Myelodysplastic Syndromes (MDS) Overview

Myelodysplastic syndromes (MDS) are a group of bone marrow diseases that have an increased risk of developing into acute myelogenous leukemia (AML). While these diseases may all have different symptoms and treatments, the one thing that they all have in common is that they affect how much and how well the bone marrow is able to produce healthy blood cells. Approximately 10,000 people develop MDS in the United States each year.​

Other words that are used to describe MDS are preleukemia, hematopoietic dysplasia, subacute myeloid leukemia, oligoblastic leukemia, or smoldering leukemia.

Red blood cells
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How Does MDS Develop?

MDS begins with DNA damage or mutation in a single blood-forming (hematopoietic) stem cell. As a result of this damage, the bone marrow starts to overproduce blood cells and gets packed with immature or “blast” cells.

In MDS, there is also an increase in programmed cell death (apoptosis), which leads to an interesting paradox. While there may be increased production of cells in the marrow, they do not live long enough to be released out into the blood. Therefore, people with MDS will often suffer from anemia (a low red blood cell count,) thrombocytopenia (a low platelet count,) and neutropenia (a low white blood cell count.)

Risk Factors

It's not known what causes the mutations which create myelodysplastic syndromes, and 90% of the time there is no obvious cause of the disease. Some possible risk factors which are associated with an increased include:

  • Age: The median age of diagnosis is 70, although MDS has been seen even in young children.
  • Ionizing radiation: People who have received medication radiation treatments for cancer, as well as exposure to ionizing radiation from atomic bombs and nuclear accidents are at an increased risk.
  • Chemical exposures: Exposure to some organic chemicals, heavy metals, fertilizers, pesticides, and herbicides raises the risk of the disease.
  • Tobacco smoke
  • Diesel exhaust

Is It a Pre Leukemia?

Measurement of the number of blast cells in the marrow indicates how severe the disease is—the more immature cells, the more severe. Once your marrow shows that its population is made up of more than 20% blast cells, the condition is considered to be AML.

About 30% of cases of MDS progress to AML. However, it is important to note that even if this transformation never occurs, the anemia, thrombocytopenia, and neutropenia associated with MDS is still life-threatening.


Not only does an MDS diagnosis encompass several different bone marrow disorders, there are a number of factors within each of these conditions that determine the behavior and prognosis of the disease. As a result, scientists have struggled to come up with a classification system that takes into account all these different variables.

The first of these systems is the French- American- British (FAB) classification. It breaks MDS down into 5 subtypes based on how the bone marrow looks and the results of the patient’s complete blood count (CBC):

  • Refractory anemia (RA)
  • Refractory anemia with ringed sideroblasts (RARS)
  • Refractory anemia with excess blasts (RAEB)
  • Refractory anemia with excess blasts in transformation (RAEB-T)
  • Chronic monomyelocytic leukemia (CMML)

Since the development of the FAB criteria in 1982, scientists have learned more about the genetic abnormalities that lead to MDS and the role that these mutations play in the course of the disease. As a result, in 2001, the World Health Organization (WHO) published some changes to the FAB system. They added some conditions—5q- syndrome, MDS unclassifiable (MDS-U), and refractory cytopenia with multilineage dysplasia (RCMD)—and subdivided others such as RAEB and CMML based on the percentage of blasts in the bone marrow. They also clarified that anything greater than 20% of blasts in the marrow constituted AML, making RAEB-T leukemia as opposed to an MDS.

The third method of classifying MDS is using the International Prognostic Scoring System (IPSS). This system uses three criteria for determining how MDS will progress: the number of cells in the patient’s circulating blood, the number of immature blast cells in the bone marrow, and cytogenetics (the type of genetic abnormalities associated with the MDS).

Based on these factors, IPSS divides patients into four categories which indicate the “risk” of the MDS- low, intermediate-1, intermediate-2, and high. The IPSS provides an improved way to predict outcomes of MDS, determine a prognosis, and plan treatment.

Primary vs. Secondary MDS

In most patients, MDS seems to develop for no known reason, out of the blue. This is called primary or de novo MDS. As in the case of leukemia and other bone marrow disorders, scientists are not exactly sure what causes primary MDS.

Secondary MDS refers to the condition when it follows previous treatment with chemotherapy or radiation therapy.


MDS is diagnosed using the same techniques used to diagnose leukemia.

The first step is to test the patient’s circulating blood for a complete blood count (CBC). This test looks at the number of healthy red blood cells, white blood cells, and platelets in the blood to get a general idea of what is going on in the marrow. In most cases, a person with MDS will show low numbers of red blood cells (anemia), and possibly low platelets (thrombocytopenia) and neutrophils (neutropenia) as well.

