Complications (1)
- Alzheimer's: Managing sleep problems
Coping and support (3)
- Caregiving: Tips for long-distance caregivers
- Caregiver stress: Tips for taking care of yourself
- Alzheimer's: Planning for the holidays
Definition (1)
- Early-onset Alzheimer's: When symptoms begin before 65
Prevention (1)
- Home safety tips: Preparing for Alzheimer's caregiving
Risk factors (2)
- Diabetes and Alzheimer's linked
- Alzheimer's genes: Are you at risk?
Symptoms (3)
- Memory loss: When to seek help
- Alzheimer's stages: How the disease progresses
- Alzheimer's or depression: Could it be both?
Tests and diagnosis (4)
- Diagnosing Alzheimer's: An interview with a Mayo Clinic specialist
- Sharing Alzheimer's diagnosis: Tips for caregivers
- Positron emission tomography (PET) scan
- see all in Tests and diagnosis
Treatments and drugs (3)
- Alzheimer's: 7 tips for medical visits
- Alzheimer's: Drugs help manage symptoms
- Alzheimer's treatments: What's on the horizon?
About our e-newsletters
- Free e-newsletters
- Mayo Clinic expertise
- We do not share your e-mail address
Housecall, our weekly general-interest e-newsletter, keeps you up to date on a wide variety of health topics with timely, reliable, practical information, recipes, blogs, questions and answers with Mayo Clinic experts and more. Our biweekly topic-specific e-newsletters also include blogs, questions and answers with Mayo Clinic experts, and other useful information that will help you manage your health.
Housecall Archives
Mayo Clinic Housecall
Stay up to date on the latest health information.
What you get
- Free weekly e-newsletter
- Mayo Clinic expertise
- Recipes, tools and other helpful information
- We do not share your e-mail address
continued:
Alzheimer's genes: Are you at risk?
Early-onset Alzheimer's
A very small percentage of the people who develop Alzheimer's disease have the early-onset variety, which is classified as beginning before the age of 65.
Scientists have identified three genes in which mutations cause early-onset Alzheimer's. If you inherit one of these mutated genes from either parent, you almost certainly will experience Alzheimer's symptoms before the age of 65. The genes involved are:
- Amyloid precursor protein (APP)
- Presenilin 1 (PSEN1)
- Presenilin 2 (PSEN2)
Mutations of these genes cause the production of excessive amounts of a toxic protein fragment called amyloid-beta peptide. As these fragments stick together and deposit in the brain as amyloid plaques — and somehow induce changes in another brain protein called tau — the brain cells start dying and the signs and symptoms of Alzheimer's begin.
However, some people who have early-onset Alzheimer's don't have mutations in any of these three genes. That suggests that this early onset form of Alzheimer's disease is linked to other genetic mutations that haven't been identified yet.
Genetic testing
Most experts don't recommend genetic testing for late-onset Alzheimer's. In some instances of early-onset Alzheimer's, however, genetic testing may be appropriate.
In the case of APOE, knowing whether you have the e4 variety really doesn't tell you much. Although many people with APOE e4 develop Alzheimer's, many don't. Conversely, some people with no APOE e4 genes get Alzheimer's. Most clinicians discourage testing for the APOE genotype, as the results are often difficult to interpret.
Testing for the mutant genes that have been linked to early-onset Alzheimer's — APP, PSEN1 and PSEN2 — may provide more certain results and have implications for current and future therapeutic drug trials. But it's also important to weigh the emotional consequences of having that information. There also may be eligibility implications for certain forms of insurance, such as disability, long term care and life insurance.
Even without genetic testing, doctors can diagnose Alzheimer's with 90 percent accuracy.
Researchers and genes
Researchers suspect that there are dozens more genes that affect Alzheimer's disease risk that have not yet been identified or confirmed. Scientists study the genetics of Alzheimer's disease because understanding the basis of a disease may provide clues about how to combat it. Such information may prove vital in the development of new ways to treat, or even prevent, Alzheimer's disease in the future.
The Alzheimer's Disease Genetics Study, sponsored by the National Institute on Aging, is examining genetic information from families that have at least two siblings who have developed Alzheimer's after the age of 60. If your family is interested in participating in this study, visit the web site for the National Cell Repository for Alzheimer's Disease (NCRAD).
Previous page(2 of 2)
- Alzheimer's disease genetics fact sheet. National Institute on Aging. http://www.nia.nih.gov/alzheimers/publications/geneticsfs.htm. Accessed May 19, 2010.
- Genetic conditions: Alzheimer disease. Genetics Home Reference. http://ghr.nlm.nih.gov/condition/alzheimer-disease. Accessed May 19, 2010.
- Genes: APOE. Genetics Home Reference. http://ghr.nlm.nih.gov/gene/APOE. http://ghr.nlm.nih.gov/gene/APOE. Accessed May 19, 2010.
- Ertekin-Taner N. Genetics of Alzheimer's disease: A centennial review. Neurological Clinics. 2007;25:611.
- Meng Y, et al. Association between SORL1 and Alzheimer's disease in a genome-wide study. Neuroreport. 2007;18:1761.
- Sleegers K, et al. The pursuit of susceptibility genes for Alzheimer's disease: Progress and prospects. Trends in Genetics. 2010;26:84.
- Harold D, et al. Genome-wide association study identifies variants at CLU and PICALM associated with Alzheimer's disease. Nature Genetics. 2009;41:1088.
- Lambert JC, et al. Genome-wide association study identifies variants at CLU and CR1 associated with Alzheimer's disease. Nature Genetics. 2009;41:1094.
- Genetic testing. Alzheimer's Association. http://www.alz.org/national/documents/topicsheet_genetictesting.pdf. Accessed May 28, 2010.
- Genetic Information Nondiscrimination Act of 2008: Fact sheet. National Human Genome Research Institute. http://www.genome.gov/10002328. Accessed May 28, 2010.
Find Mayo Clinic on