Introduction

Leukemia, or "white blood," is a cancer of the bone marrow. Bone marrow is actually an organ in the middle of your bones. It produces red blood cells to carry oxygen throughout your body, white blood cells to fight infection, and platelets to prevent bleeding and help blood clot.

The basis of all these cells is a stem cell, also called a "mother cell" or "blast." When you have leukemia, the stem cells no longer function properly. Instead, they become abnormal and are unable to transform into the mature blood cells and platelets needed by the body.

Consequently, patients with leukemia begin experiencing fatigue (because red blood cells can no longer get enough oxygen to tissue, leading to anemia), infections (because you don't have enough normal white blood cells to fight foreign invaders, such as bacteria and viruses), or bleeding (because you don't have enough platelets to help blood clot or the ones you have don't function well enough.) 

Leukemia is not one disease but a set of many, many very different diseases. That's why it's important to ask your doctor which type of leukemia you have and about any chromosomal abnormalities associated with it. This can affect your treatment and prognosis. You should also ask about alternative options you can pursue alongside or in lieu of standard therapy.

Leukemias are identified as "acute" when 20 percent to 30 percent of the white cells in your bone marrow, or blasts are immature, or not fully developed. Leukemia is defined as chronic when less than 5 percent to 10 percent of the blasts are immature.

Below are links to more detailed information about the diagnosis and treatment of the four most common forms of leukemia and on myelodysplastic syndrome (MDS), a condition sometimes referred to as "preleukemia." 

· Acute myeloid leukemia (AML) 
· Acute lymphocytic leukemia (ALL) 
· Chronic myeloid leukemia (CML) 
· Chronic lymphocytic leukemia (CLL)
· Myelodysplastic syndrome (MDS) 

Other, rarer types of leukemia include: acute promyelocytic leukemia (APL),  a form of AML that is treated very differently from AML; and  hairy cell leukemia, related to CLL but with a high cure rate (80 percent to 90 percent) when treated with one or two courses of a drug called chlorodeoxyadenosine. 

Myelodysplastic syndrome (MDS), sometimes called "preleukemia," can in some instances develop into AML. It is marked by overactive stem cells that, nonetheless, don't make enough blood cells.