Wednesday, December 9, 2009

The Leukemias



Uncontrolled production of white blood cells can be
caused by cancerous mutation of a myelogenous or
lymphogenous cell. This causes leukemia, which is
usually characterized by greatly increased numbers
of abnormal white blood cells in the circulating
blood.
Types of Leukemia. Leukemias are divided into two
general types: lymphocytic leukemias and myelogenous
leukemias.The lymphocytic leukemias are caused
by cancerous production of lymphoid cells, usually
beginning in a lymph node or other lymphocytic tissue
and spreading to other areas of the body. The second
type of leukemia, myelogenous leukemia, begins by
cancerous production of young myelogenous cells in
the bone marrow and then spreads throughout the
body so that white blood cells are produced in many
extramedullary tissues—especially in the lymph nodes,
spleen, and liver.
In myelogenous leukemia, the cancerous process
occasionally produces partially differentiated cells,
resulting in what might be called neutrophilic
leukemia, eosinophilic leukemia, basophilic leukemia,
or monocytic leukemia. More frequently, however, the
leukemia cells are bizarre and undifferentiated and
not identical to any of the normal white blood cells.
Usually, the more undifferentiated the cell, the more
acute is the leukemia, often leading to death within a
few months if untreated.With some of the more differentiated
cells, the process can be chronic, sometimes
developing slowly over 10 to 20 years. Leukemic
cells, especially the very undifferentiated cells, are
usually nonfunctional for providing the normal protection
against infection.
Effects of Leukemia on the Body
The first effect of leukemia is metastatic growth of
leukemic cells in abnormal areas of the body.
Leukemic cells from the bone marrow may reproduce
so greatly that they invade the surrounding bone,
causing pain and, eventually, a tendency for bones to
fracture easily.
Almost all leukemias eventually spread to the
spleen, lymph nodes, liver, and other vascular regions,
regardless of whether the origin of the leukemia is in
the bone marrow or the lymph nodes. Common effects
in leukemia are the development of infection, severe
anemia, and a bleeding tendency caused by thrombocytopenia
(lack of platelets). These effects result
mainly from displacement of the normal bone marrow
and lymphoid cells by the nonfunctional leukemic
cells.
Finally, perhaps the most important effect of
leukemia on the body is excessive use of metabolic
substrates by the growing cancerous cells. The
leukemic tissues reproduce new cells so rapidly that
tremendous demands are made on the body reserves
for foodstuffs, specific amino acids, and vitamins. Consequently,
the energy of the patient is greatly depleted,
and excessive utilization of amino acids by the
leukemic cells causes especially rapid deterioration of
the normal protein tissues of the body.Thus, while the
leukemic tissues grow, other tissues become debilitated.
After metabolic starvation has continued long
enough, this alone is sufficient to cause death.

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