APOE-e4 is one of three common forms of the APOE gene; the others are APOE-e2 and APOE-e3. APOE provides the blueprint for one of the proteins that carries cholesterol in the bloodstream.
Everyone inherits a copy of some form of APOE from each parent. Those who inherit one copy of APOE-e4 have an increased risk of developing Alzheimer’s. Those who inherit two copies have an even higher risk, but not a certainty. Scientists do not yet know how APOE-e4 raises risk. In addition to raising risk, APOE-e4 may tend to make symptoms appear at a younger age than usual.
Experts believe there may be as many as a dozen other Alzheimer risk genes in addition to APOE-e4.
2) Deterministic genes directly cause a disease, guaranteeing that anyone who inherits them will develop the disorder. Scientists have found rare genes that directly cause Alzheimer’s in only a few hundred extended families worldwide.
When Alzheimer’s disease is caused by deterministic genes, it is called “familial Alzheimer’s disease,” and many family members in multiple generations are affected. True familial Alzheimer’s accounts for less than 5 percent of cases.
Genetic tests are available for both APOE-e4 and the rare genes that directly cause Alzheimer’s. However, health professionals do not currently recommend routine genetic testing for Alzheimer’s disease. Testing for APOE-e4 is sometimes included as a part of research studies.
Died of Alzheimer's October 14, 2006