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Chronic Myelomonocytic Leukemia

Chronic myelomonocytic leukemia (CMML)

  • Is an uncommon blood cancer that has features of two other types of blood cancers. For this reason, the World Health Organization (WHO) classifies CMML as myelodysplastic/myeloproliferative neoplasms. There are about 1,100 cases each year. 
  • Generally affects older adults.
  • Is diagnosed in twice as many males than females. Has been reported in only a small number of older children and younger adults. 

What You Should Know

  • Many individual factors influence treatment outcomes.
  • Hematologists and oncologists are specialists who treat people who have CMML or other types of blood cancer.

What You Should Do

  • Talk with your doctor about your diagnostic tests and what the results mean.
  • Seek treatment in a cancer center where doctors are experienced in treating patients with leukemia.
  • Ask your doctor whether a clinical trial is a good treatment option for you.

To download lists of suggested questions to ask your healthcare providers, click here.

How Does CMML Develop?

CMML starts when a stem cell in the bone marrow mutates. This results in abnormal blood cell production and an overproduction of blasts and immature monocytes, types of white blood cells that crowd out other blood cells. The blasts never mature completely into normal monocytes so they can’t carry out their normal functions.

Over time, the abnormal monocytes accumulate in the marrow and other organs and interfere with the normal production of other types of blood cells, including red blood cells (which carry oxygen to all the tissues of the body) and platelets (which form clots to help stop bleeding after an injury).

If not treated, CMML can lead to:

  • Low numbers of red blood cells that can no longer supply an adequate amount of oxygen, resulting in anemia.
  • The immune system's inability to guard against infection effectively because of a lack of neutrophils (a type of white cell), a condition called leukopenia.
  • Low numbers of platelets, which can cause bleeding and easy bruising with no apparent cause, a condition called thrombocytopenia.

Risk Factors

Doctors don't know why some cells become chronic myelomonocytic leukemia (CMML) cells and others don't. They've found few risk factors associated with the disease. You can't catch CMML from someone else.

Source: Chronic Myelomonocytic Leukemia (CMML) and Juvenile Myelomonocytic Leukemia (JMML).