Robin Roberts has a new health battle on her hands -- but she's ready to fight.
Five years after her breast cancer battle, the Good Morning America host, 51, announced Monday on GMA's website that she has been diagnosed with MDS or myelodysplastic syndrome -- a disease of the blood and bone marrow once known as preleukemia.
"My doctors tell me I'm going to beat this -- and I know it's true," writes Roberts. "They say I'm younger and fitter than most people who confront this disease and will be cured."
Roberts will immediately begin chemotherapy with a bone marrow transplant later this year; her donor will be her sister, she reveals. "I am very fortunate to have a sister who is an excellent match, and this greatly improves my chances for a cure," she explains.
Keeping a sense of humor about the diagnosis, Roberts reveals that she was diagnosed with MDS "on the very day that Good Morning America finally beat the Today Show for the first time in 16 years. Talk about your highs and lows!" She underwent painful extraction and bone marrow testing a few weeks ago -- when she also found out she'd landed an interview with President Barack Obama, in his now-historic interview supporting same sex marriage. "The combination of landing the biggest interview of my career and having a drill in my back reminds me that God only gives us what we can handle."
"I've been living with this diagnosis for awhile and will continue to anchor GMA," she says, adding that she'll miss "a chunk of time" during her surgery later this year.
"When I faced breast cancer, your prayers and good wishes sustained me, gave me such hope and played a major role in my recovery," she tells her supporters. "In facing this new challenge, I ask humbly for more of your prayers and love – as I will keep you in my mine and update you regularly on my condition."
This article originally appeared on Usmagazine.com: Robin Roberts: I Have Bone Marrow Disease