Complications (1)
- Alzheimer's: Managing sleep problems
Definition (1)
- Early-onset Alzheimer's: When symptoms begin before 65
Risk factors (2)
- Alzheimer's: Is it in your genes?
- Diabetes and Alzheimer's linked
Symptoms (3)
- Alzheimer's stages: How the disease progresses
- Memory loss: When to seek help
- Alzheimer's or depression: Could it be both?
Tests and diagnosis (3)
- Diagnosing Alzheimer's: An interview with a Mayo Clinic specialist
- SPECT scan
- Positron emission tomography (PET) scan
Treatments and drugs (3)
- Alzheimer's: Getting the most from medical appointments
- Alzheimer's drugs slow progression of disease
- Alzheimer's treatments: What's on the horizon?
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continued:
Alzheimer's: Is it in your genes?
Early-onset Alzheimer's
Less than 10 percent of the people who develop Alzheimer's disease have the early-onset variety, which typically begins before the age of 65.
Scientists have identified three genes that 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 (PS1)
- Presenilin 2 (PS2)
These abnormal genes cause the production of excessive amounts of a toxic protein fragment called amyloid-beta peptide. As these fragments proliferate in the brain, the brain cells start dying and the signs and symptoms of Alzheimer's begin.
However, at least half of the people who have early-onset Alzheimer's don't have any of these three gene mutations. That suggests that this aggressive 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.
While testing for the mutant genes that have been linked to early-onset Alzheimer's — APP, PS1 and PS2 — may provide more certain results, the emotional consequences of having that information might be devastating. And the information could result in employment or health insurance discrimination.
Even without genetic testing, doctors can diagnose Alzheimer's with 90 percent accuracy.
Researchers and genes
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, call 800-526-2839.
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