"Good Morning America" co-anchor Robin Roberts underwent a bone marrow transplant yesterday, months after announcing her diagnosis with the rare blood disorder myelodysplastic syndrome. The 51-year-old Roberts has spent 11 total days under the care of physicians which found her undergoing chemotherapy that is necessary to prepare her for the transplant. The charismatic co-host took to Twitter to keep her friends, family, and followers up-to-date with the latest, tweeting, "Just completed chemo[therapy]. Today is day of rest — positive thoughts, words and deeds. How every day should be. Love you from bottom of my grateful heart."

Myelodysplastic syndrome, formerly known as preleukemia, is a condition where the bone marrow does not produce enough healthy blood cells, according to the National Cancer Institute. Common treatments include medication and bone marrow transplant, like the one Roberts will have. In Roberts' case, she is receiving bone marrow stem cells from her sister, who was found to be a match. The National Institute of Health reported that the actual transplantation usually does not require surgery; the donor's stem cells are delivered to the patient's body via a central venous catheter. People can become marrow donors by registering with the Be the Match registry. According to the most recent registry data, transplants that were conducted via donors from this registry increased between 2005 and 2010 from 2,600 to 5,200.