053764:Presenilin-1; D053766:Presenilin-2