Acute lymphoblastic leukemia (ALL) is a type of cancer that causes the body to produce large numbers of the white blood cells that play an important part in the immune system (lymphocytes). It sometimes is referred to as acute lymphocytic leukemia.

ALL is the most common type of childhood leukemia, usually occurring in children between the ages of 2 and 5 years. It may also occur in adults. ALL is the most successfully treated type of childhood leukemia.

Symptoms of ALL include fever, pale skin, loss of appetite, fatigue, bone pain, and frequent infections.

ALL has several subtypes. A doctor can tell one from another by looking at ALL cancer cells. Each subtype has different proteins on the surface of a cell or different chromosome changes in a cell.

Different subtypes have different treatments. Some subtypes are harder to treat than others. Treatment for ALL may include chemotherapy, radiation, or bone marrow transplant. Children respond better to treatment than adults do.