Chronic Myelomonocytic Leukemia (CMML)

Chronic myelomonocytic leukemia is a type of blood and bone marrow cancer in which the bone marrow makes too many abnormal blood cells, including monocytes (a type of white blood cell). The monocytes may also have an abnormal shape or size (dysplastic).

Chronic Myelomonocytic Leukemia (CMML)

The Basics

Chronic myelomonocytic leukemia (CMML) starts in the bone marrow and then moves to the blood. It happens when monocytes in the bone marrow begin to grow out of control, filling the bone marrow and preventing other blood cells from growing.

CMML is rare, occurring in about 4 of every 1 million people in the U.S. each year, with about 1,100 new cases diagnosed annually. About 9 out of 10 cases are found in people 60 and older. CMML occurs more often in men than in women and is very rare in young people.

Relation to bone marrow failure diseases:

CMML used to be considered a type of myelodysplastic syndrome (MDS) because patients have abnormal-looking (dysplastic) cells in their bone marrow. But other factors associated with CMML didn't match the definition of MDS. Instead, they more closely resembled myeloproliferative neoplasms, a group of diseases where the bone marrow makes too many cells. Since CMML has features of both myelodysplastic syndrome and myeloproliferative neoplasm, experts created a new “overlap” category of myelodysplastic/myeloproliferative neoplasm.

Between 15 and 30 percent of CMML patients go on to develop acute myeloid leukemia (AML).

Causes

The exact cause of CMML is not known. There are, however, known risk factors that increase the chances of getting CMML. They include:

  • Older age (60 or older)
  • Being male
  • Being exposed to certain chemicals at work or in the environment
  • Being exposed to radiation
  • Past treatment with certain anticancer drugs

Symptoms

The most common sign of chronic myelomonocytic leukemia (CMML) is having too many monocytes, a type of white blood cell, in the blood. These cells can settle in the liver and spleen, causing them to enlarge. They can also cause the bone marrow to make less of other blood cells, resulting in:

  • A low number of red blood cells (anemia) that can lead to feeling very tired, shortness of breath and pale skin
  • A low number of normal white blood cells (leukopenia) that can lead to a fever and frequent or severe infections or, in some cases, a more normal number of white cells but they are ineffective.
  • A low number of blood platelets (thrombocytopenia) that can lead to problems with easy bruising and bleeding, frequent or severe nosebleeds or bleeding from the gums.

Diagnosis

There are a number of tests and tools doctors use to confirm a CMML diagnosis:

  • Physical exam and history
  • Blood tests include:
    • Complete blood count with a differential looks at the total number and type of blood cells in your blood
    • A blood smear allows your doctor to look at your blood under a microscope
    • Blood tests to look for other causes of low blood counts, such as low levels of vitamin b12 and folate
  • Bone marrow aspiration and biopsy to see how your bone monocytes in your bone marrow look (required for diagnosis)
  • Cytogenetic testing looks at abnormalities in your cell DNA may also be done.

Treatment

Treatment of CMML depends on how severe the disease is, as well as the patient’s age and health. Treatment options include:

  • Supportive care with blood transfusions, growth factors and antibiotics to treat symptoms by increasing blood counts and stopping infections
  • Chemotherapy to kill cells cancer cells using cytotoxic agents
  • Radiation therapy with high-energy rays or particles to destroy cancer cells
  • Stem cell transplant, which replaces blood-forming stem cells in your bone marrow with healthy stem cells from a donor

Clinical trials, also called research studies may offer good treatment options for some people with CMML. These studies also help researchers better understand the value of promising new treatments or procedures.