Types of Alzheimer’s disease
Last Reviewed: Feb 22, 2026In order to understand familial Alzheimer’s disease (FAD), it helps to understand a bit about Alzheimer’s disease overall.
Are dementia and Alzheimer’s disease the same thing?
No. Many people think dementia and Alzheimer's disease are the same thing, but they're not.
No. Many people think dementia and Alzheimer's disease are the same thing, but they're not.
Dementia is a broad, general term for a group of symptoms, such as problems with memory, thinking, and other cognitive functions. If they progress, these functional problems can increasingly interfere with a person’s daily activities. There are many causes of dementia, and these can be neurological diseases (of brain origin) or conditions whose origin is not neurological.
Alzheimer's disease is the most common cause of dementia. It is a progressive neurodegenerative disease characterized by the presence of amyloid plaques and neurofibrillary tangles in the brain. Alzheimer's disease is a specific disease, whereas dementia is the set of symptoms caused by the disease.
Learn more about the differences between dementia and Alzheimer's disease.
Late onset vs early onset Alzheimer's disease
Generally speaking, the biggest risk factor for Alzheimer's is age. As people get older, their risk of developing the disease increases. But families impacted by FAD genetics know that Alzheimer's disease does not exclusively affect older people.
Late-onset Alzheimer's disease (LOAD)
Late-onset Alzheimer's disease represents around 90% of Alzheimer's cases. It is the most common presentation of the disease and affects people after the age of 65.
Early-onset Alzheimer's disease (EOAD)
Early-onset Alzheimer's disease (EOAD) is less common than LOAD, and occurs in less than 10% of Alzheimer's cases.¹
It is called early-onset because people present the cognitive symptoms associated with the disease before age 65. In cases of EOAD, the disease and its symptoms tend to progress more rapidly and severely than in the late-onset presentation.
Because early-onset Alzheimer's disease is not common, there is less information and general awareness about it. People who have it often go through a long and difficult process to reach the correct diagnosis.
A small percentage (~10%) of early-onset Alzheimer's disease cases are caused by mutations in the APP, PSEN1, and PSEN2 genes.
Early-onset Alzheimer's can occur due to other causes not associated with these mutations.²
Sporadic vs familial Alzheimer's disease
In addition to late vs early onset, cases of Alzheimer's disease can be classified as either sporadic or familial.
Sporadic Alzheimer's disease
Sporadic Alzheimer's disease is the most common type and results from a combination of multiple factors, such as age-related changes, lifestyle, environmental conditions, and/or the presence of genetic risk variants (such as APOE4). Associated symptoms are usually detected after age 65, but can also begin earlier.
Familial Alzheimer's disease
Familial Alzheimer's disease (FAD), also sometimes referred to as autosomal dominant Alzheimer's disease (ADAD), is caused by mutations in the APP, PSEN1, or PSEN2 genes.
In these cases, the presence of a genetic mutation causes the person to develop the disease. People with FAD-related mutations often present symptoms between 30 and 50 years of age, but some mutations can cause an earlier symptom onset (in one’s 20s) or later (in one’s 70s or later).
Although people with FAD represent about 1% of all Alzheimer's disease cases³, affected families do not consider it rare, as they have witnessed it across multiple generations in different close family members.
It is estimated that around 45,000 people worldwide are affected by FAD. This rarity can make it hard for families to get the right diagnosis. Many family doctors and some neurologists are not familiar with FAD. If you or a close family member is having trouble getting diagnosed, contact Youngtimers for more information.
Learn more about diagnosing FAD
You are not alone
The Youngtimers community is full of other families from around the world who face FAD. At Youngtimers, we offer programs to help people in this community connect with others and learn more.
Sources
Reitz C, Rogaeva E, Beecham GW. Late-onset vs nonmendelian early-onset Alzheimer disease: a distinction without a difference? Neurol Genet. 2020;6:e512.
Sirkis DW, Bonham LW, Johnson TP, La Joie R, Yokoyama JS. Dissecting the clinical heterogeneity of early-onset Alzheimer's disease. Mol Psychiatry. 2022 Jun;27(6):2674-2688. doi: 10.1038/s41380-022-01531-9. Epub 2022 Apr 7. PMID: 35393555; PMCID: PMC9156414.
Bateman RJ, Aisen PS, De Strooper B, Fox NC, Lemere CA, Ringman JM, Salloway S, Sperling RA, Windisch M, Xiong C. Autosomal-dominant Alzheimer's disease: a review and proposal for the prevention of Alzheimer's disease. Alzheimers Res Ther. 2011 Jan 6;3(1):1. doi: 10.1186/alzrt59. PMID: 21211070; PMCID: PMC3109410.