“Good Morning America” anchor Robin Roberts made some news of her own today: She’s been diagnosed with a rare blood and bone marrow disease called myelodysplastic syndrome (MDS), a condition once known as pre-leukemia.  Roberts, a breast cancer survivor, said she received the diagnosis several months ago and will receive a bone marrow transplant from her older sister later this year. “My doctors tell me I’m going to beat this – and I know it’s true,” she wrote when she announced her diagnosis.MDS is a pre-cancerous disorder half way between benign and malignant, said Dr. Martin Tallman, chief of the leukemia service at New York’s Memorial Sloan-Kettering Cancer Center. It occurs when the bone marrow produces blood cells that break apart and disintegrate when they enter the blood stream.

 “When the marrow produces blood cells, they’re cracked, they’re fragile and faulty and they disappear, he said.  Those disappearing blood cells leave patients with a low blood count, Tallman told msnbc.com, which can leave patients feeling fatigued from anemia, susceptible to infections like pneumonia and suffering from internal bleeding. The condition is curable, though it can also lead to fatal complications, primarily through infection, and some MDS patients develop leukemia. 

MDS is more common in people over 60, and in most cases, doctors don’t know why they developed the disorder, though genetic changes that take place as people get older are thought to be the cause. A minority of MDS patients develop the disorder following chemotherapy for cancer treatment.

 “Sometimes treatment for cancer can lead to other serious medical issues and that’s what I’m facing right now,” Roberts said on the air this morning, noting that she beat breast cancer five years ago.  Tallman explains that as chemotherapy drugs are killing cancer cells, they can also cause genetic changes in healthy cells, which can lead to what’s called treatment-related MDS. “We are able to cure certain disease but we pay a price,” he said.

About 12,000 people a year are diagnosed with MDS in the U.S. each year, according to the American Cancer Society. The number of cases of MDS is rising, according to the Memorial Sloan-Kettering website, because there is a growing population of older people, and because patients are living longer after being treated for their first cancer.

For years, patients with MDS were treated with antibiotics and blood transfusions, but three new types of chemotherapy drugs to fight MDS became available starting in about 2004, said Tallman, a hematologist-oncologist. They are effective in about 30 percent to 40 percent of patients, he said. Some patients don’t require treatments at all and can live with the disease; others are cured with the chemotherapy drugs alone. The only proven cure for MDS is a stem cell transplant, Tallman said, describing what it also called a bone marrow transplant.

Roberts says she is beginning a pre-treatment regimen of chemotherapy today before undergoing the bone marrow transplant. Her doctors gave her a good outlook, she wrote.

“They say I’m younger and fitter than most people who confront this disease and will be cured.”