Leukemia is cancer of the body’s blood-forming tissues, including the bone marrow and lymph system. When this condition occurs, bone marrow produces a large number of abnormal white blood cells, in some cases giving the blood a white cast.

Normal white blood cells are potent infection fighters. But in people with leukemia, abnormal white blood cells tend to accumulate, blocking production of normal white blood cells and impairing the ability to fight infection.

Treatment for leukemia is complex. Most patients are treated with chemotherapy. Some also may have radiation therapy, a bone marrow transplant (BMT) or biological therapy. In some cases, surgery to remove the spleen may be part of the treatment plan.

There are four main types of leukemia:

  • Acute Myeloid Leukemia (AML) — Occuring in both adults and children, this type of leukemia is sometimes called acute nonlymphocytic leukemia (ANLL).
  • Acute Lymphoblastic Leukemia (ALL) — This is the most common type of leukemia in young children, but also affects adults, including those who are age 65 and older.
  • Chronic Myeloid Leukemia (CML) — Although this condition occurs mainly in adults, a very small number of children also develop CML.
  • Chronic Lymphocytic Leukemia (CLL) —This condition most often affects adults over the age of 55. While it sometimes occurs in younger adults, it almost never affects children.

All types of leukemia are treatable and most are potentially curable.

Leukemia is grouped by how quickly it develops, as well as the type of blood cells it affects. The different forms of leukemia vary greatly in their nature and seriousness and they are classified as either “acute” or “chronic.”

  • Acute leukemias are more aggressive with severe symptoms and cause major medical problems quickly. Without effective treatment, most patients will die in days to weeks.
  • Chronic leukemias develop at a much slower rate. Some do not require treatment for months or years.

Leukemias also are classified as “myeloid” or “lymphoid.” This refers to the type of white blood cell that has become cancerous. Myeloid cells give rise to neutrophils, an important type of white blood cell that kills bacteria. Lymphoid cells give rise to lymphocytes, which protect against bacterial germs including viruses.

Many people believe leukemia is a disease that only affects children, but roughly 10 times as many adults as children are diagnosed with this cancer. New cases of leukemia number nearly 30,000 annually in North America.

Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is a cancer of lymphocytes that live in the bone marrow, lymph nodes and spleen. ALL accounts for 20 percent of acute leukemia in adults, but is also the most common type of acute leukemia in children.

ALL usually causes illness suddenly, within days or weeks. Most problems are related to the replacement of normal bone marrow and diminished normal blood counts. ALL causes anemia, which leads to:

  • Tiredness
  • Low platelet counts
  • Low white blood cell counts
  • Vulnerability to bruising, bleeding and infections

In addition to these signs of bone marrow failure, ALL sometimes can cause enlarged lymph nodes, an enlarged liver or spleen, or pain in the bones or joints.

Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a cancer of primitive white blood cells in the bone marrow. It is the most common type of acute leukemia seen in adults, accounting for 80 percent of such cases. AML has eight different subtypes that vary in regards to treatment, prognosis and the type of leukemia cell involved.

Typically AML comes on suddenly, within days or weeks. Less often, a patient has been ill for a few months. AML makes people sick primarily by interfering with normal bone marrow function. The leukemia cells replace and crowd out the normal cells of the bone marrow, thereby causing low blood cell counts. This insufficient number of red blood cells results in a condition called anemia, which causes a person to be tired and pale. Lack of platelets can make you more susceptible to bleeding and bruising, especially in the skin, nose and gums.

Lowered levels of normal white blood cells increase the risk of infection. Although infections can be of any type, typical symptoms include:

  • Fever
  • Runny nose
  • Cough
  • Chest pain or shortness of breath
  • Pain with urinating
  • Diarrhea, occasionally

Infections of the bloodstream, called sepsis, and pneumonia are the most dangerous.

Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a disorder in which the lymphocytes lose their normal ability to die and end up accumulating over time. At first, the cells increase only in the blood, but over years they also increase in the lymph nodes, liver, spleen and bone marrow.

Many patients have no symptoms at the time of diagnosis, except for an elevated white blood cell count. Some patients will notice fatigue or enlargement of lymph nodes or fullness in the abdomen due to an enlarged spleen.

When CLL becomes more advanced and begins to replace normal bone marrow, low blood counts can result in anemia and infections. CLL increases a person’s risk of infection because of low production of antibodies (gamma globulins) that help fight bacteria. In 5 percent to 10 percent of cases, CLL causes the destruction of the patient’s own red blood cells and/or platelets through an “autoimmune” process. Destruction of platelets is called immune thrombocytopenic purpura (ITP), and destruction of red blood cells is called autoimmune hemolytic anemia (AHA).

Chronic Myelogenous Leukemia

Chronic myelogenous leukemia (CML) is a chronic leukemia associated with a specific genetic abnormality in the leukemia cell called the Philadelphia chromosome, T9 or 22. This abnormal gene is produced when genetic material called ABL is displaced from chromosome 9 and then replaces the normal part of chromosome 22 next to a region called BCR. The resulting fusion gene BCRABL causes abnormal function of the ABL gene, which leads to the leukemia.

Most patients with CML initially visit their doctor because of:

  • Fatigue
  • Low-grade fevers or sweats
  • Fullness in the abdomen caused by an enlarged spleen

There are three main phases of CML:

  • The disease almost always starts in the chronic phase, during which the disease is usually easy to control with treatment, and patients can lead nearly normal lives.
  • Without a transplant, the disease inevitably progresses over a small number of years into the accelerated phase. When this happens, the blood counts worsen and patients can experience high fever, bone pain and painful enlargement of the spleen.
  • The blast phase of CML is a form of acute leukemia that is very difficult to treat.