Leukemia is a term for cancers of the blood cells. Leukemia starts in blood-forming tissues such as the bone marrow. Your bone marrow makes the cells which will develop into white blood cells, red blood cells, and platelets. Each type of cell has a different job:

• White blood cells help your body fight infection
• Red blood cells deliver oxygen from your lungs to your tissues and organs
• Platelets help form clots to stop bleeding

When you have leukemia, your bone marrow makes large numbers of abnormal cells. This problem most often happens with white blood cells. These abnormal cells build up in your bone marrow and blood. They crowd out the healthy blood cells and make it hard for your cells and blood to do their work.

There are different types of leukemia. Some types are acute (fast growing). They usually get worse quickly if they are not treated. Most childhood leukemias are acute:

• Acute lymphocytic leukemia (ALL), which is the most common type of leukemia in children and the most common cancer in children. In ALL, the bone marrow makes too many lymphocytes, a type of white blood cell.
• Acute myeloid leukemia (AML), which happens when bone marrow makes abnormal myeloblasts (a type of white blood cell), red blood cells, or platelets.

Other types of leukemia are chronic (slow growing). They usually get worse over a longer period of time. They are rare in children:

• Chronic lymphocytic leukemia (CLL), in which the bone marrow makes abnormal lymphocytes (a type of white blood cell). It is more common in teens than children.
• Chronic myeloid leukemia (CML), in which the bone marrow makes abnormal granulocytes (a type of white blood cell). It is very rare in children.

There are some other rare types of leukemia in children, including juvenile myelomonocytic leukemia (JMML).

Leukemia happens when there are changes in the genetic material (DNA) in bone marrow cells. The cause of these genetic changes is unknown. However, there are certain factors that raise the risk of childhood leukemia.

The factors that raise the risk of childhood leukemia include:

• Having a brother or sister, especially a twin, with leukemia
• Past treatment with chemotherapy
• Exposure to radiation, including radiation therapy
• Having certain genetic conditions, such as
  • Ataxia telangiectasia
  • Down syndrome
  • Fanconi anemia
  • Li-Fraumeni syndrome
  • Neurofibromatosis type 1

There are other factors that may raise the risk of getting one or more of the specific types of childhood leukemia.

Some of the symptoms of leukemia may include:

• Feeling tired
• Fever or night sweats
• Easy bruising or bleeding
• Weight loss or loss of appetite
• Petechiae, which are tiny red dots under the skin. They are caused by bleeding.

Other leukemia symptoms can be different from type to type. Chronic leukemia may not cause symptoms at first.

Your health care provider may use many tools to diagnose leukemia:

• A physical exam
• A medical history
• Blood tests, such as a complete blood count (CBC)
• Bone marrow tests. There are two main types - bone marrow aspiration and bone marrow biopsy. Both tests involve removing a sample of bone marrow and bone. The samples are sent to a lab for testing.
• Genetic tests to look for gene and chromosome changes

Once there is a diagnosis of leukemia, other tests may be done to see whether the cancer has spread. These include imaging tests and a lumbar puncture, which is a procedure to collect and test cerebrospinal fluid (CSF).

The treatments for leukemia depend on which type it is, how severe the leukemia is, the child's age, and other factors. Possible treatments might include:

• chemotherapy
• radiation therapy
• Chemotherapy with stem cell transplant
• Targeted therapy, which uses drugs or other substances that attack specific cancer cells with less harm to normal cells

Treatment for childhood leukemia is often successful. But the treatments can cause complications right away or later in life. Children who survived leukemia will need follow-up care the rest of their lives to watch for and treat any complications they may have.

NIH: National Cancer Institute