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Types of Alzheimer's Disease

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    There are three known types of Alzheimer’s disease. They include:

    • Early-onset Alzheimer's. This is a rare form of Alzheimer's disease in which people are diagnosed with the disease before age 65. Less than 10% of all Alzheimer's disease patients have this type. Because they experience premature aging, people with Down syndrome are particularly at risk for a form of early onset Alzheimer's disease. Adults with Down syndrome are often in their mid- to late 40s or early 50s when symptoms first appear.

      Younger people who develop Alzheimer's disease have more of the brain abnormalities that are associated with it. Early-onset Alzheimer's appears to be linked with a genetic defect on chromosome 14, to which late-onset Alzheimer's is not linked. A condition called myoclonus -- a form of muscle twitching and spasm -- is also more commonly seen in early-onset Alzheimer's than in late-onset Alzheimer's.

    • Late-onset Alzheimer's. This is the most common form of Alzheimer's disease, accounting for about 90% of cases, and usually occurs after age 65. Late-onset Alzheimer's disease strikes almost half of all people over the age of 85 and may or may not be hereditary. Late-onset dementia is also called sporadic Alzheimer's disease.

    • Familial Alzheimer's disease (FAD). This is a form of Alzheimer's disease that is known to be entirely inherited. In affected families, members of at least two generations have had Alzheimer's disease. FAD is extremely rare, accounting for less than 1% of all cases of Alzheimer's disease. It has a much earlier onset (often in the 40s).

     

    Recommended Related to Alzheimer's

    Understanding Alzheimer's Disease -- Symptoms

    The symptoms of Alzheimer's disease often come on gradually. They then typically progress over several years to the point of causing major impairment. Alzheimer's can be divided into mild, moderate, or severe stages. Each stage has a separate set of symptoms. But symptoms can vary from person to person. And the length of each stage can also vary.

    Read the Understanding Alzheimer's Disease -- Symptoms article > >

     

    WebMD Medical Reference

    Reviewed by Neil Lava, MD on July 10, 2014
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