Early-onset Alzheimer’s disease, also called younger onset Alzheimer’s disease, is an uncommon form of dementia which affects individuals younger than the age of 65. Of all the people afflicted with Alzheimer’s disease, only an estimated five percent will develop symptoms at a younger age.
In limited cases, about a few hundred families worldwide, scientists have discovered several rare genes which directly cause this condition. Those who inherit these particular genes develop symptoms in their 30s, 40s and 50s. (1)
Autosomal Dominant Inheritance
In genetic research, familial Alzheimer’s is distinguished from sporadic Alzheimer’s. Currently, all cases of familial Alzheimer’s have an early onset. An estimated 50 percent of these cases are known to be caused by mutations in three genes located on three different chromosomes, which are the structures inside cells that house the genetic code.
Defects in the gene called amyloid precursor protein causes an abnormal form of the amyloid protein to be produced. Mutations in the gene called presenilin 1 cause an abnormal form of the presenilin 1 protein to be produced while mutations in the gene called presenilin 2 cause an abnormal form of the presenilin 2 protein to be produced.
The Fisher Center for Alzheimer’s Research Development states that “even if one of these
mutations is present in only one of the two copies of a gene inherited from a person’s parents, the person will inevitably develop that form of early-onset Alzheimer’s.”
This pattern of inheritance of a condition requiring only a single copy of a disease associated mutation is called autosomal dominant inheritance. (2)
Ten Warning Signs
Typically, the disease develops slowly and progressively worsens. Ten warning signs begin with memory loss, especially short term memory or forgetting recently learned information. Others become challenged by following a recipe, keeping track of monthly bills, concentrating or developing and following a plan.
Some find it hard to complete familiar tasks at home or at work, have trouble driving to a familiar location or remembering the rules of a favorite game. Confusion with time and place, such as losing track of dates or forgetting where you are, is a fourth warning sign.
Others have trouble understanding visual images, difficulty reading and judging distance. A person calls objects by the wrong name, struggles with vocabulary or stops in the middle of a conversation and has no idea how to continue.
Misplacing things and losing the ability to retrace steps is the seventh warning sign. Decreased or poor judgment, especially in dealing with money, signals the onset of Alzheimer’s. Withdrawal from social activities, hobbies and work projects plus changes in mood and behavior are among the ten warning signs.
Individuals without symptoms but who have a family member with the disease may want to pursue genetic testing. The experts at Genetic Health point out that
“clinical genetic testing is currently only available for one of the three known genes- PS1 ( presenilin 1). Testing for the other two genes is available on a research basis only.”
Testing is appropriate for people with a family member having early-onset Alzheimer’s disease. It may also be used to confirm a diagnosis in people with symptoms. It is important to test the right family member.
Genetic testing should begin with the family member who is most likely to have a mutation. Generally, that is the person who has already been diagnosed with the disease. If a PS1 mutation is found, other family members will be screened for this same mutation. (4)
Early onset Alzheimer’s disease poses unique challenges. It strikes individuals who are still employed, have young children and may have elderly parents to care for. The Alzheimer’s Association recommends individuals continue participating favorite activities, explore new and meaningful hobbies, join a support group, particularly one for people with early-onset, and work with a well-trained counselor. (1)
The Social Security Administration has added early-onset/ younger onset Alzheimer’s to the list of conditions under its Compassionate Allowance Initiative. This expedites access to Social Security Disability Insurance and Supplemental Social Income for individuals with the disease. (5)
(1) Alzheimer’s Association: Younger-Onset Alzheimer’s, Oct. 21, 2011
(2) Fisher Center for Alzheimer’s Research Development: Genetic Risk Factors, Oct. 21, 2011
(3) Alzheimer’s Association: 10 Signs of Alzheimer’s,. Oct. 21, 2011
(4) Genetic Health: Genetic Testing for People Without Symptoms of Alzheimer’s, Oct. 22, 2011
(5) Alzheimer’s Association: Social Security Disability, Oct. 24, 2011
Reviewed October 24, 2011
by Michele Blacksberg RN
Edited by Jody Smith