Myelodysplastic syndromes (MDS) are cancers that affect blood cells in the bone marrow. In MDS, blood cells don’t develop normally. This means there are fewer healthy blood cells in your body.

Keep reading to learn more about MDS, symptoms to look out for, and how it’s diagnosed and treated.

MDS refers to a collection of cancers that impact myeloid stem cells in your bone marrow. Normally, these stem cells go on to make:

  • red blood cells (RBCs) that carry oxygen throughout your body
  • white blood cells (WBCs) that respond to infections
  • platelets that help blood to clot

In MDS, some types of stem cells don’t develop properly and appear abnormal, or dysplastic. MDS also leads to higher numbers of immature blood cells in your body. These immature cells are called blasts.

Blast cells either die quickly after being produced or don’t function very well. They also crowd out the healthy blood cells that you do have. This crowding most commonly affects RBC levels, leading to anemia.

Some types of MDS can go on to transform into acute myeloid leukemia (AML). AML is a type of leukemia that can grow and progress rapidly if it isn’t treated.

The exact cause of MDS is unknown. But genetic changes, either inherited or acquired over your lifetime, appear to play a big role. Known risk factors for MDS are:

  • older age
  • assigned male at birth
  • previous treatment with chemotherapy
  • a family history of MDS
  • certain genetic conditions, such as Fanconi anemia
  • high exposure to radiation or certain industrial chemicals

Some people with MDS may not have any noticeable symptoms. In this case, MDS may be detected during routine blood testing or testing for other health conditions.

Many of the types of MDS have overlapping symptoms. Symptoms happen due to a decrease in healthy blood cells in the body and can include:

See a doctor if you have any of the symptoms above, particularly if they cannot be explained by a known health condition. The doctor can help determine if your symptoms are caused by MDS or something else.

The World Health Organization (WHO) currently recognizes 6 types of MDS divided up based on characteristics like:

  • whether cells look abnormal under a microscope (dysplasia)
  • the presence of low blood cells counts (RBCs, WBCs, and platelets)
  • the number of blasts in the blood, bone marrow, or both
  • whether other features like ring sideroblasts or chromosome changes are present

The different types of MDS are:

  • MDS with multilineage dysplasia (MDS-MLD). MDS-MLD is the most common type of MDS. There’s a normal level of blasts. But dysplasia affects two or three blood cell types, and numbers of at least one blood cell type are lower than normal.
  • MDS with single lineage dysplasia (MDS-SLD). There’s still a normal number of blasts. Dysplasia impacts only one blood cell type, and numbers of at least one or two blood cell types are lower than normal.
  • MDS with ring sideroblasts (MDS-RS). Early RBCs have rings of iron called ring sideroblasts inside them. There are two subtypes, based on the amount of dysplasia seen.
  • MDS with excess blasts (MDS-EB). There are high numbers of blasts in the blood, bone marrow, or both. Low levels of one or more blood cell types are also often seen. There are two subtypes based on how many blasts are found. This type is most likely to transform into AML.
  • MDS with isolated del(5q). Cells in the bone marrow have a deletion in their 5th chromosome. Low blood cell levels, often RBCs, and dysplasia are also seen.
  • MDS, unclassifiable (MDS-U). The findings of blood and bone marrow tests don’t align with any of the other five types above.

The WHO also has a separate classification called myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN). These are cancers that have features of both MDS and myeloproliferative neoplasms (MPN). Examples include:

MDS can be difficult to diagnose because they can be hard to distinguish from other conditions that affect the blood and bone marrow.

After getting your medical history and doing a physical examination, a doctor will use the following tests to help diagnose MDS:

  • complete blood count (CBC) with differentialto measure the amounts of different blood cell types
  • peripheral blood smearto assess the appearance of blood cells under a microscope
  • tests of iron, vitamin B12, or folate levels to rule out other causes of anemia
  • bone marrow aspiration and biopsy to provide samples that can be examined to detect abnormalities associated with MDS
  • chromosome tests called cytogenetics to look for chromosomal changes that appear in MDS
  • genetic testing to check for certain genetic changes that happen in MDS

After diagnosis, the doctor will also use a scoring system to help predict your likely outcome, or prognostic score. Some factors that affect the outcome include:

  • the type of MDS you have
  • your blood cell counts
  • the percentage of blasts that are present
  • whether certain genetic or chromosome changes are found
  • the risk of transformation to AML
  • how severe your symptoms are
  • your age and overall health

There are several scoring systems in use. You’ll be classified at some level of low, intermediate, or high risk.

The doctor will make treatment recommendations based on your risk level. Treatment options can include:

  • Watch and wait. This approach is used if you don’t have symptoms and are classified as low or intermediate risk. A doctor will monitor you and provide supportive therapy. They’ll recommend treatment if you develop symptoms or if tests show your condition is progressing.
  • Stem cell transplant (SCT). An SCT from a matched donor, often a sibling, can potentially cure MDS. Ideal candidates for this procedure are young and in overall good health.
  • Drug-based therapy. A variety of drug therapies can be used for MDS, particularly if an SCT isn’t an option. These may include:
    • immunomodulators like lenalidomide (Revlimid), specifically for those with MDS with isolated del(5q)
    • immunosuppressive drugs like cyclosporine and antithymocyte globulin (ATG), which are not approved by the Food and Drug Administration (FDA) for MDS treatment but are prescribed off label in rare circumstances

Supportive therapy is also important for treating MDS. This involves addressing the symptoms of low blood cell counts and includes:

MDS can lead to complications, particularly if it remains untreated. Complications are typically associated with low blood counts and can include:

  • anemia due to low RBC counts
  • frequent or recurring infections, which can be severe due to low WBC counts
  • easy bleeding that can be hard to stop due to low platelet counts

Additionally, MDS can progress to AML in some individuals. According to the ACS, this happens in about 1 in 3 people with MDS.

MDS is a group of cancers where stem cells in the bone marrow don’t develop properly. This leads to an increase in immature cells called blasts that can crowd out healthy blood cells.

The type of MDS you have — along with other factors like symptom severity, certain chromosome or genetic changes, and your age and overall health — all impact your outlook.

MDS can cause serious complications or progress to AML, especially if it’s left untreated. See a doctor for evaluation if you develop symptoms like severe fatigue, shortness of breath, and frequent infections.