Leukemia facts
Leukemia is a cancer of blood cells (and
therefore sometimes referred to as blood cancer
).
While the exact cause(s) of leukemia is not
known, risk factors have been identified, including
radiation exposure, certain chemotherapy for
cancer , smoking , family history of leukemia,
and exposure to certain chemicals such as
benzene.
Common symptoms of chronic or acute
leukemia may include
pain in the bones or joints,
swollen lymph nodes that usually don't
hurt,
fevers or night sweats ,
feeling weak or tired,
bleeding and bruising easily,
frequent infections,
discomfort or swelling in the abdomen,
weight loss or loss of appetite.
Leukemias are grouped by how quickly the
disease develops (acute or chronic) as well as by
the type of blood cell that is affected
(lymphocytes or myelocytes). The four main types
of leukemia include acute lymphocytic leukemia
(ALL), chronic lymphocytic leukemia (CLL),
acute myelocytic leukemia (AML), and chronic
myelocytic leukemia (CML).
People with leukemia are at significantly
increased risk for developing infections, anemia ,
and bleeding. Other symptoms and signs include
easy bruising , weight loss , night sweats, and
unexplained fevers.
The diagnosis of leukemia is supported by
findings of the medical history and examination,
and examining blood and bone marrow samples
under a microscope.
Treatment of leukemia depends on the type of
leukemia, certain features of the leukemia cells,
the extent of the disease, and prior history of
treatment, as well as the age and health of the
patient.
Most patients with leukemia are treated with
chemotherapy. Some patients also may have
radiation therapy and/or bone marrow
transplantation.
There is no known way to prevent leukemia.
The prognosis of leukemia depends upon
several factors, including the patient's age, the
type of leukemia, and the extent to which the
cancer has spread.
Leukemia is a malignancy (cancer) of blood cells.
In leukemia, abnormal blood cells are produced in
the bone marrow. Usually, leukemia involves the
production of abnormal white blood cells -- the
cells responsible for fighting infection. However,
the abnormal cells in leukemia do not function in
the same way as normal white blood cells. The
leukemia cells continue to grow and divide,
eventually crowding out the normal blood cells.
The end result is that it becomes difficult for the
body to fight infections, control bleeding, and
transport oxygen.
There are different types of leukemia, based upon
how quickly the disease develops and the type of
abnormal cells produced. Leukemia is called an
acute leukemia if it develops rapidly. Large
numbers of leukemia cells accumulate very
quickly in the blood and bone marrow, leading to
symptoms such as tiredness, easy bruising , and
susceptibility to infections. Acute leukemia
requires fast and aggressive treatment.
There are around 62,000 new cases of leukemia
each year in the U.S. and about 24,500 deaths
due to leukemia. Leukemia makes up about 3.7%
of all new cancer cases.
Chronic leukemias develop slowly over time.
These leukemias may not cause specific
symptoms at the beginning of their course. If left
untreated, the cells may eventually grow to high
numbers, as in acute leukemias causing similar
symptoms.
Leukemias are further classified as myeloid or
lymphoid, depending upon the type of white blood
cell that makes up the leukemia cells. A basic
understanding of the normal development of blood
cells is needed to understand the different types
of leukemia. Normal blood cells develop from
stem cells that have the potential to become
many cell types. Myeloid stem cells mature in the
bone marrow and become immature white cells
called myeloid blasts. These myeloid blasts
further mature to become either red blood cells,
platelets, or certain kinds of white blood cells.
Lymphoid stem cells mature in the bone marrow
to become lymphoid blasts. The lymphoid blasts
develop further into T or B lymphocytes, special
types of white blood cells. Myeloid leukemias are
made up of cells that arise from myeloid cells,
while lymphoid leukemias arise from lymphoid
cells. Knowing the type of cell involved in
leukemia is important in choosing the appropriate
treatment.
Common types of leukemia
The four most common types of leukemia are
acute lymphocytic leukemia, chronic lymphocytic
leukemia, acute myeloid leukemia , and
chronic myeloid leukemia .
Acute lymphocytic leukemia (ALL, also known
as acute lymphoblastic leukemia ) is the most
common type of leukemia in children, but it can
also affect adults. In this type of leukemia,
immature lymphoid cells grow rapidly in the
blood. It affects over 6,000 people per year in the
U.S.
Acute myeloid leukemia (AML, also called acute
myelogenous leukemia ) involves the rapid
growth of myeloid cells. It occurs in both adults
and children and affects about 21,000 people
each year in the U.S.
Chronic lymphocytic leukemia (CLL) is a slow-
growing cancer of lymphoid cells that usually
affects people over 55 years of age. It is
estimated to affect about 20,000 people in the
U.S. every year. It almost never occurs in children
or adolescents.
Chronic myeloid leukemia (CML, also known as
chronic myelogenous leukemia ) primarily
affects adults and occurs in about 8.950 people
every year in the U.S.
Less common types of leukemia account for
about 6,000 cases of leukemia each year in the
U.S.
Hairy cell leukemia is an uncommon type of
chronic leukemia .
Chronic myelomonocytic leukemia (CMML) is
another type of chronic leukemia that develops
from myeloid cells.
