Brenda Yim had a one-in-a-million chance of helping a little boy by giving him her bone marrow.

So she did it.

That's the kind of person she is. The mother of six is a walking poster girl for positive mental attitude.

"There was no question that I'd help," said the 47-year-old Nu'uanu resident. "It was something I had to do. As a mom, I thought what if it were me?"

She's been there. Her first daughter was born 22 years ago with a congenital heart defect. Some doctors said she might not live to see age 10.

"I know what it feels like to be up against the brick wall," Yim said. "It's so touch and go. Every day is a gift to me."

Yim, a marathon runner and triathlete, signed up to be a bone-marrow donor in 1997 after hearing about a young girl, Alana Dung, who was searching for a compatible donor. Dung, who later died, lived on the same street as Yim in Nu'uanu.

Inspired by the courage of Dung and her family, Yim decided to become a donor. She signed up with the registry, and her blood was typecast. Then last year she was called in and told that she had been selected to be a donor for an 11-month-old baby boy who had leukemia.

Without a second thought about the pain or the possible side effects from bone marrow aspiration, (the procedure includes drilling a small hole in the donor's hip bone, sucking out bone marrow and injecting it into a patient who matches genetically.) she went ahead with the procedure three days after running in the Honolulu Marathon in December.

"I felt I had to do it," Yim said. "A little hope is like a lifetime. I know."

Unfortunately, the baby died several months later. His death affected Yim, she said, as if it were one of her own children.

The chance of an unrelated donor's marrow curing someone with a blood cancer is very slim, according to the society. And the chance of being called to donate is even slimmer. In Hawai'i, only 211 people of the 66,000 who have volunteered have been called to donate. There are more than 5 million donors nationwide on a registry.

And when the Leukemia and Lymphoma Society of Hawai'i asked her to represent their 65,000 bone marrow donors in Hawai'i, she said yes again. So on Sept. 24, she and about 1,000 other people will be carrying lighted balloons, some red to represent supporters and some white representing patients, at the sixth annual Light the Night drive at Hawaiian Waters Adventure Park.

Yim was chosen to be the symbol for donors because she was a donor, said Amanda Homrighausen-Krog, campaign coordinator.

"She was a donor, one of many" Homrighausen-Krog said. "She's someone we have worked with in the community. We asked her to support the society and to do this event."

The other symbol is kite boarder Sheldon Plaventovich, who is a leukemia survivor and supporter of the society, Homrighausen-Krog said.

"We find that if people have a name and a face and story to connect to the cause they're more willing to participate and donate," she said.

"The registry is so wonderful," Yim said. "The risk seemed so small. Even though I enjoy an active lifestyle I would have adapted if something went wrong. I mean I could always walk if I couldn't run any more.

"Helping that baby was more important to me than crossing the finish line at a good time."

But she was fine after donating her bone marrow. In fact, she qualified for the Boston Marathon. Within a month, she was back to her rigorous training schedule and just last month returned from an Ironman competition in Canada.

"Any parent should feel the same way and want to help," Yim said. "It's such a simple thing to do."

Reach Suzanne Roig at sroig@honoluluadvertiser.com.