Robin Roberts, co-anchor of "Good Morning America," returned to work on Monday after an abrupt nearly three-week-long medical leave, due in part to exhaustion from a blood and bone marrow condition.

Roberts, 51, who previously battled breast cancer in 2007, announced in early June that she had been diagnosed with a rare disorder called myelodysplastic syndrome (MDS), known in the past as preleukemia, but assured fans that her health issues would not prevent her from continuing on with her regular schedule.

A month later at the Television Critics Association conference, the ABC anchor told reporters that she expected to take a medical leave for an extended period at the end of August or beginning of September, when she is slated to undergo a bone marrow transplant from her older sister, Sally-Ann.

It came as a surprise then, when Roberts announced unexpectedly on July 31 that she was "not feeling too well." "In fact, I'm going to leave, and let you all do the rest of the program on your own," Roberts told surprised viewers from the studio of "Good Morning America," before leaving mid-way through the show. "I'm going to take a little time off, just to get some vacay. I'll see you in a couple of weeks." Weatherman Sam Champion ended the segment with best wishes for Roberts, saying, "Our Robin Roberts, we love you. Get a little rest. Take a week off, take two, then come back."

Robert's brief "vacation," during which ABC's Amy Robach filled in for her, landed her in Italy, where Roberts celebrated a friend's birthday and enjoyed a break from chemotherapy catheter.  "All I'm thinking about now is Italy. As a going away present my doctor surprised me and removed my PICC line today from my arm...sweet freedom!," Roberts tweeted before leaving for her trip.

During her break, Roberts shared photos of herself sightseeing in Venice, Rome, and Tuscany. She even tweeted a picture of herself praying at the Vatican alter, tipping off fans that she was "given special access to the Vatican in Rome."

On Aug. 20, after returning to work on "Morning," Roberts explained cheerfully, "My needle was past E when I left here a couple of weeks ago, but I've got a full tank, so watch out."

She later tweeted to her followers, "Thanks for great welcome back this AM @GMA. Going right now to tape PSA for #BeTheMatch. Bone marrow donors (like my sis) are saving lives."