Myelodysplastic Syndrome (MDS)

What is myelodysplastic syndrome?

Myelodysplastic syndrome (MDS) is a rare disease of the blood, only occurring in four out of every 1 million children. While it develops in older patients (greater than 60 years old) most of the time, it can occur at any age. MDS develops in the bone marrow, the soft, spongy center of the long bones that produces the three major blood cells:

  • white blood cells to fight infection
  • red blood cells that carry oxygen
  • platelets that help blood clot and stop bleeding

MDS occurs when the bone marrow does not properly produce sufficient numbers of healthy red blood cells, white blood cells and platelets. With this disease, the blood cells lose their ability to mature and function properly. 

In normal bone marrow, the growth and development of blood cells are carefully controlled to produce the correct number of each type of blood cell to keep the body healthy.

All blood cells (white blood cells, red blood cells and platelets) originate in the bone marrow from a single type of cell, called a stem cell. Stem cells make up a very small portion of all the cells in the bone marrow. When more cells are needed, the bone marrow activates stem cells to rapidly produce more blood cells. In MDS, this process by which a stem cells matures into a red or white cell or a platelet is disturbed. Red and white blood cells may mature but not normally or in sufficient numbers. Sometimes, the number of immature blood cells, called blasts, increases and the number of mature cells goes down. As the disease progresses, these blasts continue to increase and invade the bone marrow, preventing them from working effectively.

MDS used to be called “smoldering leukemia” or “pre-leukemia,” but only about one-third of cases of MDS actually progress to childhood leukemia, a cancer of the blood and bone marrow.

What are the different types of MDS?

Physicians have identified several sub-types of MDS, based on how blood and marrow cells appear under the microscope. The hallmark of MDS is dysplasia, which describes the abnormal and bizarre-looking cells under the microscope. The cells used to be normal, precursor cells that produce white blood cells, red cells or platelets. When MDS develops, these cells have an abnormal appearance. Pediatric MDS is largely classified by the fraction of blasts (immature white blood cells) found in the marrow and blood. Importantly, the subtypes that have been identified in children are somewhat different from the ones that physicians are using for adults and older people.

The types of pediatric MDS are:

  • refractory cytopenia of childhood (RCC): less than 5 percent blasts in bone marrow. However, it can be normal to have a small number of blasts even in healthy bone marrow (up to 5 percent).
  • refractory anemia with excess blasts (RAEB): 5 to 20 percent of blasts in the bone marrow
  • RAEB in transformation (RAEB-t): 21 to 30 percent of blasts in the bone marrow

When the amount of blasts in a child’s bone marrow exceeds 30 percent, the condition is considered to be acute myelogenous leukemia (AML), which is a type of leukemia characterized by an increase in a particular type of white blood cell. AML that has developed after MDS is, in general, much harder to cure than de novo AML (regular AML that started anew, without any underlying MDS or other disease).

How we care for MDS

Children and young adults with MDS are treated at Dana-Farber/Boston Children's Cancer and Blood Disorders Center through our Bone Marrow Failure and Myelodysplastic Syndrome Program, recognized as one of the nation’s best pediatric treatment and research programs for bone marrow failure, MDS, and related conditions.

Your child will have access to advanced diagnostic evaluations and treatments, including individually tailored stem cell transplantation and ongoing clinical trials that are investigating new treatments. Our program also has been designated a “Center of Excellence” from the MDS Foundation — the only large pediatric center in the country awarded this designation.

Our areas of research for MDS

At the moment, very little is known about the initiating events that lead to MDS; therefore, limited specific therapies exist, and a hematopoietic stem cell transplant is currently the only treatment that can cure the disease.

Dana-Farber/Boston Children's received grant funding from the National Institutes of Health (NIH) to establish the first nationwide Pediatric MDS and BMF Registry. Over the last three years we have collected information on over 150 patients with MDS and BMF disorders. For the first time this will allow researchers at Dana-Farber/Boston Children's and collaborating institutions to collect clinical information and tissue samples to help us better understand this condition. Along with other centers we have recently identified genetic causes for several families with familial MDS. Ultimately, we hope to identify new therapies for this condition, which is currently cured only with a bone marrow transplant.

To learn more about participating in the registry, please call 888-5-pediMDS or email us at For more information, visit our website:

MDS clinical trials

For many children with rare or hard-to-treat conditions, clinical trials provide new options. Search our open clinical trials. For more information on clinical trial availability, email us at We can help you navigate your options.