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Definition
Leukemia is a disorder affecting the production of white blood cells, causing them to reproduce uncontrollably, crowding out existing healthy cells.
These abnormal white cells "overpopulate" the bone marrow, often with immature, nonfunctioning blast cells and spill over into the bloodstream.
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Description
The term leukemia, which is derived from Greek, literally means "white blood." The bone marrow may become severely impaired and unable to maintain production of sufficient levels of red blood cells and platelets. At the same time, white blood cell production becomes so rapid that these cells do not reach the level of maturity necessary to perform their infection-fighting functions.
Leukemic cells infiltrate all the major organs of the body, sometimes causing these organs to malfunction or fail. The kidneys may become impaired. The liver and spleen may become enlarged.
Normally, the spleen acts as a filter for the blood, screening out aging red cells and platelets. When the spleen becomes enlarged, it can actually start doing its job too well, removing perfectly healthy red cells and platelets, further reducing the number of these already scarce cells.
As leukemia progresses, the entire blood system may become flooded with immature blast cells. If this disease is left untreated, a person with leukemia becomes increasingly susceptible to fatigue, excessive bleeding and infections until, finally, the body becomes virtually defenseless, making every minor injury or infection very serious.
Leukemia may be fatal. People may die from internal bleeding which would have been prevented by the platelets. Or, more often, they may die from infections which start with a virus or bacteria that would ordinarily have been wiped out by healthy white blood cells. The exact course leukemia takes, and the speed with which it takes that course, varies with the type and age of the white cells initially affected.
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Types Of Leukemia
There are two major types of leukemia: lymphocytic leukemia, which involves lymphoid-committed cells which form and mature in the lymphatic system, and myelogenous leukemia, which affects myeloid-committed cells that form and mature in the bone marrow. In medical terminology, the root "myelo" always refers to bone marrow.
Each of these types can occur in either the acute or chronic form. The acute form affects young cells still involved in the growth process which divide quickly and hasten the progress of the disease. The chronic form involves more mature cells which have stopped dividing or do so at a relatively slow rate.
Some major examples of leukemia include:
Acute Leukemia. Acute lymphoblastic leukemia (ALL) comprises 80 percent of the acute leukemias of childhood. The peak incidence is between ages 3 and 7. It causes 20 percent of adult acute leukemias. Acute myelogenous leukemia (AML) is chiefly an adult disease with a median age at presentation of 50. Most acute leukemias occur with no clear cause.
Chronic Myelogenous Leukemia. Chronic myelogenous (or granulocytic) leukemia (CML) specifically involves the overproduction of granulocytes which evolve from the myeloid "committed" cell. Since granulocytes are among the most mature white cells produced in the bone marrow, CML is considered to be a slowly-progressing disease. It does progress, however, and if left undiagnosed or untreated will reach its advanced leukemic stage. It is typically a disorder of middle age (median age 42).
Chronic Lymphocytic Leukemia. A common type of leukemia in Western countries is chronic lymphocytic leukemia (CLL), which accounts for 25 to 40 percent of all leukemias. It is a disease of older persons, with 90 percent of cases occurring after age 50 and a median age at presentation of 65.
CLL is defined as a sustained, malignant proliferation of monoclonal, immunologically incompetent lymphocytes, leading to lymphocyte accumulation in the bone marrow, spleen, liver and superficial and deep lymph nodes. Signs and symptoms of the disease often develop so insidiously that the onset cannot be identified. In 25 percent of cases, the disease is discovered on routine clinical examination.
Hairy Cell Leukemia. This is an uncommon form of leukemia that usually strikes middle-aged men. Patients usually suffer from low blood counts of white cells, red cells, and platelets, and most develop recurrent infections.
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Causes and Risk Factors
The cause of leukemia in most circumstances is not known. Some cases appear to be genetic in origin. Others may be related to exposure to toxins, chemicals or drugs, or to radiation.
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Symptoms
Patients may present with fatigue, fever and recurrent infections, weight loss, night sweats, or bleeding.
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Diagnosis
Although suspected by medical history or physical examination, leukemia may be diagnosed incidentally when blood tests or radiological studies are performed for other indications. A bone marrow biopsy may be recommended by your physician.
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Treatment
Leukemia is treated mainly with chemotherapy, although radiotherapy and biological therapy can play a part with some forms of the disease. Bone marrow transplantation may be recommended for some types of leukemia, including acute leukemia and CML.
The goals of therapy are to relieve symptoms and obtain a remission. Remission is the condition in which leukemia is no longer detected and the bone marrow functions normally.
Treatment is usually divided into two phases:
Induction. This is the attempt to attain a remission meaning that the bone marrow appears normal.
Consolidation. This involves giving the same or different treatment, even when the patient appears to be in remission because of the suspected or assumed presence of residual disease that cannot be detected.
Some patients may receive a third phase called maintenance treatment to prolong the remission. Maintenance treatment is more associated with the treatment of ALL (Acute Lymphoblastic Leukemia) than AML (Acute Myelogenous Leukemia).
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Questions to Ask Your Doctor
What are major types of leukemia?
Which type is this?
Is the bone marrow impaired?
What are the principal treatment options?
Do you recommend chemotherapy?
Is radiation therapy of any value in this case?
Will there be a possibility of remission?
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