Leukemia is a cancer that affects white blood cells. There are many types of leukemia. Each one is named for the kind of white blood cell it affects. These include myelocytes, lymphocytes, plasma cells, and other types of white blood cells.
Leukemia can be acute or chronic. Acute leukemia is a very aggressive leukemia that worsens over a brief period. Two examples of acute leukemia are as follows:
acute lymphocytic leukemia, or ALL
acute non-lymphatic leukemia, or ANLL
Chronic leukemia refers to a leukemia that has a slower course over a much longer period, sometimes years. Two examples of chronic leukemia are as follows:
chronic lymphocytic leukemia, or CLL
chronic myelogenous leukemia, or CML
Certain types of chronic leukemia may eventually develop into a form of acute leukemia.
What is going on in the body?
When the cancerous cells grow in the bone marrow, normal bloods cells are often destroyed or crowded out. Having fewer normal white cells can cause the person to become infected easily. The infections may be serious and life-threatening. Having fewer platelets means that the person may bruise or bleed easily. Anemia, or low numbers of red blood cells, can make the person weak and easily tired.
Eventually, some of the cancerous white cells may leave the bone marrow and enter the bloodstream. They spread through the bloodstream to other parts of the body. This process is known as metastasis.
What are the causes and risks of the disease?
It is not known what causes leukemia. Bone marrow is very sensitive to damage, and some possible causes include:
certain genetic defects
exposure to certain chemicals, such as benzene and toluene
exposure to large doses of radiation
in rare cases, certain types of chemotherapy, which can lead to acute leukemia
some unusual viruses, which can lead to rare types of leukemia