Myelodysplastic Syndromes (MDS)

Myelodysplastic syndromes (MDS) are blood cancers caused by abnormal blood stem cells. These immature cells in the bone marrow normally develop into different blood cells. The 3 main types of blood cells are red blood cells (RBCs), white blood cells (WBCs), and platelets.^1,2

In people with MDS, immature blood cells (called blasts) do not become mature or healthy blood cells. They die earlier than normal blasts. Having fewer healthy blood cells can lead to:^1,2

• Infection
• Anemia
• Easy bleeding

About 1 in 3 people with MDS develop acute myeloid leukemia (AML). This is a rapidly growing cancer of bone marrow cells. Certain types of MDS have a higher risk than others. Talk to your doctor about what your MDS type means for treatment and outcomes.^1,2

What are the different types of MDS?

The forms of MDS are defined mainly by how cells in the bone marrow look under a microscope. The criteria include:³

• How many early forms of RBCs, WBCs, and platelets show abnormal features (dysplasia)
• How many types of blood cells show low counts
• What portion of early RBCs are ring sideroblasts (cells with rings of iron deposits)
• The presence of blasts in the bone marrow or blood
• Chromosome changes in bone marrow cells

The current classification of MDS types comes from the World Health Organization. The types include:^3,4

MDS with multilineage dysplasia

MDS with multilineage dysplasia is the most common type of MDS. This type was formerly called refractory cytopenia with multilineage dysplasia. People with this type of MDS:³

• Show dysplasia in early cells of 2 or 3 blood cell types
• Show low counts of at least 1 type of blood cell
• Have a normal number of blasts in their bone marrow
• Have very few or no blasts in their blood

MDS with excess blasts

MDS with excess blasts is a relatively common type of MDS. This type was formerly called refractory anemia with excess blasts. People with MDS with excess blasts have more blasts than normal in the bone marrow and/or blood. There are also low counts of at least 1 blood cell type. This is one of the most likely types of MDS to turn into AML.³

MDS with single lineage dysplasia

MDS with single lineage dysplasia is a less common and less severe type of MDS. This was formerly called refractory cytopenia with unilineage dysplasia. People with this type of MDS:³

• Show dysplasia in early cells of 1 blood cell type
• Show low counts of 1 or 2 types of blood cells
• Have a normal number of blasts in their bone marrow
• Have very few or no blasts in their blood

MDS with ring sideroblasts

MDS with ring sideroblasts is a less common and less severe type of MDS. This was formerly called refractory anemia with ring sideroblasts. People with this type of MDS have many early RBCs with iron deposit rings around the nucleus. At least 15 percent of early RBCs are ring sideroblasts.³

MDS with isolated del(5q)

MDS with isolated del(5q) is a less common and less severe type of MDS. In this type, part of chromosome number 5 is missing in bone marrow cells. There are also often low numbers of RBCs and dysplasia in at least 1 cell type.³

MDS, unclassifiable

This is a rare form of MDS. In this form of MDS, the blood and bone marrow findings do not fit other types of MDS. For example, blood cell counts may be low but cells in the bone marrow may look normal.³

What causes MDS?

For most people with MDS, the exact cause is unknown. MDS occurs when there is a change (mutation) to the DNA of the stem cells. When this change causes increased cell growth and division, it can lead to cancer.^4,5

Mutations that lead to MDS may be inherited from your parents or caused by an outside exposure. Certain genetic conditions have been identified as risk factors for MDS. These include:⁶

• Fanconi anemia
• Shwachman-Diamond syndrome
• Diamond-Blackfan anemia
• Severe congenital neutropenia
• Dyskeratosis congenita

Outside exposures that can cause genetic mutations that may lead to MDS include:^1,5,6

• Previous treatment with chemotherapy or radiation therapy
• Exposure to chemicals like tobacco smoke, pesticides, or benzene
• Exposure to heavy metals like mercury or lead
• Old age

Who gets MDS?

There are about 20,000 new cases of MDS each year in the United States. Older age is an important risk factor for MDS. Most people diagnosed with MDS are over 70 years old. MDS is uncommon in people under age 50. Myelodysplastic syndromes are more common in men than women.⁴

What are the common symptoms of MDS?

In early stages, MDS may not cause symptoms. They are often first noticed from a routine blood test. The first symptoms are related to low numbers of healthy blood cells:^7,8

• Fatigue, dizziness, or weakness, caused by low RBCs (anemia)
• Frequent or severe infections, caused by low WBCs (leukopenia)
• Easy bruising or bleeding, caused by low platelets (thrombocytopenia)

Other symptoms can include weight loss, bone pain, and loss of appetite. But these are also commonly caused by something other than MDS.⁸

What are the treatments and outcomes for MDS?

The prognosis and treatment for MDS varies by the type. Some people with MDS show no symptoms and do not need any treatment. Other people may have more severe forms. Treatment may be needed to reduce problems caused by disease and slow progression to AML. Treatments may include:^1,4

• Blood transfusions
• Erythropoiesis-stimulating agents
• Chemotherapy drugs
• Other therapies