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.

Tests that examine the blood and bone marrow are used to diagnose myelodysplastic/myeloproliferative neoplasms.

The following tests and procedures may be used:

• Physical exam and health history: An exam of the body to check general signs of health, including checking for signs of disease such as an enlarged spleen and liver. A history of the patient’s health habits and past illnesses and treatments will also be taken.
• Complete blood count (CBC) with differential: A procedure in which a sample of blood is drawn and checked for the following:
  • The number of red blood cells and platelets.
  • The number and type of white blood cells.
  • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
  • The portion of the sample made up of red blood cells.

• Peripheral blood smear: A procedure in which a sample of blood is checked for blast cells, the number and kinds of white blood cells, the number of platelets, and changes in the shape of blood cells.
• Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease.
• Bone marrow aspiration and biopsy: The removal of a small piece of bone and bone marrow by inserting a needle into the hipbone or breastbone. A pathologist views both the bone and bone marrow samples under a microscope to look for abnormal cells.

  The following tests may be done on the sample of tissue that is removed:

  • Cytogenetic analysis: A laboratory test in which the chromosomes of cells in a sample of bone marrow or blood are counted and checked for any changes, such as broken, missing, rearranged, or extra chromosomes. Changes in certain chromosomes may be a sign of cancer. Cytogenetic analysis is used to help diagnose cancer, plan treatment, or find out how well treatment is working. The cancer cells in myelodysplastic/myeloproliferative neoplasms do not contain the Philadelphia chromosome that is present in chronic myelogenous leukemia.
  • Immunocytochemistry: A laboratory test that uses antibodies to check for certain antigens (markers) in a sample of a patient’s bone marrow. The antibodies are usually linked to an enzyme or a fluorescent dye. After the antibodies bind to the antigen in the sample of the patient's bone marrow, the enzyme or dye is activated, and the antigen can then be seen under a microscope. This type of test is used to help diagnose cancer and to tell the difference between myelodysplastic/myeloproliferative neoplasms, leukemia, and other conditions.

KEY POINTS

• There is no standard staging system for myelodysplastic/myeloproliferative neoplasms.

There is no standard staging system for myelodysplastic/myeloproliferative neoplasms.

The process used to find out if cancer has spread is called staging. There is no standard staging system for myelodysplastic/myeloproliferative neoplasms. It is important to know the type of myelodysplastic/myeloproliferative neoplasm in order to plan treatment.

Treatment of juvenile myelomonocytic leukemia (JMML) may include the following:

• Combination chemotherapy.
• Stem cell transplant.
• 13-cis-retinoic acid therapy.
• A clinical trial of a new treatment, such as targeted therapy.

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

The prognosis 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.