|
|
Leukemias
Overview
Leukemia is a type of cancer that starts in the blood or in the soft, spongy center of bones called bone marrow. No one knows the exact cause of leukemia, but it develops when immature blood cells, known as stem cells, lose the ability to control their growth. These abnormal cells grow and divide over and over again. They don’t mature or function properly and they may crowd out normal cells, making it hard for them to do their work.
There are two major forms of leukemia: acute and chronic. In acute leukemia, immature white blood cells (called leukocytes) increase quickly, which keeps bone marrow from making normal blood cells. Acute leukemia should be treated right away because these rapidly growing cells quickly become life-threatening.
Chronic leukemia results in a large number of partly mature abnormal white blood cells. It may take months or years for the cancer to progress and many people don’t have symptoms at first. If you have been told that you have chronic leukemia, your doctor may monitor your condition for some time before treating it.
Both chronic and acute forms of leukemia are further grouped by the type of blood cells they affect. Leukemia that begins in lymphoid cells is called lymphoid, lymphocytic or lymphoblastic leukemia, and leukemia that starts in myeloid cells is called myeloid, myelogenous or myeloblastic leukemia.
Some of the main subtypes of leukemia include:
In addition to these main subtypes, a rare type of chronic leukemia, called hairy cell leukemia, affects lymphocytes in bone marrow, blood and the spleen. Under a microscope these cells look like they are covered with tiny hairs.
Risk factors for leukemia
No one knows what causes leukemia, but certain factors can raise your risk:
-
Exposure to high levels of radiation is a risk factor for AML, CML and ALL. Research has shown that people exposed to very high levels of radiation from atomic bomb explosions during World War II have a higher risk for developing leukemia. A more common source of high levels of radiation is radiation therapy, which can also increase your risk.
-
Long-time exposure to high levels of certain chemicals, such as benzene, pesticides, herbicides and formaldehyde, may cause AML, CML or ALL. Cigarette smoke and gasoline contain benzene.
-
Certain chemotherapy agents have been linked with a slightly increased risk for AML or ALL, especially those that contain drugs that interfere with cellular DNA and inhibit cancer cell growth (alkylating agents), or those that block enzymes needed for cells to divide and grow (topoisomerase inhibitors).
-
Some medical conditions can increase the risk for acute leukemia as well. These include Down syndrome and other inherited disorders that involve chromosomal abnormalities as well as certain blood disorders such as myelodysplastic syndrome.
Symptoms of leukemia
Symptoms of leukemia can vary from person to person and depend on the number of leukemia cells in your bloodstream, the type of leukemia and the area of the body where leukemia cells collect. People with chronic leukemia may have no symptoms, and the disease could be found with routine blood tests. However, people with acute leukemia usually feel sick. If the brain is affected, symptoms may include vomiting, confusion, headaches, loss of muscle control or seizures. Leukemia may also affect the digestive tract, heart, lungs, kidneys or testes. Some common symptoms of both acute and chronic leukemia are shown in Table 1.
Table 1. Common symptoms of acute & chronic leukemia
|
Fever, chills or night sweats |
|
Swollen or tender lymph nodes that are not painful |
|
Frequent and recurrent infections |
|
Feeling weak or tired |
|
Easy bruising and bleeding, such as bleeding gums, purple patches on skin or tiny red spots under skin |
|
Unexplained weight loss or loss of appetite |
|
Discomfort or swelling in the abdomen due to a swollen spleen or liver |
|
Bone or joint pain |
Additional Resources
|