Most dementia is not inherited. There are some hereditary conditions that are associated with dementia the foremost being Alzheimer disease.
Dementia is a general term that describes a group of symptoms-such as loss of memory, judgment, language, complex motor skills, and other intellectual function-caused by the permanent damage or death of the brain's nerve cells, or neurons. One or more of several diseases, including Alzheimer disease (AD), can cause dementia. AD is the most common cause of dementia in persons over the age of 65 and represents about 60 percent of all dementias. There are two types of the disease: sporadic Alzheimer's disease and familial Alzheimer disease (FAD). Unlike sporadic Alzheimer's disease, FAD follows an obvious inheritance pattern. Less than ten percent of Alzheimer's disease cases are FAD. This rare form of Alzheimer's disease usually occurs between the ages of 30 and 60. Familial AD is broken down into two categories depending upon the age of onset of AD in an individual: late-onset AD and early-onset AD.
Late-Onset Familial Alzheimer Disease
Families with late-onset AD typically have one or more affected relatives, most or all of whom have onset of dementia after the age of 65 years. Although some susceptibility genes have been identified, genetic testing is not appropriate for the majority of late-onset AD families.
Early-Onset Familial Alzheimer Disease
Families with early-onset AD typically have several affected biological on the same side of the family who have onset of dementia before the age of 65, typically in the forties. Early-onset AD is rare and accounts for about 1-5% of all AD. Mutations in 3 genes have been identified in families with early-onset AD; these genes are the presenilin-1 gene (PSEN1), presenilin-2 gene (PSEN2), and the amyloid precursor protein gene (APP). Individuals with a family history of early-onset familial AD may have a 50% chance of developing AD and genetic testing is available for the PSEN1 and PSEN2 genes.
Is there a genetic test for Familial Alzheimer’s disease?
Genetic testing is available for Early-Onset Familial Alzheimer Disease
The family history, ages at diagnosis and neurological features in a family are used to determine the likelihood of Early-Onset Familial Alzheimer Disease and, if this condition is suspected, which gene(s) should be analyzed.
It is generally most informative if a relative who has had symptoms related to Alzheimer’s disease is tested first, to determine if an identifiable gene mutation exists in the family. If a mutation is identified in an affected relative, at-risk family members may elect to be tested for the familial mutation; those testing positive have a significantly increased risk of developing Alzheimer’s disease, while those relatives testing negative may be told that they have the general population risk. Unfortunately, there are currently no effective treatments or cures.
What should I do now?
Please use this section as background education. It is not a substitute for a clinical visit to our Center or discussion of a possible hereditary condition with your physician.
Make an appointment with your physician to discuss your risk of hereditary dementia or familial Alzheimer disease.
Make an appointment with the Center for Medical Genetics by calling 847.570.1029.
E-mail this page to a friend or loved one that may be at risk.