LEUKAEMIA
DESCRIPTION |
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Leukaemia is cancer of the
white blood cells. Blood cells are produced in the bone marrow from
cells called stem cells or blast cells. Bone marrow is found in the
long bones of the limbs (although the amount decreases with age), in
the skull, vertebrae, pelvis and chest bone (sternum).
Production of blood cells
Blast cells differentiate (mature and become specialised) to form
the different types of blood cells, i.e. red blood cells, white
blood cells and platelets. Mature cells are then released into the
circulation.
Red blood cells
carry oxygen around the body to all the organs and tissues. White
blood cells fight infection. There are several types of white blood
cell including:
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Granulocytes: There are three types of
granulocytes - neutrophils, eosinophils and basophils. They all
have granules in their cytoplasm (fluid inside the cell). The
granules contain enzymes and chemicals that help the cells to
fight infection. Eosinophils and basophils also play a role in
allergic reactions. |
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Monocytes: These remove foreign material, including bacteria,
from the blood. They have a role in the body's immune response. |
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Lymphocytes: There are two main types of lymphocyte - T cells
and B cells. These are the main cells of the immune system. B
cells are responsible for antibody production. T cells recognise
and attack cells that have been infected by viruses. Once they
leave the bone marrow, these cells mature further in the lymph
tissue, e.g. lymph nodes and thymus. |
Platelets play an
important role in clot formation. |
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Types of leukaemia
There are a number of different types
of leukaemia and they are classified according to whether they are
acute or chronic and what type of white cell is affected.
Acute leukaemia
An increased production of immature blood cells fills up the bone
marrow and interferes with normal bone marrow function. The immature
cells are released into the bloodstream and may be deposited in
tissues and organs.
The decrease in the number of normal blood cells produced by the
bone marrow leads to anaemia due to a deficiency in red blood cells,
thrombocytopaenia because of reduced platelet production and
neutropaenia due to low neutrophil production.
This increased production of immature blood cells and reduction in
normal blood cells is responsible for the signs and symptoms of
acute leukaemia.
Acute leukaemia has a
more rapid onset and progression than chronic leukaemia. In acute
leukaemia, the cancer affects immature blood cells in the bone
marrow. There are two main types of acute leukaemia:
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Acute lympoblastic
leukaemia (ALL), which arises from blast cells already involved
in lymphocyte production, and |
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Acute myeloid
leukaemia (AML), which arises from precursor cells that are
destined to mature into granulocytes, platelets or red blood
cells. |
Incidence
Acute leukaemia is uncommon and there are about four new cases per
100,000 of the population per year. AML is more common in adults and
accounts for over 75 percent of cases. ALL accounts for over 75
percent of acute leukaemia in children and has a peak incidence in
early childhood.
Chronic leukaemia
Chronic leukaemia is a more slowly progressive condition. There are
two main types of chronic leukaemia:
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Chronic lymphocytic
leukaemia (CLL), which arises from mature committed B or, less
commonly, T lymphocytes, and |
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Chronic myeloid
leukaemia (CML), where granulocytes are affected. Although the
neoplastic or cancerous cells may appear normal they do not
function normally. |
CLL is a disease of
older people (mainly 60-80 years) and is rare under the age of 40
years. It is twice as common in men as in women. It is the most
common chronic leukaemia in adults and accounts for 25 percent of
all leukaemias.
CML may occur at
any age but is more common in middle age and very rare under five
years of age. It has a chronic phase lasting two to three years and
then enters a more acute phase. |
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| LEUKAEMIA RELATED ITEMS |
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