That's thanks to a rare blood disorder, severe congenital neutropenia, diagnosed at birth. Despite her illness, Leah burst onto the national scene earlier this year with a YouTube video that went viral, one showing the little girl, sitting in her hospital bed, rocking out and singing with the pop song "Overcomer" by 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 and she is home now from the hospital.
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, and she will soon meet the Iowa woman who donated her bone marrow, a teacher named Holly Robinson.
Leah and her family are also squarely focused on helping others, kids and adults, in need of bone marrow transplants, especially in 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.
On Tuesday, there is a fundraiser in Leah's honor, a golf tournament at Poppy Ridge in Livermore. "She has no idea," said Carroll. "I told her one time, 'Honey, you're changing the world.' And she goes, 'I know.'"
Click here for more information about the Overcomer Golf Tournament.
Click here to join the marrow registry.