Also Known As
MDS
Myelodysplasia
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This article waslast modified on December 4, 2017.
What is myelodysplastic syndrome?

Myelodysplastic syndrome (MDS) is a group of disorders associated with dysfunctional and ineffective bone marrow that leads to decreased production of one or more types of blood cells. It can lead to anemia, recurrent infections, and/or excessive bruising and bleeding. MDS can arise spontaneously (also known as de novo or primary MDS) or develop after exposure to certain drugs, chemicals, radiation, and toxins (secondary MDS).

According to the American Cancer Society, there are 4-5 new cases of MDS each year for each 100,000 people in the U.S. This is about 13,000 new cases a year. The number is increasing as the population ages. MDS is more common in men than women, and more than 80% of cases occur in people who are older than 60 years.

Normal bone marrow is a fatty fibrous tissue found inside the body's larger bones. It contains stem cells that can differentiate and become one of three types of blood cells as needed. Stem cells commit to becoming a specific type of cell, go through several maturation stages while they develop in the bone marrow, and are then released as mature cells into the blood stream. They may become:

  • Red blood cells (RBCs) – cells that contain hemoglobin and carry oxygen throughout the body
  • White blood cells (WBCs) – five different kinds of cells that fight infections
  • Platelets – special cell fragments that play a vital role in preventing bleeding

With MDS, an abnormal stem cell in the bone marrow begins to clone itself, making replicate copies of one of the cell types. As they replicate, the abnormal cells crowd out other normal bone marrow cells, leading to few normal cells. The cloned cells may be abnormal-looking (dysplastic) under the microscope and do not develop and mature as well as their normal counterparts. Because they are not normal, they may die more quickly and/or be targeted by the body's immune system for destruction. Consequently, the numbers of one or more types of blood cells (RBC, WBC, or platelet) will progressively decrease.

In some cases of MDS, chromosomes of the cloned cells may acquire one or more characteristic changes. Pieces of the genetic material may be deleted, duplicated, and/or translocated (transferred). Many DNA mutations have also been discovered in cases of MDS. These changes can alter the cells' behavior and the affected person's prognosis.

Some people with rare inherited syndromes are at an increased risk of developing MDS. These include Shwachman-Diamond syndrome, Fanconi anemia, dyskeratosis congenita, Diamond-Blackfan syndrome, familial platelet disorders, and familial myelodysplasia. Together, these are called inherited bone marrow failure syndromes.MDS is a group of disorders that can vary greatly. Some cases of MDS "smolder" for many years (so-called low-grade MDS). They may cause few symptoms and may go undiagnosed until significant cell shortages develop and/or until the disease begins to progress quickly. Other cases of MDS are more aggressive and advance rapidly (so-called high-grade MDS). Because of the wide range of types of MDS that exist, there are a few different ways that healthcare practitioners and other professionals classify them in order to better understand, diagnose, manage, and treat the disorders.

Accordion Title
About Myelodysplastic Syndrome (MDS)
  • Types

    Myelodysplastic syndrome (MDS) disorders are described and classified using systems developed by medical researchers and international consensus groups. These systems have evolved over time and include classifications based on the type of cell(s) affected, suspected cause, and outcome (prognosis). Classification of a patient's MDS is intended to aid in predicting the course of disease and making treatment decisions.

    World Health Organization (WHO) Classification
    The current generally-accepted 2016 WHO classification is based upon the appearance of the cells in the blood and bone marrow as well as chromosome analysis (cytogenetics). The following table summarizes the different types:

