"We'd never even heard of it," said Jeff Mitchell, 41, of Langhorne, who lost his son Harrison to Tay-Sachs in January of 2010 when the youngster was a month away from his sixth birthday.
Mitchell and his wife Cathy, 38, are members of the parade organizing committee and also are active in the Jenkintown Tay-Sachs group.
Harrison Mitchell began to show worrying symptoms when he was six months old. He couldn't sit up, or roll over. He couldn't pinch or grasp. One day when his grandfather was babysitting, Harrison didn't appear to be able to see toys placed in front of him.
After several doctor visits with no diagnosis, the Mitchells took Harrison to an ophthalmologist who saw a cherry red spot on his retina, a sign of Tay-Sachs.
Both Jeff and Cathy Mitchell are carriers of the trait through their Irish heritage.
Jeff Mitchell didn't know he was part Irish until Harrison was diagnosed. Jeff Mitchell wasn't close to his father's side of the family and didn't know until later that his grandfather was Irish.
A child can inherit the disease only when both parents are carriers of the trait. In that case, with each pregnancy, a couple has a 25 percent chance of having a child with Tay-Sachs. Those couples have a 50 percent chance of having a child who is a carrier, but does not have the disease.
Children with Tay-Sachs (the disease most often appears in infancy) eventually lose motor skills, mental abilities, become blind, deaf, and paralyzed.
After Harrison was diagnosed, his life became a flurry of doctors appointments and hospital visits.
"He was on oxygen the last couple of years," said Jeff Mitchell, a shop foreman at a truck equipment company. "He lost vision but we weren't sure how much he could see because he couldn't talk and tell us." He couldn't walk and sometimes had seizures.
But Harrison's personality still shined through, said Cathy Mitchell, a medical receptionist.
"He had this way about him. He was magnetic," she said. "He made a lasting impression."
Harrison died in January of 2010. His parents immediately began an effort to raise awareness.
At the parade, they sold T-shirts, hats and other souvenirs to raise money for the parade. They handed out Tay-Sachs pamphlets that also were distributed at other events associated with the parade.
"The disease is one that people don't know a lot about," said Lt. Gov. Jim Cawley, grand marshal of the parade and a former commissioner in Bucks County. "If we can raise awareness and support for research, our hopes are that we can make Tay-Sachs a thing of the past."
Cawley stood in the parking lot at St. Joseph the Worker Catholic Church in Fallsington, the starting point of the parade, which wound through the streets to the end point at Conwell-Egan Catholic High School in Fairless Hills.
Nearby, the Eggert-Weiser family prepared to watch the parade. The Levittown residents - all of Irish descent - had not heard of Tay-Sachs disease.
A red-bearded Mark Weiser carried his 11 month-old daughter Riley in his arms.
"I think it's awesome," said Kathleen Eggert, Riley's grandmother, of the effort to spread the word. "Anyway you can raise awareness is a good idea."
Contact staff writer Kristin E. Holmes at 610-313-8211 or firstname.lastname@example.org.