What is familial Alzheimer’s disease?
Last Reviewed: Feb 22, 2026Familial Alzheimer's disease (FAD) is a rare, genetic form of Alzheimer's disease, distinct from the kind we see in older adults. FAD is caused by inheriting specific mutations in one of three genes: PSEN1, PSEN2, or APP.
People who inherit these mutations typically show symptoms of Alzheimer's disease before age 65, often between 30 and 50 years of age. Because symptoms begin before age 65, FAD is also known as early-onset familial Alzheimer's disease, or young onset familial Alzheimer's disease.
People with FAD experience gradually worsening problems with memory and other mental functions, such as language, planning, reasoning, and social skills, as well as difficulties with walking and mobility. The symptoms of functional decline in people with FAD are similar to those we see in people who develop Alzheimer's disease due to causes other than genetic-familial ones.
When a parent carries an FAD mutation, the risk of inheritance is 50% each of their children. This is similar to the odds of flipping a coin—head or tails.
Close family members of an affected person often witness how FAD impacts their loved ones (parents, siblings, uncles, aunts, and cousins) across multiple generations.
Familial Alzheimer’s disease goes by many different names.
It is also known as:
Dominantly inherited Alzheimer’s disease (DIAD)
Early onset familial Alzheimer’s disease (EOFAD)
Autosomal dominant Alzheimer’s disease (ADAD)
Genetic Alzheimer’s disease
You can learn more about Familial Alzheimer’s Disease in this overview ⧉ from UCSF.