MDS is a group of disorders where your bone marrow does not work well, and the blood-forming stem cells in your bone marrow fail to make enough healthy blood cells. People with MDS can lack the right amount of red blood cells, white blood cells, and platelets (the small cells that help blood to clot).
The disease happens because the bone marrow cells do not develop into mature blood cells. Instead, these blood cells stay within the bone marrow in an immature state. The symptoms and the course of MDS may vary greatly from person to person. These differences depend on which blood cells are affected.
All people with MDS have two things in common:
They have a low blood cell count for at least 1 blood cell type. This is called cytopenia.
Their bone marrow and blood contain blood cells with an abnormal shape, size, or look.