Juvenile Myelomonocytic Leukemia in Children

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What is leukemia?

Leukemia is blood cancer. It develops in the bone marrow—the soft, spongy center of the long bones that produces the three major blood cells:

  • white blood cells (fight infection)
  • red blood cells (carry oxygen)
  • platelets (help blood clot and stop bleeding)

Normal, healthy cells only reproduce when there is enough space for them to fit, and the body regulates this by sending signals so the cells know when to stop. When your child has leukemia, two things happen:

  1. His bone marrow makes white blood cells that are abnormal.
  2. These abnormal cells do not respond to the signals to stop, and keep reproducing regardless of space available.
  3. The abnormal/immature white cells, called “blasts,” reproduce quickly, and—unlike normal white blood cells—do not help fight infection.
  4. When blasts begin to crowd out the healthy cells in the bone marrow, your child begins to experience symptoms of leukemia (e.g., infections, anemia, bleeding).

What is chronic juvenile myelomonocytic leukemia (JMML)?

JMML is, in some ways, similar to chronic myelogenous leukemia (CML), an uncommon leukemia in children. JMML is a leukemia in which the normal bone marrow production of cells becomes very disregulated. A preponderance of immature monoocytes, a type of white blood cell, is produced in the marrow. The marrow continues to produce these abnormal cells, which crowd out other healthy blood cells.

  • JMML generally cause a more severe disruption in blood counts early in the disease than CML, and is not as responsive to treatment.
  • The symptoms associated with JMML can occur over a period of weeks to months.
  • JMML usually affects children under the age of 2 years. It is a very rare form of childhood leukemia.

Patients with JMML are treated through Dana-Farber/Boston Children's Cancer and Blood Disorders Center, an integrated pediatric hematology and oncology partnership between Dana-Farber Cancer Institute and Boston Children’s Hospital. Visit the Dana-Farber/Boston Children's website for information on our partnership. JMML survivors receive a comprehensive follow-up evaluation from their cancer care team through the David B. Perini, Jr. Quality of Life Clinic at Dana-Farber Cancer Institute.

  • Our childhood cancer survivorship clinic is held weekly.
  • In addition to meeting with your pediatric oncologists, your child may see one of our endocrinologists, cardiologists, neurologists, neuro-psychologists or alternative/complementary therapy specialists.
  • We also offer the following services:
    • patient and family education
    • psychosocial assessment
    • genetic counseling
    • reproductive and fertility evaluation and counseling
    • opportunities to speak with other childhood cancer survivors
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Boston Children's Hospital 300 Longwood Avenue, Boston, MA 02115 617-355-6000 | 800-355-7944