What are the types of dementia caused by Alzheimer’s disease?

Dementia is a symptom of Alzheimer's Disease in the same way that a fever is a symptom of another illness. 
Dementia includes a group of symptoms, one of which is memory loss and also includes a problem in at least one of the following cognitive functions: language, attention, problem solving, spatial orientation, judgement, planning and/or organization skills.
There are many possible causes of dementia but the most common cause is Alzheimer's Disease.  Because Alzheimer's Disease is not 100% identifiable until an autopsy after death, it is often misdiagnosed.

There are three types of dementia caused by Alzheimer’s disease:

-Early onset Alzheimer’s. This rare form of AD strikes people younger than sixty-five years old and accounts for less than 10 percent of all AD diagnoses.

-Late-onset Alzheimer’s. This is by far the most common form of AD and occurs after age sixty-five.

-Familial Alzheimer’s disease (FAD). In this extremely rare type of AD (about 1 percent of cases), the causes are entirely hereditary and onset is usually in the forties.