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Myelodysplastic/ Myeloproliferative Neoplasms Treatment (PDQ®)

Patient Version
Last Modified: 06/17/2014

Juvenile Myelomonocytic Leukemia



Juvenile myelomonocytic leukemia is a childhood disease in which too many myelocytes and monocytes (immature white blood cells) are made in the bone marrow.

Juvenile myelomonocytic leukemia (JMML) is a rare childhood cancer that occurs more often in children younger than 2 years. Children who have neurofibromatosis type 1 and males have an increased risk of juvenile myelomonocytic leukemia.

In JMML, the body tells too many blood stem cells to become two types of white blood cells called myelocytes and monocytes. Some of these blood stem cells never become mature white blood cells. These immature white blood cells are called blasts. Over time, the myelocytes, monocytes, and blasts crowd out the red blood cells and platelets in the bone marrow. When this happens, infection, anemia, or easy bleeding may occur.

Signs and symptoms of juvenile myelomonocytic leukemia include fever, weight loss, and feeling very tired.

These and other signs and symptoms may be caused by JMML or by other conditions. Check with your doctor if you have any of the following:

  • Fever for no known reason.
  • Having infections, such as bronchitis or tonsillitis.
  • Feeling very tired.
  • Easy bruising or bleeding.
  • Skin rash.
  • Painless swelling of the lymph nodes in the neck, underarm, stomach, or groin.
  • Pain or a feeling of fullness below the ribs.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis (chance of recovery) and treatment options for JMML depend on the following:

  • The age of the child at diagnosis.
  • The number of platelets in the blood.
  • The amount of a certain type of hemoglobin in red blood cells.