(CNN) - "Good Morning America's" Robin Roberts is bravely facing a new health battle.
The 51-year-old revealed Monday that five years after overcoming breast cancer, she's been diagnosed with a rare blood disorder that affects the bone marrow called myelodysplastic syndrome, or MDS.
"My doctors tell me I'm going to beat this, and I know it's true," Roberts said in a statement Monday, explaining that the disease was once known as "preleukemia." Her doctors tell her she's "younger and fitter than most people who confront this disease, and will be cured."
Roberts starts pre-treatment today, and thankfully her sister is a bone marrow match, which "greatly improves my chances for a cure," she noted.
The "GMA" anchor was diagnosed on the same April day that the ABC program pulled ahead of NBC's morning show, "Today," for the first time in 16 years.
"Talk about your highs and lows!" she said in her statement, adding that she's been living with the diagnosis for a while, and plans to continue her work with "GMA."