Juvenile myelomonocytic leukemia (JMML)
- Is an uncommon blood cancer that can progress rapidly without treatment.
- Has features of two other types of blood cancers. For this reason, the World Health Organization (WHO) classifies JMML as a mixed myelodysplastic/myeloproliferative disease.
- Is most commonly diagnosed in infants and children younger than 6 years old.
- Is often diagnosed in infants between ages 3 months and 12 months but rarely diagnosed in newborns.
- Makes up about 1.5 percent of all childhood leukemia cases.
- Is more common in males than females
- Is also called:
- Juvenile chronic myeloid leukemia
- Chronic granulocytic leukemia
- CMML of childhood
- Chronic and subacute myelomonocytic leukemia
- Infantile monosomy 7 syndrome
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What You Should Know
- Many individual factors influence outcomes.
- Hematologists and oncologists are specialists who treat people who have JMML or other types of blood cancer.
What You Should Do
- Talk with your doctor about your child's 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 your child.
How Does JMML Develop?
The DNA (genetic material) of a developing stem cell in the bone marrow is damaged. This is called an “acquired mutation.”
- Stem cells form blood cells (red blood cells, white blood cells and platelets).
The abnormal change(s) affects a white blood cell called a monocyte.
- Normally, monocytes make up about 5 percent to 10 percent of cells in our blood. Monocytes, along with other white cells called neutrophils, are in charge of ingesting and killing microbes (germs) in the blood. When monocytes leave the blood and enter the tissues, they can attack invading organisms and help combat infection and assist other blood cells such as lymphocytes in carrying out their immune function.
- In JMML, monocytes multiply uncontrollably and crowd out normal white blood cells, red blood cells and platelets. Usually these monocytes appear abnormal and not fully mature.
As a result, the number of healthy blood cells (red blood cells, white blood cells and platelets) is usually lower than normal.
- Anemia is a condition when there is a low number of red blood cells in the blood which can cause fatigue and shortness of breath.
- Neutropenia is a condition when there is a low number of neutrophils (a type of white blood cell important in fighting infections).
- Thrombocytopenia is a condition when there is a low number of platelets which can cause bleeding and easy bruising with no apparent cause.
- Low numbers of all three blood cell counts is called pancytopenia.
Doctors don't know why some cells become juvenile myelomonocytic leukemia (JMML) and others don't.
Scientists have established a link between JMML and a rare genetic condition called neurofibromatosis 1. Children with neurofibromatosis are about 500 times more likely to develop JMML or another myeloid disease than are children who don't have the condition.