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Alzheimer's Disease - Genetic Testing And Alzheimer's Disease

age aging social clinical individual dementia mutation risk

DNA testing can be performed to determine whether an individual has a mutation in one of the causative genes and/or whether he or she carries one or two copies of the APOEε4 susceptibility gene. Whether to test and which test to perform will depend on three conditions: family history of dementia, age of onset of disease, and clinical status of the individual. If a person has dementia, the test result could be useful in determining that the cause of the dementia is a form of AD. If a person has no symptoms of dementia, an estimate of the individual's risk could be developed, using the test. In the case of such estimates, both the actual accuracy of the test and the tested individual's understanding of its accuracy are of concern. While the consensus is that presymptomatic testing for causative mutations may be performed with appropriate counseling, debate over the safety and utility of APOE testing for individuals who do not show symptoms of Alzheimer's is ongoing.

In 2001, there was no treatment that prevented, much less cured, AD. Information regarding the risk of developing AD is useful only in life planning activities (such as purchasing or offering health insurance coverage or long-term care insurance coverage, or choosing retirement age) or in family planning. An individual's ability to cope with either an increased or a decreased risk may vary. Misuse of the information resulting in insurance or employment discrimination is possible. Absence of a causative gene mutation or of an APOEε4 susceptibility gene in either symptomatic or presymptomatic disease does not preclude AD as the cause of dementia or mean that the individual has no risk of developing AD in later years.

P. C. Gaskell Jr.

Bibliography

Mace, Nancy L., and Peter V. Rabins, eds. The 36-Hour Day, 3rd ed. Baltimore: The Johns Hopkins University Press, 1999.

St. George-Hyslop, Peter H. "Piecing Together Alzheimer's." Scientific American (Dec. 2000): 76-83.

Terry, Robert D., et al., eds. Alzheimer Disease, 3rd ed. Philadelphia, PA: Lippincott, Williams & Wilkins, 1999.

Internet Resources

"Ethical, Legal, and Social Issues." Human Genome Project, U.S. Department of Energy Office of Science. <http://www.ornl.gov/TechResources/Human_Genome/home.html>.

"Progress Report on Alzheimer's Disease, 1999." National Institute on Aging. Bethesda: National Institutes of Health, 1999. <http://www.nih.gov/nia/>.

The first preimplantation testing for the APP mutation was announced in February 2002. Four gene-negative embryos from a gene-positive woman were selected and implanted, and she gave birth to one child who was free of the gene mutation, which causes early-onset Alzheimer's disease.

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