Leukemia is cancer of the blood. It begins in the bone marrow, where blood cells are produced. Bone marrow is found in the soft, spongy center of the long bones of the arms and legs. These bones make the three major types of blood cells. White blood cells fight infection. Red blood cells carry oxygen. Platelets make the blood clot and stop bleeding.
In leukemia, there are too many underdeveloped cells in the blood and bone marrow. These crowd out normal, healthy blood cells that the body needs.
Types of Leukemia
There are two major types of leukemia — acute leukemia and chronic leukemia. Almost all children who have leukemia have an acute form. Acute leukemia grows rapidly and worsens quickly if your child does not get treatment. Chronic leukemia develops more slowly.
There are two types of acute leukemia. They are named for the type of blood cell that is cancerous.
Acute lymphocytic leukemia (ALL)
ALL is the most common type of cancer in children. It arises from white blood cells called lymphocytes. Healthy lymphocytes circulate in the lymph system and bloodstream to fight infection. In ALL, these cells do not mature the way they should, so they cannot fight infection well. As a result, children with ALL are more prone to infections.
Acute myelogenous leukemia (AML)
Acute myelogenous leukemia can arise from many types of blood cells that are still developing. All the cells affected by AML start as myeloid stem cells. In a healthy body, some of myeloid stem cells will turn into red blood cells, some into platelets and some into myeloblasts. The myeloblasts go on to become white blood cells called granulocytes.
Chronic leukemia is much less common in children than acute leukemia.
Chronic myelogenous leukemia (CML)
About two to three percent of children with leukemia have chronic myelogenous leukemia. It is like AML except that some blood cells develop and work fine, so the early part of the disease is often less severe. CML in children is treated with chemotherapy given by mouth and, for some patients, a bone marrow (hematopoietic stem cell) transplant.
Other Types of Leukemia
Children can have other kinds of leukemia, too.
Juvenile myelomonocytic leukemia (JMML)
About one to two percent of children with leukemia have juvenile myelomonocytic leukemia. It mainly affects children younger than four years old. JMML is a very hard type of leukemia to treat. The current treatment includes chemotherapy and a bone marrow transplant.
Myelodysplastic syndrome (MDS)
Another disease related to leukemia is called myelodysplastic syndrome, or MDS. In MDS, the child’s bone marrow does not make enough white blood cells, red blood cells and platelets. MDS can range from mild to severe. The best treatment for a person with MDS depends on the type of MDS, age and overall health. Treatment options include managing symptoms with medications, chemotherapy, bone marrow transplant or new drug therapies.
Doctors do not know what causes leukemia in children. There are several factors that may increase a child’s risk. These factors are similar but not identical for ALL and AML. Most children who have leukemia have none of these risk factors.
This list is based on information from the Childhood Acute Lymphoblastic Leukemia PDQ summary and the Childhood Acute Myeloid Leukemia PDQ summary on the National Cancer Institute web site.
Childhood Leukemia Risk Factors
|Sibling who has had leukemia||X||X, especially if they are twins|
|Live in the United States||X|
|Exposed to X-rays before birth||X|
|Exposed to large doses of radiation||X||X|
|Previous treatment with chemotherapy||X||X|
|Certain genetic disorders, including Down syndrome||X||X|
|Exposed to cigarette smoke or alcohol before birth||X|
|Exposed to chemicals such as benzene||X|
|Certain previous disorders of the blood cells||X||X|