Leukemia is a cancer of
the blood-forming tissues (hematopoietic tissues: myeloid tissue and lymphoid tissue) of the body, including
the lymphatic system, and bone marrow. The disease results from an excessive production of abnormal white
blood cells in the body. This anarchic excessive number of white blood cells can be immature, acute leukemia;
or mature, chronic leukemia. Leukemia cells cannot fight infection effectively and can interfere with the
production of red blood cells (which carry oxygen) and the platelets (which control
Normally, white blood
cells play an important role in the natural defense system of the body. They attack foreign bodies or
pathogenic entities, such as viruses and bacteria, in order to destroy them and keep the organism healthy.
They are produced in the bone marrow, spongy center of certain bones: hip and thigh bones for instance.
Without healthy, functioning white blood cells, the body may develop serious and sometimes fetal infections.
Generally, leukemia can
be acute or chronic
Acute leukemia occurs
within a few days or weeks, and results in the accumulation of a large number of immature, undeveloped cells
called blasts. These cells cannot function properly like normal white blood cells, which poses a high risk of
infection for people with acute leukemia. Moreover, since the body is engaged in producing blasts, it does
not make enough red blood cells or platelets, which can cause anemia or bleeding disorders.
The two main types of
acute leukemia are acute lymphoblastic leukemia (ALL) and acute myelogenous leukemia (AML).
Chronic leukemia affects
the hematopoietic system and progresses more slowly, over a period of months or years. It is characterized by
the overproduction of mature white blood cells that cannot function normally.
The two main types of
chronic leukemia are chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML).
The most common leukemias
in adults are AML and CLL. There are many different subcategories though.
leukemia (ALL) – this form of blood
cancer is the most common in children. It results from an abnormal reproduction and uncontrolled accumulation
of immature lymphocytes, white blood cells. This causes an abundance of immature lymphocytes in the body
which interfere with the production of red blood cells as well as platelets. For more info, please visit
our acute lymphoblastic
leukemia (ALL) section.
lymphocytic leukemia (CLL) – this
cancer is almost always diagnosed in people over 55 years. This is the most common form of leukemia overall,
and affects about twice as many men as women. CLL progresses slower than the ALL. But without treatment,
gradually, the leukemic cells will outnumber normal cells, including bone marrow where other blood cells are
produced, making survival more difficult. For additional information, please see chronic lymphocytic leukemia
Acute myeloid leukemia
(AML) – this form of leukemia
most commonly affects adults. It is characterized by an uncontrolled growth and accumulation of a type of
immature blood cells found in the bone marrow called myeloblasts. This disorder disrupts the function of red
blood cells, platelets, and normal white blood cells. See acute myeloid leukemia
myeloid leukemia (CML) – this
type occurs more rarely than AML and has less effects on the production of other types of cells. The risks of
suffering from CML are very low in children but increase with age. CML is associated with the Philadelphia
chromosome, a chromosomal disorder resulting from the exchange of portions of genetic material from
chromosomes 9 and 22. See chronic myelogenous leukemia
(CML) for more info.
Dictionary of Scientific & Technical Terms, 6E: hematopoietic tissue
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