COSTA MESA — Members of Costa Mesa High School's Class of '84 will gather Saturday morning in Irvine to raise awareness about Lou Gehrig's disease, which afflicts one of their classmates.

A group of nearly 60 is expected to take part in the three-mile walk, organized by the ALS Association, that starts at 8:30 a.m. at William R. Mason Regional Park.

Dubbed "Class of '84 for Nancy!", the group was formed in support of Nancy Polisso, 44, who was diagnosed with Lou Gehrig's disease — also known as amyotrophic lateral sclerosis (ALS) — more than two years ago.

"I can't even put into words, when diagnosed with a terminal illness and faced with your own mortality, how amazing this is," Polisso said.

Polisso, who now lives in Northern California, will cut the ribbon to launch the walk.

"That the people you started your life with — and I've known these people my whole life, although a lot of them have moved away over the years, myself included — the way that my friends have come together, it's like they never left," Polisso said.

So far the group has raised $2,050 toward its $3,000 goal.

About 2,000 people and 100 teams have signed on for the walk, which aims to raise $225,000 for research and support groups.

"There is no cure for ALS," said Keith Regan, executive director of the ALS Association's Orange County chapter. "There have been some major breakthroughs, but we are still a long way away from finding a cure."

About 5,600 people nationwide are diagnosed each year and as many as 30,000 people have the disease at any given time, according to alsa.org.

Last-minute sign-ups are encouraged and can be done online or in person, Regan said.

"If you want to come out and give a good feeling for someone going through real rough time and help their families, it's a great way to do it," Regan said. "To let them know not they're alone in their fight and we're all in this together."

sarah.peters@latimes.com

Twitter: @speters01

If You Go

What: 12th annual Irvine Walk to Defeat ALS

When: 8:30 a.m. Saturday

Where: William R. Mason Regional Park, Culver and University drives, Irvine

Information: http://www.alsa.org