Myeloblasts are immature forms of white blood cells that do not develop into mature white blood cells. Therefore, they do not function correctly. Myeloblasts do not normally appear in the bloodstream.
It is possible for a person to have a low amount of myeloblasts in the bone marrow and not go on to develop MDS or AML. However, a person in good health will not typically have any myeloblasts in the bone marrow.