Leukemia is cancer of the body's blood-forming tissues, including the bone marrow and the lymphatic system. Many types of leukemia exist. Some forms of leukemia are most common in children. Other forms of leukemia occur mostly in adults. Leukemia usually starts in the white blood cells. Your white blood cells are potent infection fighters — they normally grow and divide in an orderly way, as your body needs them. But in people with leukemia, the bone marrow produces a large number of abnormal white blood cells, which don't function properly. Treatment for leukemia can be complex — depending on the type of leukemia and other factors. But there are strategies and resources that can help to make your treatment successful.

Causes of Leukemia

Scientists don't understand the exact causes of leukemia. It seems to develop from a combination of genetic and environmental factors.

How leukemia forms

In general, leukemia occurs when some blood cells acquire mutations in their DNA — the instructions inside each cell that guide its action. The mutations cause the cell to grow and divide more rapidly and to continue living when normal cells would die. Over time, these abnormal cells can crowd out healthy blood cells, causing the signs and symptoms of leukemia.

How leukemia is classified

Doctors classify leukemia based on its speed of progression and the type of cells involved.

The first type of classification is by how fast the leukemia progresses:

• Acute leukemia. In acute leukemia, the abnormal blood cells are immature blood cells (blasts). They can't carry out their normal work, and they multiply rapidly, so the disease worsens quickly. Acute leukemia requires aggressive, timely treatment.
• Chronic leukemia. This type of leukemia involves more mature blood cells. These blood cells replicate or accumulate more slowly and can function normally for a period of time. Some forms of chronic leukemia initially produce no symptoms and can go unnoticed or undiagnosed for years.

The second type of classification is by type of white blood cell affected:

• Lymphocytic leukemia. This type of leukemia affects the lymphoid cells or lymphocytes, which form lymphoid or lymphatic tissue. Lymphatic tissue makes up your immune system.
• Myelogenous (MI-uh-loj-uh-nus) leukemia. This type of leukemia affects the myeloid cells. Myeloid cells give rise to red blood cells, white blood cells and platelet-producing cells.

Types of leukemia

The major types of leukemia are:

• Acute lymphocytic leukemia (ALL). This is the most common type of leukemia in young children. ALL can also occur in adults.
• Acute myelogenous leukemia (AML). AML is a common type of leukemia. It occurs in children and adults.
• Chronic lymphocytic leukemia (CLL). With CLL, the most common adult leukemia, you may feel well for years without treatment. CLL is very rare in children.
• Chronic myelogenous leukemia (CML). This type of leukemia mainly affects adults. A person with CML may have few or no symptoms for months or years before entering a phase in which the leukemia cells grow more quickly.

Other, rarer types of leukemia exist, including hairy cell leukemia.

Signs & Symptoms of Leukemia

Leukemia symptoms vary, depending on the type of leukemia. Common leukemia signs and symptoms include:

• Fever or chills
• Persistent fatigue, weakness
• Frequent infections
• Losing weight without trying
• Swollen lymph nodes, enlarged liver or spleen
• Easy bleeding or bruising
• Tiny red spots in your skin (petechiae)
• Excessive sweating, especially at night
• Bone pain or tenderness

Diagnosis of Leukemia

Doctors often find chronic leukemia in a routine blood test, before symptoms begin. If this happens, or if you have signs or symptoms that suggest leukemia, you may undergo the following diagnostic exams:

• Physical exam. Your doctor will look for physical signs of leukemia, such as pale skin from anemia and swelling of your lymph nodes, liver and spleen.
• Blood tests. By looking at a sample of your blood, your doctor can determine if you have abnormal levels of white blood cells or platelets — which may suggest leukemia.
• Bone marrow test. Your doctor may recommend a procedure to remove a sample of bone marrow from your hipbone. The bone marrow is removed using a long, thin needle. The sample is sent to a laboratory to look for leukemia cells. Specialized tests of your leukemia cells may reveal certain characteristics that are used to determine your treatment options.

You may undergo additional tests to confirm the diagnosis and to determine the type of leukemia and its extent in your body. Certain types of leukemia are classified into stages, indicating the severity of the disease. Your leukemia's stage helps your doctor determine a treatment plan.

Treatments of Leukemia

Treatment for your leukemia depends on many factors. Your doctor determines your leukemia treatment options based on your age and overall health, the type of leukemia you have, and whether it has spread to other parts of your body.

Common treatments used to fight leukemia include:

• Chemotherapy. Chemotherapy is the major form of treatment for leukemia. This drug treatment uses chemicals to kill leukemia cells. Depending on the type of leukemia you have, you may receive a single drug or a combination of drugs. These drugs may come in a pill form, or they may be injected directly into a vein.
• Biological therapy. Biological therapy works by helping your immune system recognize and attack leukemia cells.
• Targeted therapy. Targeted therapy uses drugs that attack specific vulnerabilities within your cancer cells. For example, the drug imatinib (Gleevec) stops the action of a protein within the leukemia cells of people with chronic myelogenous leukemia. This can help control the disease.
• Radiation therapy. Radiation therapy uses X-rays or other high-energy beams to damage leukemia cells and stop their growth. During radiation therapy, you lie on a table while a large machine moves around you, directing the radiation to precise points on your body. You may receive radiation in one specific area of your body where there is a collection of leukemia cells, or you may receive radiation over your whole body.
• Stem cell transplant. A stem cell transplant is a procedure to replace your diseased bone marrow with healthy bone marrow. Before a stem cell transplant, you receive high doses of chemotherapy or radiation therapy to destroy your diseased bone marrow. Then you receive an infusion of blood-forming stem cells that help to rebuild your bone marrow. You may receive stem cells from a donor, or in some cases you may be able to use your own stem cells. A stem cell transplant is very similar to a bone marrow transplant.

When to seek Medical Advice

• Make an appointment with your doctor if you have any persistent signs or symptoms that worry you.
• Leukemia symptoms are often vague and not specific to the disease. You may overlook early leukemia symptoms because they may resemble symptoms of the flu and other common illnesses.