GMA's Robin Roberts Has Rare Blood, Bone Marrow Disorder

Good Morning America host Robin Roberts told viewers Monday that she is beginning chemotherapy for myelodysplastic syndrome, a rare blood and bone disease that she likely developed as a result of her treatment for breast cancer a half decade ago.

"My doctors tell me I'm going to beat this, and I know it's true," the 51-year-old TV anchor said on the ABC show Monday. The disease (MDS, for short) was once known as preleukemia and usually occurs in older populations, the Associated Press explains.

Bolstering Roberts' chances of a beating the disease is the fact that her sister is a near-perfect match for a bone marrow transplant, which is planned for later this summer or early in the fall. The GMA host, who scored her biggest TV get earlier this year when she sat down with President Obama to talk about gay marriage, is expected to take some time off for treatment and the transplant but plans on returning to the show when she can.

Five years ago, she was diagnosed with an breast cancer that she later beat with at least eight rounds of chemotherapy, treatment that may have caused the myelodysplastic syndrome, according to ABC's medical correspondent and other health experts.

Michelle Obama, Katie Couric, and Rob Lowe were among many friends and fans to immediately send Roberts their support via Twitter.