Leukemia is a type of cancer of the blood and bone marrow; it is a general term used to describe a wide range of conditions, the common feature of which is elevated levels of immature white blood cells. The word leukemia in fact means 'white blood'.
Leukemia has various subtypes, the main distinction being between acute leukemia and chronic leukemia. Acute leukemia involves a rapid increase in the number of immature white blood cells and requires immediate treatment due to the rapid proliferation of malignant cells that spread throughout the body. Chronic leukemia involves excess build up of more mature abnormal white blood cells. It progresses much more slowly than the acute form (months to years), giving doctors time to monitor the disease and decide on the most appropriate treatment.
Within the subtypes of acute or chronic, leukemia is divided into two further subtypes based on the type of blood cell that is affected: lymphocytic or myeloid/myelogenous leukemia.
These subtypes give rise to the four main types of leukemia:
Other, rarer subtypes of leukemia include Hairy Cell Leukemia (HCL), T-cell Prolymphocytic Leukemia (T-PLL), Large Granular Lymphocytic Leukemia, Adult T-cell Leukemia (caused by an HIV-like virus, HTLV), Acute Eosinophilic Leukemia (AEL), Chronic Eosinophilic Leukemia (CEL).
Most (90%) leukemias are diagnosed in adults. For the main subtypes of leukemia:
The cause of leukemia is unknown, but hereditary factors do play a role.
Some industrial chemicals, such as benzene, may be associated with increased risk of leukemia, as can prolonged exposure to X-rays, or other radiation that is used in cancer treatment or CT scans for example. Some medications used in chemotherapy also carry some risk.
Due to leukemia's effect of impairing blood clotting, patients may develop 'pinprick' bleeds, showing up as small (1-2mm) red or purple patches on the skin, caused by broken capillary blood vessels.
See more signs and symptoms listed below.
Diagnosis of leukemia involves examination of the number of red cells, platelets, and different types of white cells in the blood, which can show a harmful imbalance if leukemia is present. In most patients, leukemia produces high numbers of extra white blood cells, many of which are immature or dysfunctional. This can readily be seen under a microscope.
Treatment depends on the type of leukemia present:
To help prevent leukemia, limit exposure to toxic chemicals, as well as to X-rays and other forms of radiation.
Survival rates depend on the type of leukemia:
Acute Eosinophilic Leukemia (AEL) is a rare subtype of acute myeloid leukemia in which most of the cells in the blood and marrow are eosinophilic cells. Chronic Eosinophilic Leukemia (CEL) is a disease in which too many eosinophils are made in the bone marrow.
Loss of appetite and weight loss can occur with AML, CLL or CML.
Due to its effects on white blood cells, leukemia prevents the immune system from working normally, sometimes resulting in frequent infections.
Fevers can occur due to associated bacterial, viral, or fungal infections.
Bone pain, especially in the legs, can be a sign of ALL, CML, or hairy cell leukemia.
Higher numbers of immature white blood cells displace blood platelets, which are essential for the blood clotting process. Increased bruising and bleeding is due to reduced platelets in ALL, AML, and CML.
Seizures can occur due to involvement of the central nervous system in ALL and AML.
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