Leukemia

Leukemia begins when a single bone marrow cell fails to mature into a blood cell and becomes a leukemia cell. The leukemia cells multiply and eventually fill the bone marrow, crowding out the normal blood-forming cells. This makes it hard for normal cells to do their work of fighting infection, carrying oxygen and stopping bleeding.

As the abnormal cells circulate in the blood, leukemia can spread to other parts of the body such as the lymph nodes, spleen, liver and central nervous system, which includes the brain and spinal cord.

The exact cause of leukemia is not known. The majority of childhood leukemias are acquired diseases. This means that leukemia occurs by chance and is not inherited from a parent. Usually, children with leukemia do not have any known risk factors. Possible risk factors for leukemia include:

• Inherited immune system deficiencies
• Immunosuppressant medicines, such as those provided after organ transplant
• Down syndrome, a genetic condition affecting a child's physical and mental development
• Li-Fraumeni syndrome, a rare genetic condition that greatly increases the risk for cancer

Although every child experiences symptoms differently, the initial symptoms of leukemia are often related to irregular bone marrow function. Symptoms may seem to occur suddenly, developing in a matter of days or weeks. Some symptoms result from too many leukemia cells. Other symptoms result from leukemia cells crowding out normal cells.

Symptoms of leukemia include:

• Pain deep in the bones
• Swollen lymph nodes
• Difficulty breathing
• Broken bones
• Anemia
• Bleeding
• Bruising
• Recurrent infections

Because symptoms of leukemia may resemble other blood disorders or medical problems, it is important to visit your child's primary care doctor if he or she is experiencing any of these symptoms.

The three types of leukemia that affect children most often are:

• Acute lymphoblastic leukemia (ALL). ALL is the most common type of leukemia in young children. "Acute" means the cells become cancerous in the early stage of development. Normal white blood cells fight infection. Lymphoblasts (cancer cells) do not mature correctly and cannot help fight infection. They crowd out other blood cells. The risk for developing ALL is highest in children younger than 5 years of age, but children of all ages and adults can develop ALL. Children respond better to treatment than adults with this type of leukemia.
• Acute myeloid leukemia (AML). AML is the second most common type of childhood leukemia. Normal myeloid cells develop into red blood cells, platelets or white blood cells. Acute myeloid leukemia affects the myeloid cells during early development. Although the abnormal cells are different in ALL and AML, the way in which cancerous cells crowd out healthy cells is similar.
• Chronic myeloid leukemia (CML). CML progresses slowly and is uncommon in children. “Chronic” means cells become cancerous later in development than cells in AML. CML cancerous cells in the marrow do not mature correctly and eventually crowd out healthy cells, similar to the way AML cells do. Almost all CML patients have a specific chromosome defect in the leukemia cells called the Philadelphia chromosome. It causes the uncontrolled growth of the leukemia cells.

Diagnosis of Leukemia

Pediatric cancer doctors at Riley at IU Health start with a complete medical history and physical examination of your child. The most common diagnostic tests for leukemia involve looking at samples of blood and bone marrow under a microscope. Further genetic and immunologic tests determine whether the cells are myeloid or lymphoid, which determines the type of leukemia.

Children with leukemia often require a spinal tap to test for leukemia around the brain and spine. This test looks for cancer cells in the cerebrospinal fluid (the liquid around the brain and spine).