Alzheimer's disease. Clinical molecular genetics.

The study of the genetics of AD has shown that at least three loci are involved in causing the disease: (1) the APP gene, in which a series of mutations cause the disease to develop in 50- to 60-year-old patients; (2) the ApoE gene in which genetic variability (the E4 allele) is a predisposing factor for the development of late-onset disease; and (3) an as-yet-unidentified chromosome 14 locus that causes the onset of AD before 50 years of age. These genetic findings point to a single process: fibrillar beta-amyloid deposition as central to the pathogenesis of the disease. These genetic findings are already being used as an aid to the diagnosis of AD, and it is likely that their use in this regard will increase. The need for the genetic education of primary care physicians and the general public is of great importance so that informed debate about appropriate use of genetic data for diagnosis of AD can take place.