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OTRC: Robin Roberts: 9 facts about 'GMA' anchor's MDS and bone marrow transplant

Robin Roberts talks to OTRC.com in 2011.

Robin Roberts, co-anchor of ABC's "Good Morning America," is set to soon undergo a bone marrow transplant to treat myelodysplastic syndrome, a rare blood and bone marrow disorder.

On Thursday's episode, the 51-year-old announced she will begin her medical leave on Friday, a day earlier than scheduled, citing a last-minute plan to visit her ailing mother. The co-anchor of the morning show revealed her MDS diagnosis in June, saying it was caused in part by treatments she had undergone for breast cancer five years ago. Her sister, Sally-Ann, is her bone marrow donor.

Check out 9 facts about Robin Roberts, her MDS and upcoming bone marrow transplant.

1. Myelodysplastic syndrome - what is it?

Bone marrow contains stem cells, which are supposed to mature into red blood cells, used to carry oxygen throughout your body, white blood cells, which fight infections, or platelets, which help your blood to clot. According to the National Cancer Institute, people who have myelodysplastic syndromes do not possess enough healthy stem cells and may suffer from complications such as bleeding, anemia or infection.

MDS is often dubbed a "pre-leukemia." Left untreated, it can progress to acute myeloid leukemia, a cancer that forms inside bone marrow. Transplants are also carried out for patients suffering from blood cancers and lymphomas, which attack the immune system.

2. Myelodysplastic syndrome - symptoms.

The National Cancer Institute says symptoms of MDS include shortness of breath, fatigue, pale skin, easy bruising or bleeding and small spots under the skin that are caused by bleeding, fever and frequent infections.

3. Myelodysplastic syndrome - risk factors.

Robin Roberts has said her disease was caused in part by treatments she had undergone for her breast cancer. Chemotherapy and radiation therapy are among the risk factors for MDS. The National Cancer Institute says being male, white or older than 60 and past exposure to chemicals such as tobacco smoke, pesticides, and solvents as well as heavy metals can also increase the chances of contracting the disease. An average of 3.4 out of 100,000 people will be diagnosed every year, the group says.

4. Myelodysplastic syndrome - can be both caused by and treated with chemotherapy

Roberts had been treated with chemotherapy for her breast cancer five years ago and suffered the side effect of losing her hair. While chemotherapy can help cause MDS, is it is also often used to treat it. It is administered by mouth or IV and uses drugs to try to stop immature blood cells from growing or dividing. Roberts has already undergone mild chemotherapy ahead of her bone marrow transplant.

She told her doctor on Thursday's show: "I went through pre-treatment with you and it was a mild form of chemotherapy, that I didn't lose my hair or anything like that and people remember at the end of july, I had a really bad day on the air with a clenched jaw."

5. A bone marrow transplant is the most effective treatment for MDS.

The procedure is more likely to lead to a long-term remission from the disease than any other treatment because it replaces the abnormal cells in a person's blood with healthy ones from their donor.

"With cancer patients, we use five years as a benchmark to a cure," Roberts' doctor, Gail Roboz, told ABC News. When someone has had a marrow transplant, we'll be watching her for life, to see if she's having symptoms."

6. Bone marrow transplant - overview of the procedure.

Sally-Ann had some of her healthy stem cells harvested ahead of the co-anchor's transplant. They will be infused via a catheter into her sister's blood, where they are expected to make their way into her bone marrow and mature into healthy red or white cells or platelets that will replace the unhealthy stem cells the chemotherapy is supposed to attack.

The production of new cells is called "engraftment" and it occurs between two and four weeks after the transplant. During this time, the patient's immune system is particularly weak and antibiotics are administered to protect them from infection.

"There's going to be a special IV put in, there are going to be a few days of chemo and then there's going to be the transplant, which is infused through the special IV," Roboz said. "It looks like a bag of blood. And you wouldn't really know we were doing anything if we didn't tell you. You could sleep through the whole thing."

6. The first 30 days of Roberts' treatment are particularly important.

"We look at those first 30 days out as the time to rebuild your systems. So we wiped out your bone marrow, we wiped out your immune system but Sally-Ann's have got to find their way into that catheter, swim around, figure out where to go and set up shop in you so that you get functioning blood and a functioning immune system again," Roboz told Roberts on the show.

"We're hoping the first 30 [days] is when we're going to see a lot of that recovery happing and we're protecting you during that time," the doctor added. "You're getting some blood and antibiotics to protect your system until you're up and running again."

7. People who receive bone marrow transplants are typically kept in isolation after the procedure.

After a bone marrow transplant, patients are usually put in an isolation area because their white blood cell count is so low and their body will therefore have trouble fighting off a potential infection, which could be spurred as a result of contact with viruses and bacteria. After they are released from the hospital, they are typically told to avoid public places or wear masks. This also applies to their visitors.

"I I love you, sister, and I'm going to be with you in that isolation area, wearing my mask," Sally-Ann told Roberts on Thursday's episode.

8. Bone marrow transplants have a long recovery time for patients, short one for donors.

"If all goes well, Robin will go home after 30 days," her doctor told ABC News. "When she goes home she won't be feeling like herself, but we hope she'll be able to do some exercises, read and focus."

Bone marrow transplant recipients remain in the hospital in isolation until a doctor determines their white blood cell count is high enough. The timeframe for such a hospital stay varies for every person, who undergo blood tests continuously.

"Starting at that 30-day mark, she'll have bone marrow evaluations to see that it's growing normally," Roboz told ABC News. "In the days that follow - until the 100 day benchmark - we're seeing problems getting solved. She'll get off the meds, she won't feel as tired or as gross as you do when you're on so many pills. She'll start liking to eat again. She'll have to remind herself what she likes to do. You're separated from all that stuff for so long, you have to slowly reintroduce yourself to what you used to do."

After bone marrow recipients are released home, they must return for treatments, which could continue for several months. Transplant patients in general usually cannot return to work for up to six months. Those receive a bone marrow donation from a sibling may not regain complete function of their immune system for up to two years.

Roberts told her doctor: "I'm not even going to ask you when I can come back because you have said, 'Don't put a timetable on it' and just know that I'm going to get back here as soon as I can."

Donors, however, can recover fully and resume their normal routine fairly quickly - the time varies between two days and four weeks.

"I'm feeling just fine. My heart is with you right now and it's also with all the people in my community who are going through Isaac in New Orleans," Sally-Ann told Roberts on "GMA." "I'm going to be back on the air on Saturday on my station and so that's what people need to know - that the recovery time is so very quick. I feel 100 percent."

9. Robin Roberts' procedure is called an allogeneic transplant - because her sister is her donor.

In such bone marrow transplants, stem cells are donated to a patient by a parent or sibling that is not a twin or by a person unrelated to them. The National Cancer Institute says brothers and sisters are more likely to be a match and that up to 35 percent of patients have a sibling that is one.

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