Allie Tarzwell has a photo album full of good times. She's been to Tennessee, Texas, Disneyworld, the race track, even swimming with dolphins. She also won gold and silver medals at the Special Olympics.
It's been an adventure for her mother, Gayle, too. But with all the joy comes worry.
Forty percent of people with Down syndrome develop Alzheimer's disease by age 40. That number increases to 50 percent by age 50.
Today, Allie is 32.
"It's coming at us fast is how I look at it," Gayle Tarzwell said.
Dr. Brian Skotko knows the numbers. He's the director of the Down syndrome program at Massachusetts General Hospital.
"There's an urgency because they love their person with Down syndrome so much that they don't want to lose any of that. They don't want that personality to be lost to Alzheimer's," Skotko said.
Skotko's patients have three copies of chromosome 21, the same chromosome linked to a build-up of sticky proteins or plaques that can lead to Alzheimer's. People without Down syndrome have just two.
"When people with Down syndrome have an extra copy, they build up those plaques faster," Skotko said.
The first symptoms often involve changes in behavior. People with Down syndrome can become irritated and depressed. Some experience seizures. The memory loss associated with Alzheimer's occurs later but it's just as devastating.
"So it's really prevalent in our population and it's a pressing concern because right now, we have no treatments for Alzheimer's itself. I think what we can learn from people with Down syndrome can help all of us," Skotko said.
Allie is now part of a national clinical trial to test the safety of a new vaccine that may activate a patient's immune system to attack the plaques before they build up. Patients in the trial receive seven shots in one year and won't know if they're getting the vaccine or a placebo.
Allie and her mother say the decision to sign up was easy.
"We just knew we had to help out. Had to be part of the solution, not just for us but for other people out there that are at risk of having Alzheimer's disease, whether they have Down syndrome or not," Gayle Tarzwell said.