SAN DIEGO -

Jonathan Shirley has Down syndrome, but he's never let what he can't do hold him back.

"I don't look at disabilities at all. I look at what I can do," Shirley said.

Jerry Shirley, his dad, said Jonathan is always finding ways to help others.

"Jonathan is an amazing guy. He's been an inspiration," he said.

Shirley is now helping doctors at the University of California San Diego not only learn more about his condition, but also about Alzheimer's disease.

"These individuals, when they hit the age of 40, 100 percent of them have the pathological changes of Alzheimer's disease in their brain," said Dr. Michael Rafii, a neurologist at UCSD.

As part of a clinical trial, Rafii has found Down syndrome brains look very much like Alzheimer's brains. Both have higher levels of the protein beta amyloid. In fact, Down syndrome patients develop the protein at double the rate.

"We may be able to translate those discoveries into therapies for the general population. People with Down syndrome represent the world's largest population of predetermined Alzheimer's disease from a genetic perspective," Rafii said.

Lisa Goldberg, 61, has Down syndrome and her sister said she is also now showing some signs of dementia.

"Something that happened five minutes ago, it's hit or miss whether she recalls," said April Hinson, Goldberg's sister.

Goldberg still works, not letting her disability get in her way.

And Shirley agreed: "We are all special in our own way."

It just may be that Down patients like Shirley and Goldberg hold the key to finding the answer to Alzheimer's.

Raffi’s research is now focusing on how somebody can have amyloid plaques in his brain and have full dementia, whereas someone else has the same amyloid plaque but no dementia. Rafii believes there is something some patients have in their brains that makes them resilient to it.

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