Juvenile Myelomonocytic Leukemia (JMML)

Juvenile Myelomonocytic Leukemia (JMML)

About Leukemia

Leukemia is a type of cancer that affects the body's white blood cells (WBCs).

Normally, WBCs help fight infection and protect the body against disease. But in leukemia, WBCs turn cancerous and multiply when they shouldn't, resulting in too many abnormal WBCs. These cells then interfere with the body's ability to function normally.

Juvenile myelomonocytic leukemia (JMML) is a rare childhood cancer that usually happens in children younger than 2 years old. In JMML, too many myelocytes and monocytes (two types of WBCs) are produced from immature blood stem cells called blasts. These myelocytes, monocytes, and blasts overwhelm the normal cells in the bone marrow and other organs, causing the symptoms of JMML.


The cause of JMML is unknown, but doctors do know that certain medical conditions — such as neurofibromatosis type 1 and Noonan syndrome — can make a child more likely to develop it.

Signs and Symptoms

JMML tends to progress slowly, so at first a child may have few if any symptoms. In fact, symptoms can take months or even years to develop.

The symptoms of all types of leukemia are generally the same and include:


A doctor who suspects a child has leukemia may order tests that include:


Chemotherapy (the use of drugs to kill cancer cells) may be used to temporarily control JMML. However, effective treatment of JMML usually requires a stem cell (bone marrow) transplant.

This procedure involves destroying cancer cells and normal bone marrow and immune system cells with high-dose chemotherapy and then re-introducing healthy donor stem cells into the body. The new stem cells can rebuild a healthy blood supply and immune system.

Even though these therapies are the treatment of choice for kids with JMML, the disease remains difficult to cure. Researchers are looking into the use of alternative treatments, like molecular-targeted therapies (medicines that slow the growth of cancer cells by blocking certain molecules or proteins that help cancer cells grow) and immunotherapies (medicines that mark cancer cells so that the body's immune system can find the cells and remove them from the body).


Being told that your child has cancer can be very frightening, and the stress of treating the disease can be overwhelming for any family.

Although you might feel like it at times, you're not alone. To find support for you or your child, talk to your doctor or a hospital social worker. Many resources can help you get through this difficult time.

Reviewed by: Emi H. Caywood, MD
Date reviewed: June 2015

Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

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OrganizationAmerican Cancer Society The American Cancer Society is the nationwide community-based voluntary health organization dedicated to preventing cancer, saving lives and diminishing suffering from cancer through research, education, advocacy, and service. Call:(800) ACS-2345
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