Robin Roberts Health Threat

"Good Morning America" co-host Robin Roberts is facing another major health battle.

51 year old Roberts says she has been diagnosed with myelodysplastic syndrome (MDS), a rare blood disorder affecting the bone marrow.

Experts say the bone marrow loses its ability to produce enough mature blood cells.

MDS is often referred to as pre-leukemia.

Doctors say, it might be linked to Roberts prior cancer treatment five years ago.

Roberts will receive a bone marrow transplant from her older sister later this year.

Roberts remains upbeat about her diagnosis and her prognosis.