Myelodysplastic syndromes

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on March 2, 2022.

Myelodysplastic syndromes (MDS) is a complicated-sounding name for a group of cancers that affect blood cells. MDS mostly occur among older adults, rarely developing in people younger than age 50. A little over 10,000 people are affected each year, and they tend to affect men more than women.

There are different types of blood cells. Each performs essential functions in the body.

  • White blood cells fight off infections.
  • Red blood cells transport oxygen throughout the body.
  • Platelets help clot blood to prevent excessive bleeding.

MDS cause a shortage of one or more of these blood cells. Depending on the type of MDS and which blood cells are affected, patients may experience:

MDS are considered a form of cancer, because they cause certain cells to behave abnormally.

In healthy people, new blood cells are created when immature cells, called stem cells, start to change form and mature in the bone marrow (the spongy tissue inside some bones). As these stem cells develop, they become red blood cells, white blood cells or platelets.

In people with MDS, these stem cells do not mature properly. Their bodies are left with too many defective, immature cells and too few essential blood cells. A lack of healthy blood cells leads to issues such as anemia, infections and easy bleeding.

There’s a chance that MDS may progress into a more typical form of cancer called acute myeloid leukemia (AML). About one in three MDS patients develop AML—cancer that starts in bone marrow but quickly spreads.

While most of these patients don’t develop leukemia, the risks of any form of MDS—and the impact it has on the person’s life and well-being—may be substantial. How long a person lives with the disease depends on the type of MDS, as well as age and overall health.

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Diagnosis and types

The type of MDS is determined by examining cells in the blood and bone marrow. Doctors would need blood and bone marrow tests to confirm a diagnosis.

Blood tests may reveal whether the patient’s blood contains low levels of one or more blood cell types, potentially indicating MDS. While blood tests play a role in diagnosing MDS, bone marrow tests are typically needed to confirm the diagnosis.

Bone marrow tests require a bone marrow sample obtained via a syringe or a needle inserted into the hip bone. The sample is analyzed in a laboratory, where the size, shape and quantity of blood cells are examined. The analysis also looks at how many immature blood cells are present—and how few mature blood cells—as these undeveloped cells are a significant indicator of MDS.

Treatments and the risks associated with the disease—such as the possibility that it’ll progress to acute myeloid leukemia—depend on the type of MDS. MDS can be either primary or secondary. 

  • Primary is the most common type. According to the American Society of Clinical Oncology, about 80 percent of MDS patients have primary MDS. This type generally has no obvious risk factors.
  • Secondary MDS is less common and tends to occur as a result of damage to the body’s DNA due to previous radiation or chemotherapy treatment. It may appear several years later (generally between two and 10 years) after the original cancer treatment. 

MDS types are determined based on certain factors related to bone marrow cells—such as how they look under a microscope and what kind of cells (and how many of each) are present.

Below are some common types of MDS, according to the National Cancer Institute (NCI).

Refractory anemia (RA): People with this type of MDS lack red blood cells and have anemia, but their white blood cell and platelet counts are normal. About 20 to 30 percent of MDS patients have this type.

Refractory anemia with ring sideroblasts (RARS): This type of MDS is the same as refractory anemia, except for an excess of iron in the red blood cells. Approximately 10 to 12 percent of MDS patients have this type.

Refractory anemia with excess blasts (RAEB): With this type of MDS, there are too many immature cells in the bone marrow and blood, and the patient has low levels of at least one blood cell type. About 40 percent of people with MDS have this type, and it may progress to AML.

Refractory cytopenia with multilineage dysplasia (RCMD): People with this type of MDS are lacking in at least two types of blood cells. It accounts for about 24 percent of MDS cases and may progress to AML.

Refractory cytopenia with multilineage dysplasia and ringed sideroblasts (RCMD-RS): People with this MDS subtype have anemia and abnormal bone marrow cells. This subtype is very similar to RARS, and it can sometimes turn into AML. 

Myelodysplastic syndrome, unclassified (MDS-U): In this subtype, patients don’t have the specific indicators found in other subtypes, but they do have low numbers of platelets and red and white blood cells. 

MDS associated with isolated del(5q): Patients with this type of MDS have both anemia and missing genetic material from chromosome five. 

Mixed myelodysplastic/myeloproliferative diseases
There are two types of MDS classified as mixed myelodysplastic/myeloproliferative diseases:

  • Chronic myelomonocytic leukemia (CMML)
  • Juvenile myelomonocytic leukemia (JMML) 

These subtypes are caused by changes in the monocyte blood cell, and patients have higher white blood cell counts. While CMML generally occurs in older adults, JMML is found in children  younger than age 6. 

Other rarer types include:
  • Refractory cytopenia with unilineage dysplasia
  • Unclassifiable myelodysplastic syndrome
  • Myelodysplastic syndrome associated with an isolated del(5q) chromosome abnormality
  • Therapy-related myeloid neoplasms
  • Chronic myelomonocytic leukemia


MDS that causes a low red blood cell count and anemia may lead to symptoms such as:

  • Fatigue, dizziness and weakness
  • Shortness of breath
  • Pale skin

MDS that causes a shortage of white blood cell count may cause frequent or severe infections, while MDS that affects platelet levels may cause easy bruising and bleeding, frequent or severe nosebleeds or bleeding from the gums.

