Leukemia is not just one but several different types and sub-types of blood-related cancers. The disease strikes both adults and children, although certain types are more common in adults than children. Probably the most distinguishing characteristic of leukemia compared to other cancers is that it originates in the bone and can spread to other parts of the body, rather than starting elsewhere in the body and spreading to the bone as can happen with other types of cancer. Following are questions and answers that provide an introduction to leukemia. Visit the new Leukemia section for more extensive leukemia resources.
Leukemia is cancer of the bone marrow (the soft, spongy, inner part of bones where blood cells are made) and blood cells and involves the uncontrolled growth of abnormal blood cells. Leukemia starts in the bone marrow, where it produces large numbers of abnormal blood cells (usually white blood cells) that do not function properly, and can then spread to the lymph nodes, spleen, liver, central nervous system, and other organs.
Yes. Leukemia isn't really one disease; rather, it's a group of four main diseases. The common types of leukemia are categorized according to whether it is acute or chronic and what type of cells are involved (i.e., myelogenous [or myeloid] or lymphocytic). Accordingly, the four major types are:
In other words, lymphocytic leukemia can be either acute or chronic; similarly, myelogenous leukemia can be either acute or chronic, resulting in the four types of leukemia. The terms myelogenous and lymphocytic designate the type of cell involved. Lymphocytic leukemias develop from lymphocytes in the bone marrow. Myelogenous (sometimes referred to as myeloid or myelocytic) leukemia develops from either granulocytes or monocytes, two different types of white blood cells.
Acute leukemia progresses quickly and results in the accumulation of immature, functionless cells in the bone marrow and blood and an inability of the marrow to produce enough normal red and white blood cells and platelets. A deficiency of red blood cells, a condition called anemia, develops in most leukemia patients. The deficiency of normal white blood cells hinders the body's ability to fight infections, while a shortage of platelets results in bruising and easy bleeding. In chronic leukemia, the cells look mature but are actually abnormal. The cells live too long, resulting in a build-up of certain kinds of white blood cells.
Each year, an estimated 27,900 adults and 2,300 children in the U.S. are diagnosed with leukemia. Leukemia is most common among older adults; over half of all leukemia cases are in adults over age 60. The most common types of leukemia among adults are acute myelogenous leukemia (AML) and chronic lymphocytic leukemia (CLL), while the most common type of leukemia among children is acute lymphocytic leukemia (ALL). Incidence rates for all types of leukemia are higher among males than females and higher among whites than African Americans.
Signs and symptoms of leukemia are not exclusive to leukemia; in other words, they may indicate leukemia but they may also indicate some other condition that has similar signs and symptoms. Whether it ends up being leukemia or not, any of the following signs and symptoms of acute leukemia warrant medical attention:
Just because a person has some of the symptoms listed above does not mean that they have leukemia. Blood tests are conducted to confirm whether or not the condition is leukemia. Furthermore, it is possible to have leukemia while lacking any of the signs or symptoms.
The exact cause of leukemia is unknown. However, recently scientists have gained a better understanding of how specific DNA mutations can cause bone marrow stem cells to develop into leukemia. The DNA mutations may result from overexposure to radiation or carcinogenic chemicals but typically leukemia develops without having been exposed to either of these. Another possibility is that a DNA translocation error occurs in a chromosome (i.e., a piece of DNA from one chromosome is essentially swapped for a piece of DNA in another chromosome) and leads to leukemia. Different types of leukemia often have translocations that affect different chromosomes. Tests to find these translocations can be useful in diagnosing leukemia as well as determining if any recurrence of leukemia has occured after treatment.