Question: What is early-onset Alzheimer's, and how does it differ from regular Alzheimer's disease?
Answer: Alzheimer's disease probably is the very same process in the brain no matter the age at which the symptoms begin. That is, a person who has late-onset Alzheimer's disease likely has the very same brain changes as someone who has early-onset Alzheimer's. However, the difference with early-onset Alzheimer's disease is that, the younger the age at which symptoms occur -- the dementia occurs -- the more likely it is to be a clear genetic cause of Alzheimer's disease.
Whereas, most all individuals in late-life Alzheimer's have age as their major risk factor with perhaps a component of the genetic risk, but not caused by a genetic problem.