(CNN) -- Five years after battling and beating breast cancer, "Good Morning America" co-anchor Robin Roberts faces another dangerous health foe.
"I've always been a fighter, and with all of your prayers and support, a winner," Roberts said in an online message Monday.
Roberts, 51, was diagnosed with myelodysplastic syndrome, also called MDS, on the same day in April that her show beat out NBC's "Today Show" in the ratings for the first time in nearly 16 years, she said. "Talk about your highs and lows!"
"Then a few weeks ago, during a rather unpleasant procedure to extract bone marrow for testing, I received word that I would interview President Obama the next day," Roberts said. "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 and that it helps to have a good sense of humor when we run smack into the absurdity of life."
MDS is "a disease of the blood and bone marrow and was once known as preleukemia," Roberts said in her message on the ABC News website.