    MDS Classification Affected Cells* Blasts Comments
    MDS with single lineage dysplasia (MDS-SLD) Low levels of one or two types of circulating blood cells*; significant abnormality in only one type of cell in the bone marrow No or rare blasts (<1%) in blood; no increase in blasts in the marrow (<5%) People with this type generally have a good prognosis. They generally live a long life.
    MDS with ring sideroblasts (MDS-RS) Fifteen percent or more of the immature RBCs in the bone marrow have rings of iron around their nucleus (called ring sideroblasts). If only one type of bone marrow cells appear significantly abnormal, it is called MDS-RS-SLD. If two or all three types of bone marrow cells appear significantly abnormal, it is called MDS-RS-MLD. No or rare blasts (<1%) in blood; no increase in blasts in the marrow (<5%) People with this type also generally have a good prognosis. If a mutation in a gene called SF3B1 is detected, the required number of ring sideroblasts is 5% or higher.
    MDS with multilineage dysplasia (MDS-MLD) Low levels of two or more types of blood cells*; significant abnormality in two or more types of bone marrow cells No or rare blasts (<1%) in blood; no increase in blasts in the marrow blood (<5%) About 10% of people with this type will develop acute leukemia. About half of these patients may die within 2 years of their diagnosis.
    MDS with excess blasts-1 (MDS-EB-1) One or more types of blood cells are low* with or without significant abnormalities among bone marrow cells. Increased number of blasts, but less than 10% in marrow (5-9%) and less than 5% of WBCs in blood (2-4%); no Auer rods About 25% of people with this type will progress to acute myeloid leukemia (AML) and most die within 2 years of their diagnosis.
    MDS with excess blasts-2 (MDS-EB-2) Same as MDS-EB-1 More blasts in the marrow (10-19%) and/or blood (5-19%), or blast number in MDS-EB-1 range but with Auer rods Up to 50% of people with this type develop AML; the remainder of cases are fatal due to bone marrow failure.
    MDS unclassifiable (MDS-U) One or more cell types in blood may be low* with or without significant abnormality among bone marrow cells. No or rare blasts (<1% or exactly 1%) in blood; no increase in blasts in the marrow (<5%) This type is rare. People may have this type when results of their blood and bone marrow tests don't fit into any other MDS category (e.g., MDS with exactly 1% blasts in blood, abnormality in single type of bone marrow cell but all three types of cells are low in blood*, or none of the cell types in blood is low but certain cytogenetic abnormality is detected in bone marrow).
    MDS with isolated del(5q) Low RBCs*, normal WBCs, platelets may be increased No or rare blasts (<1%) in blood; no increase in blasts in the marrow (<5%); no Auer rods Affected cells are missing the long arm of chromosome 5 [called del(5q)] alone or with one additional abnormality except -7 or del(7q). People with this type generally have a good prognosis. Less than 10% progress to acute leukemia. They may respond to Lenalidomide treatment.

    *The thresholds for MDS are hemoglobin <10 g/dL, absolute neutrophil count (ANC) <1,800/microliter, and platelets <100,000/microliter.

    Clinical Classification
    The clinical classification is assigned based upon the perceived cause of the MDS. This includes:

    • Primary (de novo) MDS – when there is not an identifiable cause; the majority of cases of MDS are primary.
    • Secondary MDS – an identifiable cause exists; this may be a previous intensive chemotherapy or an exposure to something that is known to be associated with MDS, such as radiation therapy. This type is less likely to respond to treatment.


    Increased risk for the development of secondary MDS is associated with:

    • Previous chemotherapy for various tumors/cancers
    • Previous high-dose radiation exposure
    • Smoking
    • Exposure to:
      • Herbicides, pesticides and fertilizers
      • Benzene, toluene and other organic chemicals
      • Heavy metals
      • Petroleum industry-related chemicals


    Prognostic Tool
    An International Prognostic Scoring System (IPSS) was developed in 1997 that assigns a low, intermediate, or high prognosis risk value to a person's MDS. The IPSS was revised in 2012 (known as IPSS-R) to incorporate more detailed disease factors (number of blasts, cytogenetics, hemoglobin, absolute neutrophil count, platelet count) and patient's age. The IPSS-R is more precise in predicting outcome than the original IPSS. It assigns a prognosis risk, an estimated median survival time, and a likelihood of progressing to acute myeloid leukemia (AML) within a specified time.

    A World Health Organization (WHO) Prognostic Scoring System (WPSS) has also been developed. It evaluates the type of MDS based on the WHO classification, chromosome abnormalities, and whether or not the patient requires blood transfusions and assigns a prognosis risk.

    Those at a low risk are likely to live longer and are less likely to progress to AML in the next few years, while those at the highest risk are likely to have a poorer prognosis and are more likely to progress to AML within the next few months.

    It is important to note that these tools look at likelihood and cannot determine what will exactly happen with a specific person.

