Childhood leukemia is the most common form of cancer in children. Leukemia affects roughly 3,800 children each year in the United States and accounts for about 30 percent of childhood cancers. Leukemia is most common in children between ages 2 and 6, but can occur at any age.

Common Types of Leukemia in Children

Leukemia is cancer of the blood. The cancer cells grow in bone marrow — the soft, spongy center of bones — and then enter the blood. Bone marrow produces three main blood cell types.

• White blood cells (leukocytes) fight infections.
• Red blood cells carry oxygen from the lungs around the body.
• Platelets help stop bleeding when the body is injured.

Leukemia happens when the bone marrow makes abnormal cells that don’t mature or work properly. Most often, the abnormal cells are white blood cells, or leukocytes. The abnormal leukocytes overproduce and do not respond to signals telling them to stop growing. These cells do not function normally, and therefore cannot help the body perform needed functions, like fighting infections.

The most common types of childhood leukemia are acute lymphoblastic leukemia (also known as ALL or acute lymphocytic leukemia) and acute myeloid leukemia (also called AML or acute myelogenous leukemia). Both are acute cancers, meaning they grow quickly.

Acute Lymphoblastic Leukemia (ALL)

ALL is the most common type of childhood leukemia, accounting for about 75 percent of childhood leukemia cases. ALL occurs in lymphocytes, which are white blood cells that specialize in recognizing and responding to infections. There are two types of lymphocytes, B cells and T cells, and leukemia can occur in either.

Lymphocytes are a key component of the immune system. They identify and kill or neutralize foreign particles in the body, such as viruses or bacteria. However, in leukemia, the bone marrow produces too many immature lymphocytes (or lymphoblasts) that do not mature properly and thus cannot fight infection. These lymphoblasts then crowd the bone marrow so fewer healthy cells are produced.

Acute Myeloid Leukemia (AML)

AML is the second most common blood cancer in children, and it affects 500 children each year in the United States. AML starts in myeloid cells, which normally form non-lymphocyte white blood cells, red blood cells, or platelets. There are a number of different subtypes of AML, each of which begins in myeloid cells.

There are also other, less common childhood leukemias. These include:

• Hybrid or mixed lineage leukemia — This rare type is a mix of ALL and AML, and it accounts for 2 to 3 percent of all acute leukemias.
• Chronic myeloid leukemia (CML) — CML is rare in children. About 150 children in the United States will be diagnosed with CML each year. CML is chronic, or slower-growing.
• Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) — CLL/SLL is extremely rare in children and also slower-growing. It accounts for about one-third of all leukemias, and it is most common in adults.
• Juvenile myelomonocytic leukemia (JMML) — JMML accounts for 1 to 2 percent of childhood leukemias and primarily impacts children under 4 years old. It is sometimes categorized as a blood disorder instead of cancer.

Causes of Leukemia in Children

Scientists don’t know the exact cause of leukemia in children. Leukemia may be the result of mutations in the genes of bone marrow cells. These mutations are sporadic, meaning they happen by chance and may occur early in the child’s life. In rare circumstances, a child may inherit a condition that increases the risk of leukemia.

Additionally, children who receive chemotherapy or radiation to treat other types of cancer have an increased risk of developing leukemia later in life. Children with certain genetic conditions, such as Down syndrome, are also more likely to develop leukemia.

Unlike in adults, leukemia in children is not strongly associated with environmental or lifestyle risk factors.

There is no way to prevent leukemia in children.

Symptoms of Childhood Leukemia

The signs and symptoms of leukemia in children can vary greatly. Many of the symptoms of leukemia can be caused by other conditions. Nevertheless, if your child has any of these symptoms, it is important for your child to see a doctor so the cause can be determined and treated. Symptoms of leukemia may include:

• Anemia (low red blood cell count) — Red blood cells are needed to carry oxygen throughout the body. With a low red blood cell count, a child may appear tired, pale, cold, or dizzy, and may breathe quickly.
• Recurrent infections or fever — Children with leukemia often have high white blood cell counts, due to a high number of abnormal and dysfunctional white blood cells. Infections may occur because of a shortage of normal, healthy white blood cells.
• Bleeding and bruising — Bleeding and bruising are symptoms of low platelet counts. This is a result of the overcrowding of abnormal cells in the bone marrow, preventing the production of platelets. Children might experience frequent nose bleeds, easy bruising, or petechiae — small red dots on the skin which indicate that small blood vessels have leaked.
• Bone or joint pain — This pain is caused by the overgrowth and crowding of leukemia cells in the bone marrow.
• Abdominal swelling — Leukemia cells can build up in the liver or spleen causing swelling in the abdomen.
• Loss of appetite and weight loss — Swelling in the liver or spleen can compress the stomach and make children feel full quickly, resulting in weight loss.
• Swollen lymph nodes — Lymph nodes are small collections of immune cells in the body, responsible for filtering lymph fluid. Leukemia cells collect in these nodes, causing swelling under the arms, or in the groin, chest, or neck.
• Difficulty breathing — Certain types of leukemia can affect organs in the middle of the chest, such as the lymph nodes or the thymus (a small gland between the lungs). If these organs become enlarged due to the buildup of leukemia cells, they can press on the trachea (windpipe) and make it difficult to breathe.
• Swelling of the face and arms — If the thymus becomes enlarged, it can press on a large vein called the superior vena cava (SVC). This can cause a backup of blood in the veins and swelling in the face, neck, arms, and upper chest. This is known as SVC syndrome. Symptoms of SVC syndrome may also include changes in skin color (bluish or reddened), headaches, dizziness, and changes in consciousness.

In both forms of acute leukemia (ALL or AML), these symptoms can have a sudden onset in a matter of days or weeks. In chronic leukemia (CML), these symptoms may develop slowly over the course of months or years.

The symptoms listed above are common symptoms of leukemia, but do not include all possible symptoms. It is important to note that these symptoms may appear to resemble other medical problems, such as blood disorders.

What to Do If Your Child Has Symptoms of Leukemia

If you notice your child is experiencing symptoms of leukemia, it is essential that they be seen by their pediatrician. It is also important to discuss being referred to a pediatric oncologist, who specializes in treating children with cancer. You may be referred to a pediatric cancer center. These cancer centers offer specialized care and clinical trials run by the Children’s Oncology Group (COG), which is supported by the National Cancer Institute (NCI).

If leukemia is suspected, your child will undergo diagnostic tests. These may include blood tests, bone marrow aspiration, bone marrow biopsy, lumbar puncture (spinal tap), lymph node biopsy, and genetic testing.

Next Steps After Diagnosing Childhood Leukemia

Your child may first receive blood transfusions and antibiotics to restore blood counts and fight infections soon after the diagnosis of leukemia. Treatment will depend on the type of leukemia and other factors. Possible treatments include chemotherapy, radiation therapy, stem cell transplants, targeted therapy, and clinical trials.

It is important to seek emotional support for your child, yourself, and other family members. Speaking with a therapist, attending in-person support groups, or connecting with others on MyLeukemiaTeam can help your entire family face cancer.

You and Your Child Are Not Alone With Childhood Leukemia

On MyLeukemiaTeam, the social network and online support group for those living with leukemia and their caregivers, members talk about a range of personal experiences. A number of members have children with leukemia.

Have you and your family faced childhood leukemia? Share your experience in the comments below or on MyLeukemiaTeam.