Acute lymphocytic leukemia (ALL) is a form of leukemia, or cancer of the body’s blood-forming cells. Leukemia is the most common cancer in children and adolescents, accounting for approximately one-third of all cancers in children under the age of 15 and one quarter of all cancers occurring before the age of 20. ALL is the most common form of leukemia in children.

Also known as acute lymphoblastic leukemia, ALL affects the body’s blood making system, including bone marrow and the lymphatic system. ALL develops from lymphoblasts (a type of white blood cell) in the bone marrow. Bone marrow is the soft, inner component of bones. All forms of blood cells are produced in the bone marrow including white blood cells, red blood cells and platelets.

In children with ALL, the bone marrow manufactures a large number of abnormal white blood cells. Over time they can begin to build up, crowding out normal white blood cells, red blood cells and platelets.

ALL develops in the bone marrow but typically spreads quickly into the blood. Eventually it spreads further into the lymph nodes, the liver, the spleen, the brain, the spinal cord and the testicles. Without successful treatment, the disease is usually fatal.

The exact cause of ALL has not been identified. Researchers, however, have gained a greater understanding of how specific changes in DNA can cause cells to develop into leukemia. In most cases of leukemia, the DNA changes are acquired (occurring after birth), rather than inherited. A number of risk factors have also been identified, including age and exposure to high levels of radiation. 

Symptoms of ALL in children vary depending on where it has spread in the body. General signs and symptoms include unexplained weight loss, fever and weakness.

ALL may be first diagnosed in routine blood tests. However, additional tests are typically necessary to examine blood and ibone marrow cells. Diagnostic tests for ALL may include bone marrow tests and  and lumbar puncture. The treatment and prognosis for ALL depends on the subtype of the disease, as well as certain additional factors including the child’s age and white blood cell count at diagnosis. Chemotherapy is the most common treatment method, and children usually respond very well to it.

According to the American Cancer Society (ACS), nearly 2,800 children under age 19 will be diagnosed with ALL in 2007.  This number accounts for about 73 percent of all of the diagnosed cases of childhood leukemia. ALL most often develops in younger children, peaking between 2 and 3 years of age. The disease is more common in children than adults.

The survival rate for children diagnosed with ALL has increased steadily over time due to advances in treatment. The five-year survival rate for children with ALL is now estimated to be 87 percent.