Leukemia is cancer that begins in in the bone marrow, the organ where blood cells are made. It is a malignant disease of the bone marrow and blood and is characterized by the uncontrolled accumulation of blood cells.
Leukemia that affects lymphoid cells is called lymphocytic leukemia. Leukemia that affects myeloid cells is called myeloid leukemia or myelogenous leukemia.
Chronic Lymphocytic Leukemia and Chronic Myelogenous Leukemia
Chronic leukemia progresses more slowly and allows greater number of more mature, functional cells to be made. Early in the disease, the abnormal blood cells can still do their work, and people with chronic leukemia may not have any symptoms. Slowly, chronic leukemia gets worse. It causes symptoms as the number of leukemia cells in the blood rises.
Both types of leukemia begin in a cell in the bone marrow (the spongy center inside of bones). The cell undergoes a leukemic change and it multiplies into many cells. The leukemia cells grow and survive better than normal cells and, over time, they crowd out normal cells.
Normal stem cells in the marrow form three main cell-types: red cells, platelets and white cells. There are two major types of white cells: germ-ingesting cells (neutrophils and manocytes) and lymphocytes, which are part of the body’s immune system and help fight infection.
The rate at which leukemia progresses and how the cells replace the normal blood and marrow cells are different with each type of leukemia.
- Acute myeloid leukemia (CML): One of the most common types of leukemia among adults, this type of cancer occurs in all age groups, although the average age of onset is age 65. Persons with this type of cancer have abnormal cells inside their bone marrow. The cells grow very fast, and replace healthy blood cells. The bone marrow, which helps the body fight infections, produces cells to carry oxygen and clot the blood, eventually stops working correctly. Persons with AML become more prone to infections and have an increased risk for bleeding as the numbers of healthy blood cells decrease.
- Chronic lymphocytic leukemia (CLL): The leukemia cell that starts the disease makes too many lymphocytes that do not function. These cells replace normal cells in the marrow and lymph nodes. They interfere with the work of normal lymphocytes, which weakens the patient’s immune response. The high number of leukemia cells in the marrow may crowd out normal blood-forming cells and lead to a low red cell count, or anemia. A very high number of leukemia cells building up in the marrow also can lead to low neutrophil and platelet counts. Even higher numbers of cells, however, do not cause blood flow to slow down, unlike CML.
- Adult acute lymphoblastic leukemia (ALL): A fast-growing cancer in which the body produces a large number of immature white blood cells (lymphocytes). In acute leukemia, cancerous cells multiply quickly and replace normal cells. Cancerous cells take over normal parts of bone marrow, causing bone marrow failure. A person with ALL is more likely to bleed and have infections because there are fewer normal blood cells. ALL makes up 80 percent of childhood acute leukemias. Though most cases occur in children ages 3 to 7, the disease may also occur in adults.
Last updated: 5/21/2010 4:20:09 PM