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Alzheimer disease

Alzheimer disease

What is Alzheimer disease?

Alzheimer disease is a degenerative disease of the brain that causes gradual loss of memory, judgment, and ability to function socially.

Genetic changes are related to the following types of Alzheimer disease.

Additional types of Alzheimer disease have been reported, but the responsible mutations have not been adequately described, or the cause is not genetic.

Memory loss is the most common sign of this disease. The loss of memory becomes more than the usual forgetfulness experienced by all older people. Even in familiar settings, a person with Alzheimer disease may get lost or become confused. Normal daily tasks, such as doing simple math and naming objects and people, become challenging. Preparing meals, doing laundry, and performing other household chores can also become difficult. Problems with dressing, eating, and personal care as well as agitation, restlessness, and inappropriate behavior develop as the disease progresses. In addition, personality changes and an inability to interact in a socially appropriate manner are common. The patient's speech eventually becomes difficult to understand, and the individual may require total care. The course of the disease is usually 8 to 10 years, but can range from 1 to 25 years.

How common is Alzheimer disease?

Alzheimer disease currently affects an estimated 4.5 million Americans. Because more people are living longer, this number is expected to triple in the next 20 years.

What genes are related to Alzheimer disease?

Mutations in the APP, PSEN1, and PSEN2 genes cause Alzheimer disease.

Variations of the APOE gene increase the risk of developing Alzheimer disease.

About 75 percent of Alzheimer disease cases are classified as sporadic, which means that no other blood relatives are affected. The cause of these cases is not known at this time, but genetics may play a part. The risk of developing the condition increases as a person gets older.

The remaining 25 percent of Alzheimer disease cases are hereditary, which means they are caused by mutated genes and tend to cluster in families. These cases can be divided into early-onset disease (symptoms begin before 65 years of age) and late-onset disease (symptoms begin after age 65).

Researchers have identified three genes that cause early-onset Alzheimer disease. The amyloid precursor protein (APP) gene, presenilin 1 (PSEN1) gene, and presenilin 2 (PSEN2) gene lead to Alzheimer disease types 1, 3, and 4, respectively.

The genetic causes of late-onset Alzheimer disease are less clear. No gene that definitely causes the condition has been identified. However, a gene called APOE has been studied extensively as a risk factor for the disease. In particular, one form (or allele) of this gene seems to increase an individual's risk for developing type 2 Alzheimer disease.

How do people inherit Alzheimer disease?

The early-onset forms of Alzheimer disease (types 1, 3, and 4) are inherited in an autosomal dominant pattern, which means only one copy of the altered gene is necessary to cause the disorder. In most cases, an affected person has one affected parent.

Where can I find information about Alzheimer disease?

You may find the following resources about Alzheimer disease helpful.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for Alzheimer disease?

  • AD
  • Alzheimer dementia (AD)
  • Alzheimer sclerosis
  • Alzheimer's Disease
  • Alzheimer syndrome
  • Alzheimer-type dementia (ATD)
  • DAT - Dementia Alzheimer's type
  • familial Alzheimer disease (FAD)
  • Presenile and senile dementia
  • Primary Senile Degenerative Dementia
  • SDAT

What if I still have specific questions about Alzheimer disease?

Where can I find general information about genetic conditions?

What glossary definitions help with understanding Alzheimer disease?

allele ; amyloid ; amyloid plaque ; autosomal ; autosomal dominant ; degenerative ; dementia ; familial ; gene ; mutation ; peptide ; protein ; sclerosis ; sign ; sporadic ; symptom

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

 
References (2 links)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.

 
Last Comprehensive Review: January 2004
Published: November 12, 2004

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