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Juvenile Myelomonocytic Leukemia

National Organization for Rare Disorders, Inc.


It is possible that the main title of the report Juvenile Myelomonocytic Leukemia is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • chronic myelomonocytic leukemia of infancy
  • JMML

Disorder Subdivisions

  • None

General Discussion


Juvenile myelomonocytic leukemia (JMML) is a rare pediatric form of blood cancer. JMML predominately affects young children, most often developing in children under the age of 4. The male/female ratio of affected children is 2-3:1.The disorder is characterized by the uncontrolled growth of an immature form of a specific type of white blood cell known as monocyte precursors. These abnormal cells accumulate in the bone marrow crowding out other healthy cells. The bone marrow produces specialized cells (hematopoietic stem cells) that grow and eventually develop into red blood cells, white blood cells and platelets. These cells are released into the bloodstream to travel throughout the body and perform specific functions. Red blood cells deliver oxygen to the body; white blood cells help the body to fight infection; and platelets allow the body to form clots to stop bleeding. When abnormal cells accumulate in the bone marrow, they can affect the production and function of these healthy blood cells. Abnormal cells can accumulate in other tissues and organs of the body such as the lungs, skin, liver, and intestines. JMML is an aggressive and difficult to treat disease. Currently, the main therapeutic option is allogeneic hematopoietic stem cell transplantation. The exact, underlying cause of JMML is unknown.


Over the years, several different classification systems have been used to define JMML. Currently, the World Health Organization (WHO) classifies JMML as an overlap myelodysplastic syndrome/myeloproliferative disorder because JMML shares characteristics with both of these groups of disorders. Myelodysplastic syndromes are defined as a group of disorders that are characterized by disordered development of blood cells in the bone marrow. Myeloproliferative disorders are defined as a group of disorders characterized by the overproduction (proliferation) of the three main blood cell lines, red or white blood cells or platelets. The first case of JMML was described in the medical literature in 1924.


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World Health Organization (WHO)

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National Bone Marrow Transplant Link

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OncoLink: The University of Pennsylvania Cancer Center Resource

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Children's Leukemia Research Association

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Tel: (516)222-1944

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Rare Cancer Alliance

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For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). A copy of the complete report can be downloaded free from the NORD website for registered users. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational therapies (if available), and references from medical literature. For a full-text version of this topic, go to and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site or email

Last Updated:  5/8/2013

Copyright  2013 National Organization for Rare Disorders, Inc.

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