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Page: Four Major Types
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Leukemia is a broad term covering a spectrum of diseases.
Acute vs. Chronic
Leukemia is clinically and pathologically split into its acute and chronic forms.
* Acute leukemia is characterized by the rapid growth of immature blood cells. This crowding makes the bone marrow unable to produce healthy blood cells. Acute forms of leukemia can occur in children and young adults. (In fact, it is a more common cause of death for children in the US than any other type of malignant disease). Immediate treatment is required in acute leukemias due to the rapid progression and accumulation of the malignant cells, which then spill over into the bloodstream and spread to other organs of the body. If left untreated, the patient will die within months or even weeks.
* Chronic leukemia is distinguished by the excessive build up of relatively mature, but still abnormal, blood cells. Typically taking months to years to progress, the cells are produced at a much higher rate than normal cells, resulting in many abnormal white blood cells in the blood. Chronic leukemia mostly occurs in older people, but can theoretically occur in any age group. Whereas acute leukemia must be treated immediately, chronic forms are sometimes monitored for some time before treatment to ensure maximum effectiveness of therapy.
Lymphoid vs. myeloid
Furthermore, the diseases are classified according to the type of abnormal cell found most in the blood.
* When leukemia affects lymphoid cells (lymphocytes and plasma cells), it is called lymphocytic leukemia.
* When myeloid cells (eosinophils, neutrophils, and basophils) are affected, the disease is called myeloid or myelogenous leukemia.
Prevalence of the four major types
Combining these two classifications provides a total of four main categories:
* Acute lymphocytic leukemia (also known as Acute Lymphoblastic Leukemia, or ALL) is the most common type of leukemia in young children. This disease also affects adults, especially those age 65 and older.
* Acute myelogenous leukemia (also known as Acute Myeloid Leukemia, or AML) occurs more commonly in adults than in children. This type of leukemia was previously called acute nonlymphocytic leukemia.
* Chronic lymphocytic leukemia (CLL) most often affects adults over the age of 55. It sometimes occurs in younger adults, but it almost never affects children.
* Chronic myelogenous leukemia (CML) occurs mainly in adults. A very small number of children also develop this disease.
The most common forms in adults are AML and CLL, whereas in children ALL is more prevalent.
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Important notice:
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