Any of a group of cancers in which the bone
marrow and other blood-forming tissues produce abnormal numbers of immature
or defective leukocytes (white blood cells).
This overproduction suppresses output of normal blood cells and platelets,
leaving the person vulnerable to infection, anemia,
and bleeding. Leukemias are classified into acute and chronic forms and
also according to the type of leukocyte involved.
Types of leukemia
The types of leukemia are grouped by how quickly the disease develops and
gets worse. Leukemia is either chronic (gets worse slowly) or acute (gets
The types of leukemia are also grouped by the type of white blood cell that
is affected. Leukemia can arise in lymphoid cells or myeloid cells. Leukemia
that affects lymphoid cells is called lymphocytic leukemia. Leukemia that
affects myeloid cells is called myeloid leukemia or myelogenous leukemia.
- Chronic leukemia. Early in the disease, the abnormal
blood cells can still do their work, and people with chronic leukemia
may not have any symptoms. Slowly, chronic leukemia gets worse. It causes
symptoms as the number of leukemia cells in the blood rises.
- Acute leukemia. The blood cells are very abnormal.
They cannot carry out their normal work. The number of abnormal cells
increases rapidly. Acute leukemia worsens quickly.
There are four common types of leukemia:
Hairy cell leukemia is a rare type of chronic leukemia. This article
does not deal with hairy cell leukemia or other rare types of leukemia.
- Chronic lymphocytic leukemia (chronic lymphoblastic
leukemia, CLL) accounts for about 7,000 new cases of leukemia each year.
Most often, people diagnosed with the disease are over age 55. It almost
never affects children.
- Chronic myeloid leukemia (chronic myelogenous leukemia,
CML) accounts for about 4,400 new cases of leukemia each year. It affects
- Acute lymphocytic leukemia (acute lymphoblastic leukemia,
ALL) accounts for about 3,800 new cases of leukemia each year. It is
the most common type of leukemia in young children. It also affects
- Acute myeloid leukemia (acute myelogenous leukemia,
AML) accounts for about 10,600 new cases of leukemia each year. It occurs
in both adults and children.
Who is at risk from leukemia?
No one knows the exact causes of leukemia. Doctors can seldom explain why
one person gets this disease and another does not. However, research has
shown that people with certain risk factors are more likely than others
to develop leukemia. A risk factor is anything that increases a person's
chance of developing a disease.
Studies have found the following risk factors for leukemia:
In the past, some studies suggested exposure to electromagnetic fields as
another possible risk factor for leukemia. Electromagnetic fields are a
type of low-energy radiation that comes from power lines and electric appliances.
However, results from recent studies show that the evidence is weak for
electromagnetic fields as a risk factor.
- Very high levels of radiation. People exposed to very high
levels of radiation are much more likely than others to develop leukemia.
Very high levels of radiation have been caused by atomic bomb explosions
(such as those in Japan during World War II) and nuclear power plant
accidents (such as the Chernobyl [also called Chornobyl] accident in
- Medical treatment that uses radiation can be another source
of high-level exposure. Radiation used for diagnosis, however, exposes
people to much lower levels of radiation and is not linked to leukemia.
- Working with certain chemicals. Exposure to high levels of
benzene in the workplace can cause leukemia.
Benzene is used widely in the chemical industry. Formaldehyde is also
used by the chemical industry. Workers exposed to formaldehyde also
may be at greater risk of leukemia.
- Chemotherapy. Cancer patients treated with certain cancer-fighting
drugs sometimes later develop leukemia. For example, drugs known as
alkylating agents are associated with the development of leukemia many
- Down's syndrome and
certain other genetic diseases. Some diseases caused by abnormal
chromosomes may increase the risk of leukemia.
- Human T-cell leukemia virus-I (HTLV-I). This virus causes a
rare type of chronic lymphocytic leukemia known as human T-cell leukemia.
However, leukemia does not appear to be contagious.
- Myelodysplastic syndrome. People with this blood disease are
at increased risk of developing acute myeloid leukemia.
Most people who have known risk factors do not get leukemia. On the other
hand, many who do get the disease have none of these risk factors. People
who think they may be at risk of leukemia should discuss this concern with
their doctor. The doctor may suggest ways to reduce the risk and can plan
an appropriate schedule for checkups.
What are the symptoms of leukemia?
Like all blood cells, leukemia cells travel through the body. Depending
on the number of abnormal cells and where these cells collect, patients
with leukemia may have a number of symptoms.
Common symptoms of leukemia may include:
Such symptoms are not sure signs of leukemia. An infection or another problem
also could cause these symptoms. Anyone with these symptoms should see a
doctor as soon as possible. Only a doctor can diagnose and treat the problem.
- Fevers or night sweats
- Frequent infections
- Feeling weak or tired
- Bleeding and bruising easily (bleeding gums, purplish patches in the
skin, or tiny red spots under the skin)
- Pain in the bones or joints
- Swelling or discomfort in the abdomen
(from an enlarged spleen)
- Swollen lymph nodes, especially
in the neck or armpit
- Weight loss
In the early stages of chronic leukemia, the leukemia cells function almost
normally. Symptoms may not appear for a long time. Doctors often find chronic
leukemia during a routine checkup – before there are any symptoms.
When symptoms do appear, they generally are mild at first and get worse
In acute leukemia, symptoms appear and get worse quickly. People with this
disease go to their doctor because they feel sick. Other symptoms of acute
leukemia are vomiting, confusion, loss
of muscle control, and seizures. Leukemia cells also can collect in the
testicles and cause swelling. Also, some patients develop sores in the eyes
or on the skin. Leukemia also can affect the digestive
tract, kidneys, lungs,
or other parts of the body.
How is leukemia diagnosed?
If a person has symptoms that suggest leukemia, the doctor may do a physical
exam and ask about the patient's personal and family medical history. The
doctor also may order laboratory tests, especially blood tests.
The exams and tests may include the following:
- Physical exam. The doctor checks for swelling of the lymph
nodes, spleen, and liver.
- Blood tests. The lab checks
the level of blood cells. Leukemia causes a very high level of white
blood cells. It also causes low levels of platelets and hemoglobin,
which is found inside red blood cells. The lab also may check the blood
for signs that leukemia has affected the liver and kidneys.
- Biopsy. The doctor removes some
bone marrow from the hipbone or another large bone. A pathologist examines
the sample under a microscope. The removal of tissue to look for cancer
cells is called a biopsy. A biopsy is the only sure way to know whether
leukemia cells are in the bone marrow.
There are two ways the doctor can obtain bone marrow. Some patients
will have both procedures:
- Bone marrow aspiration: The doctor uses a needle to remove
samples of bone marrow.
- Bone marrow biopsy: The doctor uses a very thick needle
to remove a small piece of bone and bone marrow.
Local anesthesia helps to make the
patient more comfortable.
- Cytogenetics. The lab looks at the chromosomes of cells from
samples of peripheral blood, bone marrow, or lymph nodes.
- Lumbar puncture. The
doctor removes some of the cerebrospinal
fluid (the fluid that fills the spaces in and around the brain and
spinal cord). The doctor uses a long, thin needle to remove fluid from
the spinal column. The procedure takes about 30 minutes and is performed
with local anesthesia. The patient must lie flat for several hours afterward
to keep from getting a headache. The lab checks the fluid for leukemia
cells or other signs of problems.
- Chest X-ray. The X-ray
can reveal signs of disease in the chest.
How is leukemia treated?
Read about how leukemia is treated.
Source: National Cancer