All people with Down syndrome develop Alzheimer’s disease. Adults with Down syndrome often are in their mid to late 40s or early 50s when symptoms might first appear.
The symptoms of Alzheimer’s disease might be expressed differently among adults with Down syndrome. For example, in the early stages of the disease, memory loss is not always prominent. In addition, not all symptoms ordinarily associated with Alzheimer’s disease will occur. Generally, changes in activities of daily living skills occur, and the person with Down syndrome might begin to have seizures when he or she had not had them in the past. Changes in mental processes—such as thinking, reasoning, and judgment—also might be present, but they often are not readily noticeable because of limitation of the individual’s functioning in general.
Why do people with Down syndrome get Alzheimer’s disease?
Current research shows that the extra "gene dosage" caused by the abnormal third chromosome of Down syndrome might be a factor in the development of Alzheimer’s disease. Interest also is being focused on the early onset of Alzheimer’s disease in individuals with Down syndrome, which might be related to the early aging of the Down syndrome brain.
Down syndrome occurs because a gene error results in three copies instead of 2 of chromosome 21. This chromosome has the gene for the This chromosome has the gene for the protein that causes the disease. The extra "gene dose" causes too much protein to be produced.
Lott, I.; Head, E. Alzheimer disease and Down syndrome: factors in pathogenesis. Neurobiology of Aging. Mar 2005; vol. 26(3), pp. 383-389.
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