"Good Morning America" host Robin Roberts, who famously battled — and beat — breast cancer five years ago, revealed to viewers today that she is now facing another serious health issue.


Roberts was diagnosed with MDA, or myelodysplastic syndrome— once known as preleukemia — the same day that ABC found out "Good Morning America" trumped the "Today Show" in ratings for the first time in six years.


What should have been a celebratory time for Roberts, was interrupted with the grim news that marked the start of a battle against the serious blood and bone marrow disease. Roberts, 51, told viewers today in a statement that she is determined to beat MDA and her doctors have faith that she can.


"If you Google MDS, you may find some scary stuff, including statistics that my doctors insist don’t apply to me. They say I’m younger and fitter than most people who confront this disease and will be cured," Roberts said in a statement.


Roberts has begun chemotherapy in preparation of a bone marrow transplant later in the year. Though donors can often be scarce, particularly for African American women, Roberts' sister is a perfect match.

Roberts said she plans to maintain her presence on "Good Morning America" every day, though she may have to miss an occasional day and eventually a "chunk of time" when she undergoes her bone marrow transplant.

"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 said. "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."