Early Onset Alzheimer's Q and A

July 31 -- Also known as "the long goodbye," Alzheimer's isn't always a disease for the old. For a small number of individuals, it strikes while they are in the prime of life — sometimes as early as their 30s.

Early onset Alzheimer's disease, designated by its incidence under the age of 60, afflicts about 200,000 Americans or about 5 percent of the estimated four million who suffer from AD.

ABCNEWS asked several Alzheimer's experts to discuss early onset Alzheimer's detection and diagnosis as well as the challenges that those diagnosed with the disease may face.

How is early onset Alzheimer's diagnosed?

The diagnosis of dementia is the same as in the late form of AD. This involves ruling out other forms of dementia and diseases that cause secondary dementia (brain tumor, for example). Imaging has assisted the diagnosis. Inherited forms of AD can be detected by genetic testing. — Dr. Sid Gilman, William J. Herdman professor and chair of the department of neurology at the University of Michigan in Ann Arbor.

What role does genetics play in early onset Alzheimer's?

There's a lot of focus on the genetic angle because there are now three known genes that are mutated in some families, leading to the occurrence of early-onset AD. These genes are enormously important because we know what they are and, to some degree now, what they do. So this gives us important clues to how the disease develops. But the mutations are rare! There are almost certainly other genes, as yet unknown, that can cause early onset AD in some families. The problem is, they are probably even more rare than the ones that are known, so it's even harder to find them. — Dr. John C. S. Breitner, professor and head, of the division of geriatric psychiatry at the University of Washington School of Medicine in Seattle.

Are there any challenges to detecting early onset Alzheimer's?

Unless there is a strong family history — present in probably no more than half of these cases — the disease is somewhat harder to diagnose. Unlike late-onset AD, which is the predominant form of late-life dementia, early-onset AD is only one of many causes of dementia in middle life or before. All are rare, so one can't rely on such dictums as 'if it's dementia, its Alzheimer's disease until proven otherwise.' — Dr. John C. S. Breitner, professor and head, of the division of geriatric psychiatry at the University of Washington School of Medicine in Seattle.