[Etiology of Alzheimer's disease].

The major factor that causes problems in studies on the aetiology of Alzheimer's disease (AD) is the clinical heterogeneity of the condition. Familial early-onset AD and familial late-onset AD are differentiated from sporadic AD. Aetiologically a genetic defect on chromosome 21 is the most important factor, at least in some cases of AD. In familial AD and autosomal dominant inheritance with complete penetrance in old age is thought to be possible. In sporadic AD the role of genetic and exogenous factors (infectious agents, aluminium) is unknown. The current status of knowledge about the aetiology of Alzheimer's disease is reviewed with reference to the literature.