(Refiles to fix typo in headline)
NEW YORK, Feb 20 (Reuters) - Robin Roberts, a co-host of ABC's "Good Morning America," returned to the popular morning news show on Wednesday, five months after a bone-marrow transplant for a rare blood disorder that was triggered by cancer treatment.
Roberts, 52, was welcomed back with a special edition of the show that began with a taped message from President Barack Obama and his wife, Michelle.
"Good morning, America, and welcome back, Robin," the first lady said.
Roberts said she had waited 174 days to return to the show and was pinching herself so she knew it was real.
"This is really happening," she said. "Faith, family and friends have brought me to this moment and I am so full of gratitude."
Roberts took a medical leave of absence in August to fight the blood disorder myelodysplastic syndrome. Five years earlier she had been treated for breast cancer.
ABC News announced that Roberts will interview Mrs. Obama later this week for next Tuesday's show. The first lady's program to fight childhood obesity will be among the topics.
"Robin, we just want you to know that the whole Obama family, we've been thinking about you and praying for you and rooting for you every step of the way," Mrs. Obama said in the message.
Oprah and former U.S Secretary of State Hillary Clinton were among the celebrities who offered Roberts their best wishes on her return to "Good Morning America," which has bumped NBC's "Today" show from the top spot in the ratings last year.
The show has remained ahead while Roberts was away as guests co-hosts filled in for her.
Roberts said she first realized something was wrong with her health a year ago while covering the Academy Awards in Los Angeles. She saw a doctor after suffering from exhaustion and the blood disorder was discovered.
Her doctors said they will monitor her condition to make sure she does not overdo it. The nurses and doctors who cared for her were on the show Wednesday, along with her siblings and friends. (Reporting by Noreen O'Donnell; Editing by Patricia Reaney and Bill Trott)