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"Good Morning America" co-host Robin Roberts announces she has myelodysplastic syndrome

TV personality Robin Roberts arrives at the 84th Annual Academy Awards held at the Hollywood and Highland Center on Feb. 26, 2012 in Hollywood, Calif. Ethan Miller/Getty Images

(CBS News) "Good Morning America" co-host Robin Roberts announced today that she has been diagnosed with myelodysplastic syndrome (MDS), more commonly known as preleukemia.

"My doctors tell me I'm going to beat this -- and I know it's true," she wrote in a letter to her colleagues, later posted on the ABC blog.

Pictures: Robin Roberts

Going forward, Roberts - who previously beat breast cancer five years ago - said on Monday's "Good Morning America" that she will begin pre-treatment, which consists of chemotherapy. She warned fans that she would start today and to not to be alarmed if they saw her wearing a bandage tomorrow. Roberts added on Monday's show that she will eventually receive a bone marrow transplant later this summer or fall from her sister.

According to the National Cancer Institute, MDS is a group of diseases where bone marrow does not produce healthy blood cells. The patient's age - typically over 60; - and past treatment with chemotherapy or radiation therapy increases the risk of developing the disease. Other factors include being white or male, being exposed to certain chemicals - including tobacco smoke, pesticides and solvents - or being exposed to heavy metals, such as mercury or lead increase the risk of getting myelodysplastic syndrome.

Symptoms of the disease include feeling tired, shortness of breath, having skin that is paler than usual, easy bruising or bleeding, petechiae - or flat pinpoint spots under the skin caused by bleeding - and fever or frequent infections.

Typical treatments for the disease also include supportive care, which consists of blood transfusion therapy, other types of drug therapy and the use of erythropoietin, known to increase red blood cells and help curtail the effects of anemia.

Roberts said that she has known of her diagnosis for quite some time, and will continue to anchor "Good Morning America" while she is receiving treatment. She first found that she had the disease in April, the day it was announced that "Good Morning America" beat the "Today Show" in ratings for the first time in 16 years. Roberts then had a procedure bone marrow extraction procedure the day before she was to interview President Barack Obama.

"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," she wrote.

Roberts encouraged people to become bone marrow donors to help save the lives of people in similar situations.

"Bone marrow donors are scarce and particularly for African-American women," Roberts said. "I am very fortunate to have a sister who is an excellent match, and this greatly improves my chances for a cure. As you know from my recent interview with Mark Zuckerberg, organ donation is vitally important. Many people don't realize they can be bone marrow donors."

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