An 11-year-old girl who beat a rare bone marrow disorder is now battling bone cancer.
Hallie Barnard, from Denton, Texas, was born with Diamond-Blackfan Anemia, which is when the bone marrow doesn't make enough red blood cells, decreasing the amount of oxygen flowing through the body.
The only cure is a bone marrow transplant and, after about nine years of searching, a match was found, Good Morning America found.
In the midst of this battle, she and her family set up Hallie's Heroes in July 2015 to help fund research for bone marrow issues and host bone marrow drives to encourage more people to sign up for the registry.
But in March, just four months after her transplant, a lump formed on Hallie's left leg, which doctors confirmed was a cancerous tumor.
In addition to chemotherapy, doctors told the Barnards that Hallie's leg bone was weak and would likely break so, last month, her leg was amputated above the site of the tumor.
Despite her medical issues, Hallie is still helping out at the nonprofit, speaking to crowds of thousands to register for the bone marrow registry and raising money to help the families of kids battling cancer.
Hallie Barnard, 11 (left and right), from Denton, Texas, was born with Diamond-Blackfan Anemia and was diagnosed at 15 months old. DBA is a disease in which the bone marrow can't make enough red blood cells
DBA is so rare that only 30 kids are diagnosed in the US and Canada each year, and the only cure is a bone marrow transplant. Pictured: Hallie (far left) with her parents and siblings
When Hallie was a newborn, her parents said they knew pretty quickly that something was wrong, according to a Facebook post.
She didn't gain weight quickly, colds would linger for more than a month and she would not sleep often.
When she was one year old, she was tested for anemia at her check-up, which came back positive.
At 15 months, she was finally diagnosed with Diamond-Blackfan Anemia (DBA).
DBA is a disease in which the bone marrow can't make enough red blood cells to meet the body's needs
This is important because red blood cells carry oxygen throughout the body. A lack of oxygen was behind Hallie's symptoms.
The disease is caused by mutations in one of several genes, which provide instructions for making proteins
It's so rare that only 30 cases are diagnosed in the US and Canada each year, according to Stanford Children's Health.
Treatments include corticosteroid drugs, to make the bone marrow produce more red blood cells, and blood transfusion, to replace blood cells.
However, the only cure for DBA is a bone marrow transplant.
After years of searching for a donor, Hallie