What Are Myelodysplastic Syndromes?

This content has been reviewed and approved by

Hagop M. Kantarjian, MD
Chairman & Professor, Leukemia Department
MD Anderson Cancer Center
University of Texas

Myelodysplastic syndromes (MDS) are a group of diseases marked by abnormal production of blood cells by the bone marrow.

About 10,000 to 15,000 new cases of MDS are diagnosed each year in the United States, usually in people older than 60.

Healthy bone marrow produces immature blood cells—called blasts—that then develop into red blood cells, white blood cells, and platelets. 

MDS disrupts this normal process so that the bone marrow is overactive, but not efficient. This means it does not produce enough of the good cells needed by the body, such as red blood cells to carry oxygen, white blood cells to fight infections, or platelets to protect against bleeding. 

These blasts, in time, may not fully develop into mature blood cells. As a result, patients with MDS have fewer mature blood cells, and those they do have may be abnormal and not function properly. Also they may progress into acute leukemia when the blasts are more than 20 percent to 30 percent of total cells.