A fixture of morning news announced on-air today that she has what has been described as a rare blood disorder and will undergo chemotherapy and a bone-marrow transplant, TVLine.com reports.

Robin Roberts, the anchor of ABC’s "Good Morning America," has been diagnosed with myelodysplastic syndrome, or MDS. Roberts beat breast cancer five years ago.

Fortunately for Roberts, her sister is a "virtually perfect match" and will be her donor.

ABC News reported the news about Roberts on its website, including Roberts’ letter to the staff. Roberts explained that the MDS — once known as prelukemia — is likely a result of her breast cancer treatment.

Roberts is optimistic about her recovery. She wrote: “I am going to beat this. My doctors say it and my faith says it to me.”

Roberts will remain on the job for the coming months at ‘GMA,’ with some “very talented friends at ABC News” filling in on occasion. At the end of the summer or early fall, she’ll miss “a chunk of time” to have the procedure.

Robin Roberts