Leukemia is cancer of the blood cells. When someone has leukemia, the body makes large numbers of abnormal blood cells. Leukemia comprises a group of diseases that includes four major types:
- Acute lymphocytic leukemia (ALL) (a childhood disease).
- Acute myeloid
- Chronic myeloid
- Chronic lymphocytic leukemia (CLL) (primarily adult diseases)
Although sometimes thought of as a children's disease, leukemia most frequently occurs in people over the age of 65.
Acute lymphocytic leukemia (ALL) also called acute lymphoblastic leukemia) accounts for about 3 out of 4 cases of childhood leukemia. ALL occurs most commonly in early childhood, peaking between 2 and 4 years of age. This leukemia starts from the lymphoid cells in the bone marrow and then spreads to the blood. From there it can go to the lymph nodes, spleen, liver, central nervous system, and other organs.
Acute myeloid leukemia (AML) goes by many names, including acute myelocytic leukemia, acute myelogenous leukemia, acute granulocytic leukemia, and acute non-lymphocytic leukemia. "Acute" means that the leukemia can progress quickly, and if not treated, would probably be fatal in a few months. AML is a cancer that starts within the bone marrow, in the cells that are supposed to mature into different types of blood cells. In most cases it quickly moves from the bone marrow into the blood. Both children and adults can get AML. Cases of AML in children are spread out across the childhood years, but is slightly more common during the first 2 years of life and during the teenage years.
Chronic lymphocytic leukemia (CLL) is a type of cancer that starts in the white blood cells (lymphocytes) in the bone marrow (the soft inner part of the bones, where new blood cells are made), and then invades the blood. Leukemia cells tend to build up in the body over time. In many cases people have no symptoms for at least a few years. Compared with other types of leukemia, CLL usually grows slowly.
Exposure and Risk
As with most cancers, the cause of most leukemias is unknown. Generally, some risk factors include:
- Chemotherapy drugs known as alkylating agents
- Genetic abnormalities, including Down Syndrome
- Iionizing radiation, high doses
- Long-term benzene exposure
- Rare viruses
The relevance of these factors may depend on the type of leukemia. Moreover, adult leukemia risk factors differ from those of children. For adult-onset leukemia, the most firmly established environmental risk factor is exposure to ionizing radiation; benzene, agricultural exposures, and smoking also have been linked to elevated risk. For acute lymphocytic leukemia in children, their exposure to ionizing radiation and a parent's exposure to pesticides and other chemicals may increase risk.
Leukemia and the Environment
Additional research is needed to better understand the relationship between leukemias and the environment. Research has shown that exposure to high levels of ionizing radiation has been linked to specific types of leukemia in both adults and children.
Reduce Your Risk
Not smoking can reduce the risk for acute myeloid leukemia. Avoiding unnecessary radiation exposure can prevent many types of cancer. Avoiding prolonged exposure to benzene can also reduce risk.