Facts About Myelodysplastic Syndromes

April 19, 2024 
This page was reviewed under our medical and editorial policy by Guido Marcucci, M.D., Chair, Department of Hematologic Malignancies Translational Science, City of Hope Duarte

Myelodysplastic syndromes (MDS) are a group of cancers that affect the bone marrow and blood cells. Patients with MDS don’t produce the proper amount of mature, healthy blood cells.

What Are Myelodysplastic Syndromes?

In MDS, blood-forming cells in the bone marrow become abnormal, which may lead to lower numbers of other healthy blood cells, particularly red blood cells. Red blood cells bring oxygen to the body, and a shortage of these cells may result in anemia.

There are several types of MDS, with their own impacts on blood cells. About one in three MDS patients may progress to acute myeloid leukemia (AML). It’s important to note that not all MDS patients will develop leukemia.

Myelodysplastic Syndromes Causes

Myelodysplastic syndromes form when some of the body’s bone marrow cells develop an abnormality that makes it difficult for them to form new, healthy blood cells. The abnormal blood cells are known as dysplastic cells. These cells not only die earlier than healthy cells, but they may also be destroyed by the body.

The exact cause of myelodysplastic syndromes is unknown. However, certain factors may raise the risk for developing MDS.

Myelodysplastic Syndromes Risk Factors

Environmental factors, inherited gene changes and acquired gene mutations over time in bone marrow and blood cells have been associated with an increased risk of MDS. The risk of developing MDS is also thought to rise with age. Non-genetic risk factors for MDS may include:

• Previous radiation therapy or chemotherapy treatments for cancer
• Exposure to lead, mercury or another heavy metal
• Exposure to some environmental or industrial chemicals, including tobacco, fertilizers and solvents

Types of MDS

There are six main types of MDS, each of which acts differently in the body. These include:

MDS with single lineage dysplasia (MDS-SLD): This is an uncommon type of MDS. Abnormalities are seen in one cell type, with low numbers of one or two blood cell types and normal levels of others.

MDS with multilineage dysplasia (MDS-MLD): Abnormalities are seen in two or three types of blood cells and low numbers of at least one cell type are found, while others are within normal levels. This is the most common type of MDS.

MDS with excess blasts (MDS-EB): MDS-EB is categorized by higher-than-normal levels of blasts in the bone marrow or blood, as well as low numbers of at least one type of blood cell. Blasts are a type of bone marrow cell in the very early stages of development.

MDS with ring sideroblasts (MDS-RS): Ring sideroblasts are an early type of red blood cell. MDS-RS is categorized by a certain percentage of red blood cells being ring sideroblasts, which are cells ringed with iron deposits. It rarely progresses to AML.

MDS with isolated del(5q): This MDS type is caused by a chromosomal abnormality and is most common in older women.

MDS, unclassifiable (MDS-U): This type of MDS is uncommon and is diagnosed when the cancer type doesn’t match any of the other MDS classification types.

The various types of MDS can be confusing, but the patient’s care team will always explain in more detail.