If no other cause can be found for the patient to have anemia, doctors will then perform a bone marrow aspirate and biopsy. In a patient with MDS, the marrow will show an abnormal appearance as well as an increased number of immature or “blast” cells. When the cells are examined at a genetic level, they will show mutations or changes to the chromosomes.

Signs and Symptoms

Patients with MDS may experience symptoms of anemia such as:

  • Shortness of breath with little exertion
  • Pale skin
  • Feeling tired
  • Chest pain
  • Dizziness

A few patients will also have signs of neutropenia and thrombocytopenia as well, including bleeding problems and difficulty fighting off infections.

It is important to note that there are many other, less serious conditions that can cause these signs and symptoms. If you are worried about any health concerns you are experiencing, it is always best to discuss them with your doctor or other medical professionals.

Summing It Up

MDS is not one disease, rather a group of conditions that cause changes to how the bone marrow functions.

As science learns more about genetics and the role they play in the development of these kinds of diseases, we are also learning more about factors that determine the course they will take and the potential outcomes. In the future, researchers will be able to use this information to create new and more effective therapies for MDS.

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  1. Ma X. Epidemiology of myelodysplastic syndromesAm J Med. 2012;125(7 Suppl):S2-S5. doi:10.1016/j.amjmed.2012.04.014

  2. Izak M, Bussel JB. Management of thrombocytopeniaF1000Prime Rep. 2014;6:45. doi:10.12703/P6-45

  3. Sperling AS, Gibson CJ, Ebert BL. The genetics of myelodysplastic syndrome: from clonal haematopoiesis to secondary leukaemiaNat Rev Cancer. 2017;17(1):5-19. doi:10.1038/nrc.2016.112

  4. Shimamura A, Alter BP. Pathophysiology and management of inherited bone marrow failure syndromesBlood Rev. 2010;24(3):101-122. doi:10.1016/j.blre.2010.03.002

  5. Matsuo M, Iwanaga M, Kondo H, et al. Clinical features and prognosis of patients with myelodysplastic syndromes who were exposed to atomic bomb radiation in NagasakiCancer Sci. 2016;107(10):1484-1491. doi:10.1111/cas.13025

  6. Nisse C, Lorthois C, Dorp V, Eloy E, Haguenoer JM, Fenaux P. Exposure to occupational and environmental factors in myelodysplastic syndromes. Preliminary results of a case-control study. Leukemia. 1995;9(4):693-699.

  7. DiNardo CD, Garcia-Manero G, Pierce S, et al. Interactions and relevance of blast percentage and treatment strategy among younger and older patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS)Am J Hematol. 2016;91(2):227-232. doi:10.1002/ajh.24252

  8. Jabbour E, Ghanem H, Huang X, et al. Acute myeloid leukemia after myelodysplastic syndrome and failure of therapy with hypomethylating agents: an emerging entity with a poor prognosisClin Lymphoma Myeloma Leuk. 2014;14(2):93-97. doi:10.1016/j.clml.2013.10.013

  9. Nösslinger T, Reisner R, Koller E, et al. Myelodysplastic syndromes, from French-American-British to World Health Organization: comparison of classifications on 431 unselected patients from a single institution. Blood. 2001;98(10):2935-2941. doi:10.1182/blood.v98.10.2935

  10. Walter RB, Othus M, Burnett AK, et al. Significance of FAB subclassification of "acute myeloid leukemia, NOS" in the 2008 WHO classification: analysis of 5848 newly diagnosed patientsBlood. 2013;121(13):2424-2431. doi:10.1182/blood-2012-10-462440

  11. Malcovati L, Hellström-Lindberg E, Bowen D, et al. Diagnosis and treatment of primary myelodysplastic syndromes in adults: recommendations from the European LeukemiaNetBlood. 2013;122(17):2943-2964. doi:10.1182/blood-2013-03-492884

  12. Benton CB, Khan M, Sallman D, et al. Prognosis of patients with intermediate risk IPSS-R myelodysplastic syndrome indicates variable outcomes and need for models beyond IPSS-RAm J Hematol. 2018;93(10):1245-1253. doi:10.1002/ajh.25234

  13. Samiev D, Bhatt VR, Armitage JD, Maness LJ, Akhtari M. A primary care approach to myelodysplastic syndromesKorean J Fam Med. 2014;35(3):111-118. doi:10.4082/kjfm.2014.35.3.111

  14. Toma A, Fenaux P, Dreyfus F, Cordonnier C. Infections in myelodysplastic syndromesHaematologica. 2012;97(10):1459-1470. doi:10.3324/haematol.2012.063420

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