Juvenile myelomonocytic leukemia (JMML) is a
type of myeloid leukemia that usually occurs in
children under 6 years of age.
Large granular lymphocytic leukemia (LGL
leukemia) is a type of chronic leukemia that
develops from lymphoid cells. It can be slow- or
fast-growing.
Acute promeylocytic leukemia (APL) is a
subtype of AML.
What causes leukemia? Is leukemia
hereditary?
The exact cause of leukemia is not known, but it
is thought to involve a combination of genetic and
environmental factors. Leukemia cells have
acquired mutations in their DNA that cause them
to grow abnormally and lose functions of typical
white blood cells. It is not clear what causes
these mutations to occur. One type of change in
the cells' DNA that is common in leukemias is
known as a chromosome translocation. In this
process, a portion of one chromosome breaks off
and attaches to a different chromosome. One
translocation seen in almost all cases of CML and
in sometimes in other types of leukemia is an
exchange of DNA between chromosomes 9 and
22, which leads to what is known as the
Philadelphia chromosome. This creates an
oncogene (cancer-promoting gene) known as
BCR-ABL. This change in DNA is not inherited but
occurs sometime in the life of the affected
individual.
Most cases of leukemia are not believed to be
hereditary, but certain genetic mutations and
conditions can be passed along to offspring that
increase the chances of developing leukemia. A
condition known as Li-Fraumeni syndrome is
characterized by an inherited mutation in a tumor
suppressor gene known as TP53, and individuals
with this condition have an increased risk of
leukemia and other cancers . Other hereditary
conditions that can increase the risk of developing
leukemia include Down syndrome ,
neurofibromatosis type 1 , ataxia
telangiectasia , and Noonan syndrome .
What are leukemia risk factors?
Exposure to radiation is known to increase the
risk of developing AML, CML, or ALL. Increases in
leukemia were observed in people surviving
atomic bombs. Radiation therapy for cancer can
also increase the risk of leukemia. Exposure to
certain chemicals, including benzene (used
commonly in the chemical industry), increases the
risk of leukemia. Cigarette smoking is known to
increase the risk of developing AML.
Certain genetic disorders can increase the risk;
Down syndrome, Li-Fraumeni syndrome, and
other medical conditions can increase the risk of
developing leukemia. Blood disorders known
as myelodysplastic syndromes confer an
increased risk of developing AML. Human T-cell
leukemia virus type 1 (HTLV-1) is a virus that
causes a rare type of leukemia. Certain
chemotherapy drugs for cancer can increase the
risk for AML or ALL.
Having risk factors does not mean that a person
will definitely get leukemia, and most people with
risk factors will not develop the disease. Likewise, short white lace wedding dress
not everyone who develops leukemia has an
identifiable risk factor.
The symptoms and signs of leukemia depend
upon the type of leukemia. As stated earlier,
slow-growing or chronic leukemia may not cause
any symptoms at the outset, while aggressive or
rapidly growing leukemia may lead to severe
symptoms. The symptoms of leukemia arise from
a loss of function of the normal blood cells or
from accumulation of the abnormal cells in the
body.
Signs and symptoms of leukemia typically include
the following:
Fevers
Night sweats
Swollen lymph nodes that are usually painless
Feelings of fatigue , tiredness
Easy bleeding or bruising , causing bluish or
purplish patches on the skin or tiny red spots on
the skin , or recurring nosebleeds
Frequent infections
Bone or joint pain
Weight loss that is otherwise unexplained, or
loss of appetite
Enlargement of the spleen or liver , which can
lead to abdominal pain or swelling
Red spots on the skin (petechiae)
If leukemia cells have infiltrated the brain,
symptoms such as headaches , seizures ,
confusion, loss of muscle control, and vomiting
can occur.
How do physicians diagnose leukemia?
Hematologists are specialist physicians who
diagnose and treat blood diseases, including
leukemia; hematologist-oncologists treat blood
diseases like leukemia, as well as other types of
cancers.
In addition to a medical history (asking about
symptoms and risk factors) and a physical exam
to look for signs of leukemia ( lymph node
enlargement, enlargement of spleen), the
diagnosis of leukemia typically involves laboratory
studies of a blood sample. Abnormal numbers of
blood cells may suggest a diagnosis of leukemia,
and the blood sample may also be examined
under the microscope to see if the cells appear
abnormal. A sample of the bone marrow may also
be obtained to establish the diagnosis. For a
bone marrow aspirate, a long, thin needle is used
to withdraw a sample of bone marrow from the
hip bone, under local anesthesia. A bone marrow
biopsy involves insertion of a thick, hollow needle
into the hip bone to remove a sample of the bone
marrow, using local anesthesia.
Cells from the blood and bone marrow are further
tested if leukemia cells are present. These
additional tests look for genetic alterations and
expression of certain cell surface markers by the
cancer cells (immunophenotyping). The results of
these tests are used to help determine the precise
classification of the leukemia and to decide on
optimal treatment.
Other tests that may be useful include a chest X-
ray to determine if there are enlarged lymph
nodes or other signs of disease and a lumbar
puncture to remove a sample of cerebrospinal
fluid to determine if the leukemia cells have
infiltrated the membranes and space surrounding
the brain and spinal cord.