Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.


Genetic and Rare Diseases Information Center (GARD)

Print friendly version

Alzheimer disease type 4

Other Names for this Disease
  • AD4
  • Alzheimer disease 4
  • Alzheimer disease familial type 4
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.


What is Alzheimer disease?

What is early-onset Alzheimer disease and how is it inherited?

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. Alzheimer disease currently affects about 5 million people.[1] About 75 percent of Alzheimer disease cases are classified as sporadic, which means they occur in people with no history of the disorder in their family. Although the cause of these cases is unknown, genetic changes are likely to play a role. Virtually all sporadic Alzheimer disease begins after age 65, and the risk of developing this condition increases as a person gets older.

The remaining cases of Alzheimer disease are familial, which means they are found in multiple members of a family. Familial Alzheimer disease can be divided into early-onset disease (symptoms begin before age 65) and late-onset disease (symptoms begin after age 65).[2]

Last updated: 7/2/2013

What is early-onset Alzheimer disease and how is it inherited?

Early-onset Alzheimer disease is a form of Alzheimer disease that begins to affect people before the age of 65. Fewer than 2% of families with Alzheimer disease have early-onset familial Alzheimer disease. Researchers have identified three genes that cause early-onset familial Alzheimer disease, the amyloid beta precursor protein (APP) gene, presenilin 1 (PSEN1) gene, and presenilin 2 (PSEN2) gene. In general, most individuals diagnosed as having early-onset Alzheimer disease have had an affected parent.

Early-onset Alzheimer disease is often inherited in an autosomal dominant manner, meaning that the risk to offspring of an individual with early-onset familial Alzheimer disease is 50% if a mutation is found in APP, PSEN1, or PSEN2. Occasionally, neither parent is affected, but a second-degree relative (e.g., an uncle, aunt and/or grandparent) has or had early-onset Alzheimer disease.

You can read a comprehensive review of early-onset Alzheimer disease on the GeneReviews Web site.
Last updated: 7/5/2013

  1. Alzheimer Disease. Genetics Home Reference. October 2006; Accessed 1/18/2008.
  2. Alzheimer's Facts and Figures. Alzheimer's association. October 16, 2007; Accessed 1/18/2008.