Juvenile myelomonocytic leukemia

How common is leukemia?  Who develops it? 

Leukemia is the most common form of cancer in childhood.

• It affects approximately 3,000 children each year in the US, accounting for about 30 percent of childhood cancers.
• Leukemia can occur at any age, although it is most commonly seen in children between 2 and 6 years of age.
• The disease occurs slightly more frequently in males than in females, and more commonly seen in Caucasian children than in children of other races.

What causes JMML?

In nearly all cases, it is not known what causes leukemia. In the majority of childhood leukemias, gene mutations and chromosome abnormalities in the leukemia cells occur sporadically (by chance). The abnormalities found in leukemia cells are not found in the other cells of the body.

Can damage to the child’s immune system lead to leukemia?

Your child’s immune system plays an important role in protecting his body from diseases, and possibly cancer. This means that an alteration or defect in his immune system may increase the risk for developing leukemia.

Factors such as exposure to certain viruses, environmental factors, chemical exposures and various infections have been associated with damage to the immune system, but none of these factors has been definitively linked as a cause of childhood leukemia.

What are the different types of leukemia?

In addition to JMML, there are three main types of leukemia: acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), and chronic myleogenous leukemia.

How do myelogenous leukemias differ from lymphoblastic leukemia?

A different type of white blood cell is affected.  In myelogenous leukemias (both CML and AML) it’s the granulocyte; in lymphoblastic leukemia (ALL), it’s another kind called a lymphocyte.  In all cases—CML, AML and ALL—the cells become abnormal, reproduce too quickly, ignore orders to stop, and crowd out healthy blood cells. 

What’s the difference between CML and AML?

Acute myelogenous leukemia (AML):

• may be also called granulocytic, myelocytic, myeloblastic, or myeloid leukemia.
• It accounts for about 20 percent of the childhood leukemias.
• With AML, these cells are most commonly found in the bone marrow and blood, but can also appear in the spinal fluid and the skin.
• Rarely, they can form into solid tumors called chloromas.
• The symptoms associated with AML usually occur over a short period of days to weeks.

Chromic myelogenous leukemia (CML):

• Symptoms may come on slowly, over weeks or months.
• CML is often accompanied by a specific type of chromosome rearrangement:
  • Part of chromosome #9 breaks off and attaches itself to chromosome #22.
  • There is an exchange of genetic material between these two chromosomes.
  • This rearrangement changes the position and functions of certain genes, which results in uncontrolled cell growth.

What are the symptoms of JMML?

With JMML, there are usually no symptoms in the early stages. When then do occur, your child may experience symptoms over a period of weeks or months.

Because leukemia is cancer of the blood-forming bone marrow, the initial symptoms are often related to abnormal bone marrow function. The bone marrow is responsible for storing and producing about 95 percent of the body's blood cells, including the red blood cells, white blood cells, and platelets.  While each child may experience symptoms of JMML differently, some of the most common include:

• general fatigue or weakness
• recurrent infections- Although there may be an unusually high number of white blood cells on your child’s blood count, these white blood cells are immature and do not fight infection. Your child may have had several viral or bacterial infections over the past few weeks, and may show symptoms of an infection such as fever, runny nose and cough.
• bone and joint pain– Your child may also experience pain in his bones and joints. This pain is usually a result of the bone marrow being overcrowded and "full."
• abdominal pain– stomach aches may also be a symptom of leukemia. Leukemia cells can collect in your child’s kidney, liver and the spleen, causing enlargement of these organs. Pain in the abdomen may cause your child lose his appetite, and lose weight.  
• swollen lymph nodes- your child may also have swelling in the lymph nodes under the arms, in the groin, chest and in the neck. Leukemia cells may collect in the nodes, causing swelling.

It is important to understand that the symptoms of leukemia may resemble other blood disorders or medical problems. These are common symptoms of the disease, but do not include all possible symptoms. Always consult your child's physician for a diagnosis.