Last Thursday, “Good Morning America” host Robin Roberts bid a temporary farewell to her “GMA” family and audience to begin treatment for myelodysplastic syndrome (MDS), a rare blood disorder that affects bone marrow. The condition, once called pre-leukemia, is a complication from chemotherapy Roberts underwent five years ago to treat breast cancer.

Roberts announced she is leaving to start a new round of chemotherapy in advance of a bone marrow transplant later this year. “Bone marrow donors are scarce and particularly for African-American women. 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. I encourage everyone to sign up on a donor registry like bethematch.org,” Roberts said.

Roberts was joined in the emotional farewell by co-hosts Lara Spencer and Josh Elliott and her sister, Sally-Ann, who will be donating bone marrow.

Hurricane Isaac kept weatherman Sam Champion in New Orleans, but he sent warm wishes to Roberts, as did George Stephanopoulos, who was at the Republican National Convention in Tampa, Fla. He left Robert with a tap bell.

“Whatever you need, whenever you need it, ring that bell,” he said.

Roberts is determined to win this latest medical battle. MDS usually strikes older people with lethal force, but Roberts is young, strong, fit and has the best possible donor match in her sister.

Her doctors are optimistic. Dr. Gail Roboz explained the process that Roberts will undergo. “We’re hoping the first 30 days is when we’re going to see a lot of the recovery happening,” she said.

Roberts vowed to return. She shared a favorite quote with the audience: “Life provides losses and heartbreak for all of us. But the greatest tragedy is to have the experience, and miss the meaning.” She added, “I am determined not to miss that meaning.”

Roberts was due to take her medical leave a day later but left early to be with her ailing mother Lucimarian, in Gulfport, Miss. She made it home in time to say goodbye to her beloved mother, who passed away the following day at age 88.

The elder Ms. Roberts was the wife of Tuskegee Airman Col. Lawrence E. Roberts, who died in 2004. She made her own mark in history, serving as chair of the Mississippi state Board of Education in the 1980s.

She appeared on “GMA” with her daughter on several occasions. Mother and daughter collaborated on the book “My Story, My Song: Mother-Daughter Reflections on Life and Faith.”