With myelodysplastic syndrome why does the body stop producing healthy blood?

Stem cell problem: Myelodysplastic syndrome is a problem with the bone marrow forming or blood stem cells where the bone marrow does not function normally. There is a disordered production and maturation of the different types of blood cells (white blood cells, red blood cells and platelets) which leads to a decrease in the amount of one or more of these cell types circulating in the blood.

See below...: The bone marrow (where blood elements are produced) has high cellularity in mds, similar to leukemia. However, unlike leukemia, most of these abnormal cells cannot get out of the marrow into the peripheral blood (ineffective hematopoiesis). Consequently, the peripheral blood cell counts are abnormally low (cytopenia), unlike leukemia where the white blood cell count is usually highly elevated.