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Updated on February 26, 2025
Myelodysplastic syndromes (MDS) are a group of bone marrow disorders and blood cancers that disrupt the normal production of blood cells. In medical terminology, “myelo” refers to bone marrow and “dysplastic” refers to the presence of abnormal cells.
When a person has MDS, the bone marrow produces abnormal blood cells that do not mature. The most common manifestation of MDS is anemia, a condition where a person has a low number of red blood cells. Common anemia symptoms include fatigue, dizziness, headaches, pale complexion, chest pain, and/or shortness of breath.
MDS can also cause low levels of white blood cells and platelets, leading to symptoms such as frequent infections and easy bruising/bleeding.
MDS and leukemia
MDS can progress into another type of blood cancer called acute myeloid leukemia (AML). There are also conditions that have features of both MDS and leukemia, such as chronic myelomonocytic leukemia (CMML). These conditions most often affect adults over the age of 65, though they can affect people at younger ages.
MDS and acute myeloid leukemia (AML)
Approximately one-third of people with MDS will develop acute myeloid leukemia (AML), a type of cancer where the bone marrow produces large numbers of immature white blood cells called myeloblasts. AML will reduce the number of red blood cells, platelets, and healthy white blood cells—and cause problems related to low blood counts, such as anemia, bleeding/bruising, and frequent infections.
Some types of leukemia are categorized as chronic, others are acute. Acute leukemias tend to progress quickly. While AML begins in the bone marrow, it spreads into the blood, and can spread to other parts of the body, including the skin, gums, and other organs.
When diagnosed, MDS will be assigned a prognostic score and placed into a lower-risk group or higher-risk group. This will help guide treatment decisions. The likelihood of MDS progressing into AML is an important factor when assigning a risk group and making treatment decisions.
There is debate among medical researchers as to where MDS ends and AML begins. The distinction is typically made based on the number of blast cells—immature blood cells—found in the bone marrow. However, MDS and AML have important genetic and biological differences that affect how their cells behave in the body and respond to treatment.
Chronic myelomonocytic leukemia (CMML)
Chronic myelomonocytic leukemia (CMML) is another type of blood cancer associated with MDS. Previously, CMML was categorized as a type of MDS, but it has been placed in its own category of blood cancers called myelodysplastic/myeloproliferative neoplasms. Myeloproliferative neoplasms are diseases were the bone marrow makes too many blood cells.
People with CMML have lowered numbers of healthy blood cells (as seen in MDS) as well as high numbers of abnormal white blood cells called monocytes. Between 15 and 30 percent of cases of CMML progress to AML.
Your best source of information
Research is ongoing, and knowledge about these conditions, how they are related, and how they can be treated continues to evolve. As a person living with one of these conditions, or a person caring for someone living with one of these conditions, your best source of information will be your healthcare team.
