4-year-old viral video star beats the odds, thrives after receiving a bone marrow transplant from Iowa woman

OAKLAND, California -- Leah Carroll is just 4 years old and, like most pre-K kids, she loves to go down the slide. She loves to sing, too.

But unlike most kids, she's spent a good part of her childhood, more than 400 days, in the hospital.

Leah has a rare blood disorder: severe congenital neutropenia. She was diagnosed at birth.

Despite her illness, Leah burst onto the national scene earlier this year with a YouTube video that went viral. It shows the little girl sitting in her hospital bed, belting out the pop song "Overcomer" by American Idol alum, Mandisa.

"She does encapsulate that song. She is an overcomer," said Lindsay Carroll, Leah's mom. "It's amazing to see what a little 30 second video can do. I mean, it just blew up."

Last year, Leah received her second bone marrow transplant at UCSF Benioff Children's Hospital in Oakland, California, and she is home now from the hospital.

Doctors say her prognosis is bright. "I like to say that all the pain we went through is not wasted when we see the inspiration that's been taken for our story," said Carroll.

Since her internet debut, Leah has even met Mandisa, who penned the song that inspired her bravery.

Leah will soon meet the Iowa woman who donated her bone marrow, a teacher named Holly Robinson.

With Leah's future looking bright, her family is now focused on helping other kids and adults in need of bone marrow transplants, especially people from mixed race or minority communities.

"If you're white and from Northern European background, the likelihood of finding a match is 70 percent," said Dr. Mark Walters, the Director of the Blood and Marrow Transplant Program at UCSF Benioff Children's Hospital Oakland. "If you're African American, it drops to 19, 18 percent."

Leah has become a poster child of sorts for BeTheMatch.org and its efforts to dramatically increase the number of prospective donors.

All it takes to sign up is a simple swab of your cheek.

Doctors will then call you if your DNA sample matches that of someone in need.

People are most likely to match will a family member or someone who shares their ethnic background.