Other potential symptoms of MDS include:

  • Weight loss
  • Fever
  • Bone pain
  • Loss of appetite

Often, MDS don’t cause noticeable symptoms in the early stages. Anyone worried about certain symptoms may benefit from a visit to the doctor, who may help determine the cause and the best treatment options. Routine blood tests may detect abnormal blood cell levels and are often the easiest way to catch MDS early.

Causes and risk factors

Scientists have identified several mutations that are common within the bone marrow cells of people with MDS. In most cases, what causes these mutations to develop is unknown.

However, some MDS patients may inherit these mutations from their parents. There are a few genetic syndromes that come with mutations associated with a higher risk of developing MDS, including:

  • Fanconi anemia 
  • Shwachman-Diamond syndrome
  • Diamond Blackfan anemia
  • Familial platelet disorder with a propensity to myeloid malignancy
  • Severe congenital neutropenia 
  • Dyskeratosis congenita

Other people may acquire mutations that increase the risk of MDS through exposures they experience in their lifetime. Certain environmental exposures may promote MDS-causing mutations by damaging the DNA of bone marrow cells, including:

  • Smoking
  • Prior chemotherapy or radiation therapy treatment
  • Long-term exposure to certain chemicals (including pesticides, fertilizers and solvents like benzene) and heavy metals (such as mercury or lead)

Other factors that may increase the chance of developing MDS include:

  • Older age—MDS are much more common in people older than 50, and most people with MDS develop the disease even later (in their 70s or 80s).
  • Gender—For unknown reasons, men are more likely to develop MDS than women.

People cannot change their age or inherited mutations. However, they may be able to lower their risk by avoiding potential environmental causes, such as smoking or high levels of exposure to cancer-causing chemicals and heavy metals.


Your care team will talk to you about the staging of MDS, which is useful in determining prognosis, choosing treatment options, and knowing more about whether or not the MDS may progress to AML. Bone marrow cancers are staged in a slightly different way than other cancers—not based on tumor size or how far the cancer has spread, but on different factors instead.

Several staging systems have been developed over time, which are used to rank MDS cases from very low risk to very high risk. Below are two commonly used staging, or scoring, systems for MDS.

Revised International Prognostic Scoring System (IPSS-R)

Five factors are considered under the IPSS-R system to work out the stage of each primary MDS. They are:

  • Percentage of blast blood cells within the blood marrow
  • Hemoglobin (red blood cell) levels
  • Chromosomal abnormalities
  • Blood platelet levels
  • Neutrophils (type of white blood cell) levels

Note that IPSS-R doesn’t include secondary MDS within its scoring system.

WHO Prognostic Scoring System (WPSS)

The WPSS system stages MDS based on three factors:

  • Specific subtype of MDS
  • Blood transfusions—if and how often a patient needs them
  • Chromosomal abnormalities

Different doctors may use different methods for MDS staging, or a combination of several systems. Always ask your care team if you’re unsure about what staging means for your health and treatment plan.


How MDS are treated may vary depending on the type and severity, as well as on the person's symptoms, overall health and personal preferences.

The goal of treatment is to destroy as much of the disease as possible or slow down its progression. If a more aggressive treatment plan is being considered, doctors may recommend a stem cell transplant, which is the only treatment option known to potentially cure MDS. Stem cell transplants are used in combination with chemotherapy. Chemotherapy helps kill the cancer cells, then a stem cell transplant introduces healthy cells (taken from a donor) into the patient's bone marrow.

Other treatment options may help reduce symptoms, slow the disease's progression and/or avoid complications. These include:

  • Transfusion therapy
  • Blood cell growth factors (drugs that increase the body's production of blood cells)
  • Antibiotics
  • Certain chemotherapy drugs
  • Drugs that weaken the immune system

Clinical trials are also a possible avenue for treatment. Doctors may help patients find and evaluate clinical trial options for MDS. Trials are supported by organizations such as the NCI. Several listing search services are available online, including NCI’s “Steps to Find A Clinical Trial.”


In some patients, MDS can return, even years after the original treatment was completed. This is known as recurrent MDS. If this occurs, it often means some of the malignant cells survived in the body after your treatment.

Your care team will do a full range of testing to learn about the recurrence and recommend treatment options based on the findings. Common recurrent MDS treatments include:

  • Chemotherapy
  • Bone marrow transplantation
  • Palliative care to relieve discomfort and side effects

Clinical trials may also be an option. In a clinical trial, you may have access to newer treatments that are tested along with standard treatments. Ask your care team if a clinical trial is right for you.

Living with any kind of uncertainty is hard. It’s normal to feel worried or shocked to find out MDS has come back, but your care team is there to provide support and resources to help.

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