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Leukemia
What Is Leukemia
Leukemia is a disease of the blood-producing structures-the bone marrow and the lymphatic system (the spleen, liver, and lymph nodes)-in which a large number of abnormal white blood cells are produced. These malignant cells are released into the blood, where they circulate throughout the body and may infiltrate other body tissues, including the liver, the skin, and the central nervous system.
Blood contains three broad types of cells: Red cells carry oxygen; platelets are crucial for clotting; white cells fight infections and are part of the body's immune system. White cells are further subdivided into two major types. Cells from the myeloid lineage destroy bacteria and other foreign invaders by engulfing them; cells from the lymphoid lineage produce antibodies that bind to infectious agents and help in their elimination. Immature white cells, known as blasts, are produced by the bone marrow and lymphatic system but are not released into the bloodstream until they mature. Normally, the body produces only enough white cells to replace the ones that have died. However, in leukemia, too many blasts and mature white cells are produced. Excessive numbers of white cells in the bone marrow interfere with the production of other types of blood cells. The resulting lack of red cells starves body tissues of oxygen; deficiency of platelets greatly increases the risk of bleeding; lack of certain white cells can compromise the immune system.
The different types of leukemia are classified as acute and chronic, according to how quickly the disease tends to progress, and by the type of white cell affected. The acute leukemias are rapidly progressing diseases, usually requiring immediate treatment. The chronic leukemias have two phases, gradual and acute. During the gradual phase, which may last for years, symptoms often do not occur, and treatment may be unnecessary; however, the symptoms and rapid progress of the acute phase of chronic leukemia resemble those of the acute leukemias.
Leukemias are further distinguished by the type of white cell affected: acute and chronic myelogenous leukemia (AML and CML) and monocytic leukemia involve the myeloid family of cells; acute and chronic lymphocytic leukemia (ALL and CLL) and hairy cell leukemia involve the lymphoid family of cells. Hairy cell leukemia is a rare chronic leukemia marked by the production of abnormal lymphocytes with irregular hairlike protrusions.
Overall, leukemias account for about 5 percent of cancers in the United States. Half of the cases of leukemia are the acute leukemias; ALL is the most common cancer in children, while over 80 percent of cases of AML occur in adults. Of the chronic leukemias, CLL is the most common overall, comprising over one-third of cases in the United States, and CML accounts for one-fifth of cases. Despite leukemia's reputation as a childhood disease, it mainly affects people over 60, especially men. Treatment can bring about remission, although relapse is common. In children, the treatment of acute lymphocytic leukemia is a modern success story: 50 to 70 percent achieve long-term remission and are considered cured.
Symptoms of Leukemia
- No symptoms associated with the early stages
of the chronic leukemias.
- General feeling of poor health (ALL, AML,
CLL, CML, hairy cell leukemia).
- Fever and night sweats due to associated bacterial,
viral, or fungal infections. Infections
may be frequent because of the weakened
immune system and the absence of enough
white cells for proper defense (ALL, AML,
CLL, CML, hairy cell leukemia).
- Severe fatigue, pallor, and breathing difficulty,
due to anemia (ALL, AML, CLL, CML).
- Headaches and seizures due to involvement of
the central nervous system (ALL, AML).
- Increased bruising and bleeding due to
reduced platelets (ALL, AML, CML).
- Bone pain, especially in the legs (ALL, CML,
hairy cell leukemia).
- Abdominal pain, nausea, and abdominal distention
due to enlargement of the spleen
(ALL, CML, hairy cell leukemia).
- Loss of appetite and weight loss (AML, CLL,
CML).
- Swollen glands due to enlarged lymph nodes
(CLL) and spleen (CML).
- Joint pain due to gout (CML)
What Causes Leukemia
- The cause of leukemia is unknown.
- Hereditary factors play a role. A genetic abnormality known as the Philadelphia chromosome leads to CML; 10 percent of people with ALL have also been shown to have the Philadelphia chromosome.
- Some industrial chemicals, such as benzene, may be associated with leukemia.
- Prolonged exposure to x-rays or radiation (as used in cancer treatment) may lead to leukemia.
- Some medications used in chemotherapy, such as the alkylating agents mechlorethamine, chlorambucil, cyclophosphamide, and busulfan, may carry a higher risk of leukemia.
- Adult T-cell leukemia, a rare type of leukemia, is caused by the human T-cell leukemia virus. However, not everyone infected with the virus develops leukemia.
Prevention of Leukemia
- Limit exposure to toxic chemicals, as well as to x-rays and other forms of radiation, to reduce the risk of ALL, AML, and CML.
Diagnosis of Leukemia
- Examination of the number of red cells, platelets, and different types of white cells in the blood.
- Bone marrow aspiration or biopsy. A sample of bone marrow is usually taken from the hip bone.
- Cytological (cell) studies are performed to determine the presence of the Philadelphia chromosome and to look for other chromosomal abnormalities.
How To Treat Leukemia
- Chemotherapy is used to treat the acute leukemias and the acute phases of the chronic leukemias. High doses are used to induce remission, and in the case of ALL, lower maintenance doses may be continued for months or years to prevent relapses. Bone marrow from the patient may be extracted during a remission and preserved in a frozen state. Removal protects the bone marrow from damage during treatment of a relapse with high doses of chemotherapeutic drugs, after which the preserved marrow cells are given back to the patient.
- Radiation therapy may be used to destroy leukemia cells in the cerebrospinal fluid, central nervous system, spleen, and lymph nodes (ALL, CLL, CML).
- Corticosteroids, usually prednisone, may be prescribed prior to or in addition to chemotherapy (ALL, CLL, the acute phase of CML).
- Bone marrow transplantation may be used to treat and possibly cure ALL, AML, and CML if a compatible donor can be found. The best results occur with a sibling donor. If that is not possible, a search to find a compatible donor may be done through the National Bone Marrow Registry. Before transplant the patient is given intensive chemotherapy alone or along with total body radiation to destroy leukemia cells. Bone marrow may also be extracted from the patient, treated to remove leukemia cells, and then returned after chemotherapy or a combination of chemotherapy and radiation.
- Interferon has been highly successful in the treatment of hairy cell leukemia, with more than 90 percent of patients expected to survive more than five years. Interferon may also be used to treat CML.
- Surgery to remove an enlarged spleen, one of the sites of white cell production, may be necessary in hairy cell leukemia and CLL.
- For all forms of leukemia, transfusions of red blood cells or platelets may be used during treatment to maintain adequate levels of blood components.
- Analgesics may be prescribed for all forms.
- Antibiotics or antifungal medications may be needed to treat associated infections in all forms of leukemia. Common infections are dangerous for the leukemia patient, because both the cancer and its treatment suppress the body's immune system.
When To Call A Doctor
- Call a doctor if you notice an increased tendency to bruise or bleed, or develop severe fatigue, breathing difficulty, bone pain, appetite or weight loss, abdominal pain, swollen glands, or fever.
- Call a doctor if your child develops bone pain, an increased tendency to bruise or bleed, fever, or severe fatigue.
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