Myelodysplastic syndrome (MDS) is a group of diseases where the bone marrow doesn't produce enough healthy blood cells. Instead, it makes too many underdeveloped cells, known as blasts. These blasts die in the bone marrow or soon after entering the bloodstream, causing too few healthy blood cells and low blood counts.

In its gentlest form, MDS may be anemia, low platelets or low white blood count, but about 10% to 20% of diagnosed...