What Type of Leukemia Is Most Common in Childhood?

Leukemia is categorized into different types based on whether they are acute (fast-growing) or chronic (slow-growing) and the type of cells in which cancer starts:

• Myeloid leukemia (leukemia starts in myeloid cells)
• Lymphoid leukemia (leukemia starts in lymphoid cells)

Acute leukemias

Acute leukemias progress quickly and require aggressive and immediate treatment. Acute leukemia is further categorized into the following:

• Acute lymphocytic (lymphoblastic) leukemia (ALL): Typically start in early forms of white blood cells (lymphocytes) and accounts for 3 out of 4 childhood leukemias
• Acute myeloid leukemia (AML): Can disrupt normal white blood cells, red blood cells, and platelet production; also called acute myelogenous leukemia, acute myelocytic leukemia, or acute nonlymphocytic leukemia
• Acute undifferentiated leukemias: A rare type of acute leukemia that does not have lymphoid or myeloid cell-specific markers

Chronic leukemias

Chronic leukemias tend to grow slowly and are harder to cure. Chronic leukemias can be further divided into the following:

• Chronic myeloid leukemia (CML): Also called chronic myelogenous leukemia and tends to progress more slowly than acute leukemia
• Chronic lymphocytic leukemia (CLL): Rarely affects children

Juvenile myelomonocytic leukemia (JMML)

JMML is a rare type of leukemia (neither acute nor chronic) that starts in myeloid cells but usually does not grow as fast as AML or as slowly as CML. It is most often found in young children, and the average age at diagnosis is 2 years.

Leukemia typically starts in the bone marrow and can spread to the bloodstream. Certain types of leukemia can spread to other parts of the body, including the lymph nodes, liver, spleen, central nervous system (brain and spinal cord), and testicles.

Unlike other cancers, leukemia does not form tumors or masses. Leukemia generally affects white blood cells (WBCs) and causes rapid uncontrollable growth of WBCs. WBCs are produced by the bone marrow and help prevent infections, acting as the internal defense system of the body. 

However, in people with leukemia, the bone marrow creates an abnormally large number of abnormal white blood cells that do not function correctly and cause serious medical complications.

Some of the known risk factors for childhood leukemia include:

• Family history: Having a sibling with leukemia
• Genetic disorders:
  • Down syndrome (trisomy 21): Children with an extra copy of chromosome 21 are more likely to develop acute lymphocytic (lymphoblastic) leukemia (ALL) or acute myeloid leukemia (AML).
  • Li-Fraumeni syndrome: This is a rare inherited condition caused by a change in the TP53 gene and comes with a higher risk of leukemia.
• Inherited immune system problems:
  • Ataxia-telangiectasia
  • Wiskott-Aldrich syndrome
  • Bloom syndrome
  • Shwachman-Diamond syndrome
• Lifestyle factors: Research studies suggest that excessive alcohol consumption during pregnancy may increase the risk of leukemia in the child.
• Environmental factors: Radiation and certain chemicals can increase the risk of leukemia.
• Exposure to chemotherapy: Children treated with chemotherapy drugs (for other cancers) have a higher risk of developing AML.
• Immune system suppression: Children undergoing intensive treatment to suppress the immune system (for organ transplants) have an increased risk of certain cancers, such as lymphoma and ALL.

Other factors that are controversially linked to childhood leukemia include:

• Exposure to electromagnetic fields
• Living near a nuclear power plant
• Viral infections early in life
• Age of the mother at the time of childbirth
• Fetal exposure to hormones (diethylstilbestrol)
• Paternal smoking history
• Paternal occupational exposure to toxins, chemicals, and solvents
• Chemical contamination of groundwater

A child with leukemia may present with the following symptoms:

• Fatigue
• Weakness
• Feeling cold
• Feeling dizzy or lightheaded
• Shortness of breath or trouble breathing
• Pale skin
• Recurrent infections
• Fever
• Easy bruising and bleeding
• Frequent or severe nosebleeds
• Bleeding gums
• Bone or joint pain
• Abdominal swelling
• Loss of appetite
• Weight loss
• Swollen lymph nodes
• Excessive coughing
• Swelling of the face and arms
• Headaches, seizures, or vomiting (if leukemia spreads to the brain and spinal cord)

Treatment of acute leukemia generally involves the use of chemotherapy and radiation therapy to destroy the leukemia cells:

• Radiation therapy: High-energy X-rays are used to kill cancer cells.
• Chemotherapy: Anticancer medications are administered intravenously (IV) or orally.
• Targeted therapy: Specific drugs are used to target and attack cancer cells without damaging normal cells.
• Stem cell transplants: Healthy stem cells (young blood cells) are transferred into the body.
• Blood transfusion: May be done for low blood counts.
• Antibiotics: May be prescribed to treat any infections.

Potential complications of leukemia may include:

• Serious infections
• Severe bleeding (hemorrhage)
• Blood thickening (due to large numbers of leukemia cells)
• Relapse of the leukemia
• Change to a more aggressive cancer type
• Growth of other cancers
• Heart and lung problems
• Learning problems
• Slow growth and development
• Osteoporosis (thinning of bones)

The prognosis of childhood leukemia depends on certain factors, such as the age at diagnosis, gender, chromosomal changes, type and extent of the disease, and the initial response to treatment.

With early diagnosis and appropriate treatment, the 5-year survival rate of children aged 0-14 years diagnosed with acute lymphocytic leukemia (ALL) has increased to 90%. Children younger than 15 years with acute myeloid leukemia (AML) have a 5-year survival rate of 68%.