title: [Etiology and genetics of Alzheimer disease].
abstract: BACKGROUND
  Alzheimer's disease (AD) constitutes more than 50% of all dementias. The diagnosis is mainly based on clinical criteria and a definitive diagnosis of AD is made post-mortem with identification of amyloid plaques and neurofibrillary tangles. A small proportion of the patients are under the age of 60 at diagnosis, known as early-onset AD, and most of these cases have an evident genetic component. Aging is the most important risk factor for developing late-onset AD, but also genetic polymorphisms and many environmental conditions play a part in the development of this multifactorial disease.
  
  
  METHODS
  The Medline database was searched for "Alzheimer's and genetics". Histologic data were kindly provided from our hospital's department of pathology.
  
  
  CONCLUSIONS
  We consider most of the proved etiological factors, especially the three genetic loci which have been shown to be associated with early-onset AD: amyloid precursor protein (APP) gene, presenilin (PS)-1 and PS-2 genes. Mutations in the PS-1 gene at chromosome 14 are by far the most frequent genetic cause of AD. However, the large number of mutations makes genetic screening difficult. We also discuss the impact of the different ApoE alleles in developing late-onset AD, in addition to other mutations and polymorphisms.
authors.affiliation: Nevrologisk avdeling Haukeland Sykehus 5021 Bergen. anja.myhre@student.uib.no
authors.forename: Anja
authors.initials: A
authors.lastname: Myhre
authors.forename: Ole-Bjørn
authors.initials: OB
authors.lastname: Tysnes
mesh_terms: D000368:Aged; D000375:Aging; D000544:Alzheimer Disease / Q000209:etiology* / Q000235:genetics* / Q000473:pathology; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D001057:Apolipoproteins E / Q000235:genetics; D015897:Comorbidity; D005260:Female; D006801:Humans; D007375:Interleukin-1 / Q000235:genetics; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D008875:Middle Aged; D009154:Mutation; D053764:Presenilin-1; D053766:Presenilin-2; D012307:Risk Factors; D012959:Socioeconomic Factors; D016875:tau Proteins / Q000235:genetics
chemical_list: D016564:Amyloid beta-Protein Precursor; D001057:Apolipoproteins E; D007375:Interleukin-1; D008565:Membrane Proteins; C508853:PSEN1 protein, human; C508861:PSEN2 protein, human; D053764:Presenilin-1; D053766:Presenilin-2; D016875:tau Proteins