Is Alzheimer Disease genetic?
Often, there is not a single genetic cause that we can identify. Genes seem to play a role in why a person has Alzheimer disease, but we are not always able to find a genetic cause. Around 25% of cases seem to be due to familial Alzheimer disease. These families have multiple people diagnosed with Alzheimer disease.
The other 75% of the time, Alzheimer disease does not appear to be the familial form. It is in the sporadic form. Sporadic means it is the first case of Alzheimer disease in a family. The cause of sporadic Alzheimer disease is not well understood. Sporadic Alzheimer Disease is likely caused by a combination of genetic and environmental factors.
In rare cases, there is a strong family history of early onset Alzheimer disease. In the early onset form, people are diagnosed with Alzheimer disease before the age of 65. There are three known genes that cause the early onset familial form of Alzheimer disease. The genes are PSEN1, APP, and PSEN2 and genetic testing is available.