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Acute Myeloid Leukemia
Acute myelogenous leukemia (AML), also known as acute myeloid
leukemia, is a cancer of the myeloid line of white blood cells, characterized by
the proliferation of abnormal, immature cells which accumulate in the bone
marrow and elsewhere.
Myeloid leukemias are characterized as "acute" or "chronic" based on how quickly
they progress if untreated. Acute leukemias, such as AML, progress rapidly and
can be fatal in weeks to months if untreated. In contrast, chronic myelogenous
leukemia is a separate disease which can lay dormant for years before
progressing to a more acute, life-threatening phase.
The malignant cell in AML is the myeloblast. In normal hematopoiesis, the
myeloblast is a normal immature precursor of myeloid white blood cells; a normal
myeloblast will gradually "grow up" into a mature white blood cell. However, in
AML, a single myeloblast accumulates genetic changes which "freeze" the cell in
its immature state and prevent differentiation. When such a "differentiation
arrest" is combined with mutations which disrupt transcription factor genes
(controlling proliferation), the result is the uncontrolled growth of an
immature clone of cells, leading to the clinical entity of AML.
Much of the diversity and heterogeneity of AML stems from the fact that leukemic
transformation can occur at a number of different steps along the
differentiation pathway. Modern classification schemes for AML (see below)
recognize that the characteristics and behavior of the leukemic cell (and the
leukemia) may depend on the stage at which differentiation was halted.
Specific cytogenetic abnormalities can be found in many patients with AML;
the types of chromosomal abnormalities often have prognostic significance.
The clinical signs and symptoms of AML result from the fact that, as the
leukemic clone of cells grows, it tends to displace or interefere with the
development of normal blood cells in the bone marrow. This leads to neutropenia,
anemia, and thrombocytopenia. The symptoms of AML are in turn often due to the
low numbers of these normal blood elements. In rare cases, patients can develop
a chloroma, or solid tumor of leukemic cells outside the bone marrow, which can
cause various symptoms depending on its location.
From Wikipedia, the free encyclopedia
Acute lymphoblastic
leukemia
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