What is leukemia? Leukemia is cancer of the blood cells. It starts in the bone marrow, the soft tissue inside most bones. Bone marrow is where blood cells are made. When you are healthy, your bone marrow makes: White blood cells, which help your body fight infection. Red blood cells, which carry oxygen to all parts of your body. Platelets, which help your blood clot. When you have leukemia, the bone marrow starts to make a lot of abnormal white blood cells, called leukemia cells. They don't do the work of normal white blood cells, they grow faster than normal cells, and they don't stop growing when they should. Over time, leukemia cells can crowd out the normal blood cells. This can lead to serious problems such as anemia, bleeding, and infections. Leukemia cells can also spread to the lymph nodes or other organs and cause swelling or pain. Are there different types of leukemia? There are several different types of leukemia. In general, leukemia is grouped by how fast it gets worse and what kind of white blood cell it affects. It may be acute or chronic. Acute leukemia gets worse very fast and may make you feel sick right away. Chronic leukemia gets worse slowly and may not cause symptoms for years. It may be lymphocytic or myelogenous. Lymphocytic (or lymphoblastic) leukemia affects white blood cells called lymphocytes. Myelogenous leukemia affects white blood cells called myelocytes. The four main types of leukemia are: Acute lymphoblastic leukemia, or ALL. Acute myelogenous leukemia, or AML. Chronic lymphocytic leukemia, or CLL. Chronic myelogenous leukemia, or CML. In adults, chronic lymphocytic leukemia (CLL) and acute myelogenous leukemia (AML) are the most common leukemias. In children, the most common leukemia is acute lymphoblastic leukemia (ALL). Childhood leukemias also include acute myelogenous leukemia (AML) and other myeloid leukemias, such as chronic myelogenous leukemia (CML) and juvenile myelomonocytic leukemia (JMML). There are less common leukemias, such as hairy cell leukemia. There are also subtypes of leukemia, such as acute promyelocytic leukemia (a subtype of AML). What causes leukemia? Experts don't know what causes leukemia. But some things are known to increase the risk of some kinds of leukemia. These things are called risk factors. You are more likely to get leukemia if you: Were exposed to large amounts of radiation. Were exposed to certain chemicals at work, such as benzene. Had some types of chemotherapy to treat another cancer. Have Down syndrome or some other genetic problems. Smoke. But most people who have these risk factors don't get leukemia. And most people who get leukemia do not have any known risk factors. What are the symptoms? Symptoms may depend on what type of leukemia you have, but common symptoms include: Fever and night sweats. Headaches. Bruising or bleeding easily. Bone or joint pain. A swollen or painful belly from an enlarged spleen. Swollen lymph nodes in the armpit, neck, or groin. Getting a lot of infections. Feeling very tired or weak. Losing weight and not feeling hungry. How is leukemia diagnosed? To find out if you have leukemia, a doctor will: Ask questions about your past health and symptoms. Do a physical exam. The doctor will look for swollen lymph nodes and check to see if your spleen or liver is enlarged. Order blood tests. Leukemia causes a high level of white blood cells and low levels of other types of blood cells. If your blood tests are not normal, the doctor may want to do a bone marrow biopsy. This test lets the doctor look at cells from inside your bone. This can give key information about what type of leukemia it is so you can get the right treatment. How is it treated? What type of treatment you need will depend on many things, including what kind of leukemia you have, how far along it is, and your age and overall health. If you have acute leukemia, you will need quick treatment to stop the rapid growth of leukemia cells. In many cases, treatment makes acute leukemia go into remission. Some doctors prefer the term "remission" to "cure," because there is a chance the cancer could come back. Chronic leukemia can rarely be cured, but treatment can help control the disease. If you have chronic lymphocytic leukemia, you may not need to be treated until you have symptoms. But chronic myelogenous leukemia will probably be treated right away. Treatments for leukemia include: Chemotherapy, which uses powerful medicines to kill cancer cells. This is the main treatment for most types of leukemia. Radiation treatments. Radiation therapy uses high-dose X-rays to destroy cancer cells and shrink swollen lymph nodes or an enlarged spleen. It may also be used before a stem cell transplant. Stem cell transplant. Stem cells can rebuild your supply of normal blood cells and boost your immune system. Before the transplant, radiation or chemotherapy may be given to destroy cells in the bone marrow and make room for the new stem cells. Or it may be given to weaken your immune system so the new stem cells can get established. Biological therapy. This is the use of special medicines that improve your body's natural defenses against cancer. For some people, clinical trials are a treatment option. Clinical trials are research projects to test new medicines and other treatments. Often people with leukemia take part in these studies. Some treatments for leukemia can cause side effects. Your doctor can tell you what problems are common and help you find ways to manage them. Finding out that you or your child has leukemia can be a terrible shock. It may help to: Learn all you can about the type of leukemia you have and its treatment. This will help you make the best choices and know what to expect. Stay as strong and well as possible. A healthy diet, plenty of rest, and regular exercise can help. Talk to other people or families who have faced this disease. Ask your doctor about support groups in your area. You can also go on the Internet and find stories of people who have leukemia.