What is Myelodysplastic Syndrome?

Myelodysplastic syndromes (MDS) are a group of diverse bone marrow disorders in which the bone marrow does not produce enough healthy blood cells. MDS is often referred to as a “bone marrow failure disorder”. MDS is primarily a disease of the elderly, but can affect younger patients as well.

In MDS, the blood stem cells (immature cells) do not become healthy red blood cells, white blood cells, or platelets. These immature blood cells, called blasts, do not work the way they should and either die in the bone marrow or soon after they go into the blood. This leaves less room for healthy white blood cells, red blood cells, and platelets to develop in the bone marrow. When there are fewer healthy blood cells, infection, anemia, or easy bleeding may occur.

Types of Myelodysplastic Syndrome

There are several types of myelodysplastic syndromes. The types are based on how the cells in the bone marrow look under a microscope. They include:

Refractory cytopenia with unilineage dysplasia (RCUD): This type affects only one type of blood cell — red cells, white cells or platelets.
Refractory anemia with ringed sideroblasts (RARS): This type involves low red blood cell counts, with or without low white blood cell or platelet counts.
Refractory cytopenia with multilineage dysplasia (RCMD): This type affects two or three types of blood cells — red cells, white cells and/or platelets.
Refractory anemia with excess blasts (RAEB): In this type, the bone marrow has too many immature white blood cells (blasts).
Myelodysplastic syndrome, unclassifiable (MDS-U): This type is diagnosed when the condition doesn't fit into any of the other categories.
Myelodysplastic syndrome associated with an isolated del(5q) chromosome abnormality: This type has a specific chromosome abnormality in the bone marrow cells.

Why do people get Myelodysplastic Syndrome?

The exact cause of myelodysplastic syndromes isn't known. Most people with MDS have no identifiable, specific cause for their disease (idiopathic). However, certain factors can increase the risk of developing the disease. These include:

Previous treatment with chemotherapy or radiation
Exposure to certain chemicals, including tobacco, pesticides and industrial chemicals such as benzene
Exposure to heavy metals, such as lead or mercury
Having a history of certain blood disorders, including aplastic anemia, or certain genetic syndromes, such as Down syndrome

While anyone can develop MDS, it's more common in people over age 60, and in men.

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What is Myelodysplastic Syndrome?

Types of Myelodysplastic Syndrome

There are several types of myelodysplastic syndromes. The types are based on how the cells in the bone marrow look under a microscope. They include:

Refractory cytopenia with unilineage dysplasia (RCUD): This type affects only one type of blood cell — red cells, white cells or platelets.
Refractory anemia with ringed sideroblasts (RARS): This type involves low red blood cell counts, with or without low white blood cell or platelet counts.
Refractory cytopenia with multilineage dysplasia (RCMD): This type affects two or three types of blood cells — red cells, white cells and/or platelets.
Refractory anemia with excess blasts (RAEB): In this type, the bone marrow has too many immature white blood cells (blasts).
Myelodysplastic syndrome, unclassifiable (MDS-U): This type is diagnosed when the condition doesn't fit into any of the other categories.
Myelodysplastic syndrome associated with an isolated del(5q) chromosome abnormality: This type has a specific chromosome abnormality in the bone marrow cells.

Why do people get Myelodysplastic Syndrome?

Previous treatment with chemotherapy or radiation
Exposure to certain chemicals, including tobacco, pesticides and industrial chemicals such as benzene
Exposure to heavy metals, such as lead or mercury
Having a history of certain blood disorders, including aplastic anemia, or certain genetic syndromes, such as Down syndrome

While anyone can develop MDS, it's more common in people over age 60, and in men.