Alzheimer Disease, Genetics of

n almost 20 years of ongoing research, the genetic cause of Alzheimer disease (AD) is understood for less than 5% of all cases. For the remainder of AD sufferers, multiple genetic and environmental factors probably play a role in contributing to disease onset, severity and progression. To date, only the gene encoding apolipoprotein E (APOE) is recognized as a major genetic risk factor, but numerous other candidates have emerged. What we have learned from these findings is discussed as are the results from recent genome linkage studies on affected sibling pairs which have yielded new chromosomal regions of interest and in turn new candidate genes alongside those reported from ongoing candidate gene association studies.