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Medically reviewed by Last updated on May 2, 2024.

What is Leukemia?

Harvard Health Publishing

Leukemia is a form of cancer that affects the body’s ability to make healthy blood cells. It starts in the bone marrow, the soft center of various bones. This is where new blood cells are made. Blood cells include

Although cancer can affect red blood cells and platelets, leukemia generally refers to cancer of the white blood cells. The disease usually affects one of the two major types of white blood cells: lymphocytes and granulocytes. These cells circulate throughout the body to help the immune system fight off viruses, infections, and other invading organisms. Leukemias arising from lymphocytes are called lymphocytic leukemias; those from granulocytes are called myeloid, or myelogenous, leukemias.

Leukemia is either acute (comes on suddenly) or chronic (lasts a long time). Also, the type of leukemic cell determines whether it is an acute leukemia or chronic leukemia. Chronic leukemia rarely affects children; acute leukemia affects adults and children.

Leukemia accounts for about 2% of all cancers. Men are more likely to develop the disease than women, and whites are more likely to develop it than people of other racial or ethnic groups. Adults are much more likely to develop leukemia than children. In fact, leukemia occurs most often in elderly people. When the disease occurs in children, it generally happens before age 10.

Leukemia has several possible causes. These include

Leukemia is not believed to be inherited; most cases occur in people without any family history of the disease. However, some forms of leukemia, such as chronic lymphocytic leukemia, occasionally strike close relatives in the same family. But most of the time, no specific cause can be identified.

Acute leukemias
With acute leukemia, immature white blood cells multiply quickly in the bone marrow. Over time, they crowd out healthy cells. (Patients may notice that they bleed a lot or suffer from infections as a result.) When these cells reach high numbers, they can sometimes spread to other organs, causing damage. This is especially true in acute myeloid leukemia. The two main types of acute leukemia involve different types of blood cells:

Both ALL and AML have multiple subtypes. The treatment and prognosis may vary somewhat, depending on the subtype.

Chronic leukemias
Chronic leukemia is when the body produces too many blood cells that are only partially developed. These cells often cannot function like mature blood cells. Chronic leukemia usually develops more slowly and is a less dramatic illness than acute leukemia. There are two main types of chronic leukemia:

Both CLL and CML have subtypes. They also share some characteristics with other forms of leukemia. The treatment and prognosis may vary depending on the subtype.

Rarer forms of leukemia

Lymphatic and myelogenous leukemias are the most common. However, cancers of other types of bone marrow cells can develop. For example, megakaryocytic leukemia arises from megakaryocytes, cells that form platelets. (Platelets help blood to clot.) Another rare form of leukemia is erythroleukemia. It arises from cells that that form red blood cells. Like chronic and acute leukemias, rare forms of the disease can be categorized into subtypes. The subtype depends on what markers the cells carry on their surface.


Early symptoms of leukemia include

Many of these symptoms accompany the flu and other common medical problems. If you have any of these symptoms, see your doctor. He or she can diagnose the problem.


Your doctor may not suspect leukemia based on your symptoms alone. However, during your physical examination, he or she may find that you have swollen lymph nodes or an enlarged liver or spleen. Routine blood tests, especially blood cell counts, may yield abnormal results.

At this point, your doctor may order other tests, including

Genetic tests can help determine exactly what type of leukemia you have. (Each of the four main types has subtypes.) These sophisticated tests may also offer clues as to how you will respond to a particular therapy.

Expected duration

In general, chronic leukemia progresses more slowly than acute leukemia. Without drugs called tyrosine kinase inhibitors or a bone marrow transplant, people with CML can live for several years until the disease acts like AML. Whether tyrosine kinase inhibitors can delay or prevent the transformation of a chronic leukemia to an acute leukemia remains to be seen.


There is no way to prevent most forms of leukemia. In the future, genetic testing may help identify people who are more likely to develop the illness. Until then, close relatives of people with leukemia should have routine physical exams.


The treatment of leukemia is among the most intensive of all cancer therapies. Leukemia is a cancer of the bone marrow. This is the place in the body that manufactures most of the body’s disease fighting cells. The treatment of leukemia wipes out these cells along with the cancer cells.

Treatment often severely compromise immune function and the body’s ability to fight infection. Patients need a tremendous amount of supportive care to recover fully. That’s why people with this disease should be treated in medical centers that routinely care for leukemia patients and that provide excellent supportive care, especially during periods of immune suppression.

Acute leukemias
Unlike other cancers, the treatment of acute leukemia does not depend on how far the disease has advanced but on the person’s condition. Has the person just been diagnosed with the disease? Or has the disease come back after remission (a period when the disease is controlled)?

With ALL, treatment generally occurs in phases. However, not all patients experience all of these phases: 

With AML, treatment generally depends on the patient’s age and overall health. It also depends on the patient’s blood cell counts. As with ALL, treatment usually begins with induction therapy in an effort to send the leukemia into remission. When leukemia cells can no longer be seen, consolidation therapy begins. Bone marrow transplantation may also be considered in the treatment plan.

Chronic leukemias
To treat CLL, your doctor must first determine the extent of the cancer. This is called staging. There are five stages of CLL:

Treatment of CLL depends on the stage of the disease, as well as on the person’s age and overall health. In stage 0, treatment may not be needed, but the person’s health will be monitored closely. In stage I or II, observation (with close monitoring) or chemotherapy is the usual treatment. In Stage III or IV, intensive chemotherapy with one or more drugs is the standard treatment. Some people may need a bone marrow transplant.

For CML, tyrosine kinase inhibitors have become standard therapy, especially for people in the early stage of the disease. Whether a bone marrow transplant is done depends on the stage of the disease, the person’s health, and whether a suitable bone marrow donor is available.

The use of targeted therapies has dramatically changed the prognosis for many people with CML. Patients can live for prolonged periods of time with these medicines. They specifically correct the chemical defects in the cancer cells that had allowed them to grow in an uncontrollable fashion.

Treatment options

The following list of medications are related to or used in the treatment of this condition.

View more treatment options

When To Call a Professional

Call your doctor if you have any symptoms of leukemia. These might include

If you are diagnosed with leukemia, consider transferring your care to a specialized cancer center.


Long term survival of leukemia varies greatly, depending upon multiple factors, including type of leukemia and age of the patient.

Additional Information

The Leukemia and Lymphoma Society

National Cancer Institute (NCI)

American Cancer Society (ACS)

National Heart, Lung, and Blood Institute (NHLBI)


Learn more about Leukemia

Treatment options

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.