  • Signs and Symptoms

    Signs and symptoms of myelodysplastic syndrome are associated with low blood cell counts. They can vary in severity, from person to person, and over time. Depending on the type of blood cell(s) and the degree to which they are affected, there may be only a few subtle signs and symptoms present, or there may be several and they may overlap categories:

    Low RBC count (anemia)

    • Fatigue
    • Shortness of breath
    • Weakness
    • Pale skin


    Low WBC count (leukopenia)

    • Recurrent infections
    • Fever


    Low platelet count (thrombocytopenia)

    • Excessive bleeding (e.g., nose bleeding)
    • Easy bruising
    • Petechiae (tiny reddish spots on the skin)
  • Tests

    The goals with testing are to diagnose myelodysplastic syndrome (MDS), distinguish it from other conditions that may cause similar symptoms, classify the MDS, evaluate its likely prognosis, monitor it, and guide treatment.

    Primary tests:

    • Complete blood count (CBC) and differential – these are the most frequently ordered tests to help diagnose and monitor MDS. They count the number and proportion of the different types of blood cells and evaluate their size, shape, and maturity. With MDS, they typically reveal low numbers of one or more of the blood cells.

    • Peripheral blood smear – this test evaluates the cells present in the blood. A drop of blood is spread thinly onto a glass slide, then treated with a special stain and examined under a microscope by a trained laboratorian. This test is ordered to help evaluate the immature blast and precursor cells or abnormal-looking (dysplastic) cells that may be present with MDS.
    • Bone marrow aspiration/biopsy – this procedure is used to help diagnose MDS and is sometimes repeated to monitor its progress. A small amount of bone marrow and bone are collected and examined under the microscope by a specialist (pathologist, oncologist, hematologist) to evaluate the number, size, and appearance of various precursor cells present in the marrow.
    • Chromosome analysis (karyotyping) and/or fluorescence in situ hybridization (FISH) – these tests are performed to detect chromosomal abnormalities and to help diagnose and classify MDS, guide treatment, and evaluate prognosis. A more focused version of it may be performed to evaluate those chromosomes and areas that are known to be associated with MDS.


    Sometimes ordered:

    • Flow cytometry – although not needed for MDS diagnosis, the test may be used to help diagnose and classify MDS, especially if the bone marrow blasts appear increased.
    • Immunocytochemistry – a test method that uses antibodies and causes color changes in cells that can be seen under a microscope. This test is not commonly performed for MDS, but it may help distinguish between different types of MDS, leukemia, and other diseases.
    • DNA mutation analysis – If indicated, the tests may be performed to identify certain gene mutations to help classify MDS or predict treatment response or outcome.


    Other testing as needed:

  • Treatment

    Treatment of MDS depends on several factors, including stage of the disease, age and overall health of the individual, as well as prognosis and likely response. At this time, bone marrow stem cell transplants are the only treatment available that will likely cure MDS. They are often the recommended treatment for children and are increasingly being used in adults with MDS also. Without a successful stem cell transplant, MDS is incurable and the focus of treatment is to alleviate symptoms and prevent complications or progression to acute myeloid leukemia. Treatment needs often change over time.

    If anemia is present, then blood transfusions may be necessary. Repeated blood transfusions may lead to the buildup of excess iron in the body and the need for iron chelation therapies. Patients with low blood erythropoietin levels (e.g., <500 IU/L) may benefit from treatment with recombinant erythropoietin, which stimulate red blood cell production.

    Platelet transfusions may be necessary to control excessive bleeding. Drugs that stimulate bone marrow platelet production may also be prescribed (e.g., eltrombopag).

    Antibiotics may be required when white blood cell (WBC) counts are low and a person experiences recurrent infections. Growth factors such as granulocyte colony stimulating factor (G-CSF) and granulocyte macrophage-colony stimulating factor (GM-CSF) may be given to stimulate WBC production.

    Some patients with MDS may be given chemotherapy agents such as 5-Azacitidine and Decitabine, immunomodulating drugs such as Lenalidomide (especially those who have a del(5q) chromosome alteration), or immune suppressants.

    New therapies for MDS continue to emerge from research and clinical trials. Individuals should talk to their healthcare providers about the treatments that are best for their condition.

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Article Sources

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