Commonwealth English) is a
cancer of the
bone marrow characterized by an abnormal proliferation
of blood cells, usually white blood cells (leukocytes).
It is part of the broad group of diseases called
Damage to the bone marrow
results in a lack of blood platelets, which are important in
the blood clotting process. This means people with leukemia
may become bruised, bleed excessively, or develop pinprick
White blood cells, which are involved in fighting pathogens,
may be suppressed or dysfunctional, putting the patient at
risk of infection.
Finally, the red blood cell deficiency leads to anemia,
which may cause shortness of breath and fatigue. Bone or
joint pain may occur because of cancer spreading to these
areas. Headaches and vomiting are indicative of the cancer
having disseminated to the central nervous system.
Enlarged lymph nodes or splenomegaly (an enlarged spleen)
may occur in some types. All symptoms may also be
attributable to other diseases; for diagnosis, blood tests
and a bone marrow biopsy are required.
Some other related symptoms:
chills, and other flu-like symptoms;
- Weakness and fatigue;
- Loss of
appetite and/or weight;
- Swollen or bleeding gums;
Sweating, especially at night;
- Bone or joint pain.
- Neurological symptoms
(headache, paralysis, seizures) due to involvement of the brain (acute leukemias)
- Skin symptoms.
Four major types
is a broad term covering a spectrum of diseases.
Acute vs. chronic
Leukemia is clinically and
pathologically split in to its
- Acute leukemia
is characterized by the rapid growth of immature blood
cells. This crowding makes the bone marrow unable to
produce healthy blood cells. Acute forms of leukemia can
occur in children and young adults. (In fact, it is a more
common cause of death for children in the
US than any other type of malignant disease).
Immediate treatment is required in acute leukemias due to
the rapid progression and accumulation of the malignant
cells, which then spill over into the bloodstream and
spread to other organs of the body. If left untreated, the
patient will die within months or even weeks.
- Chronic leukemia
is distinguished by the excessive buildup of relatively
mature, but still abnormal, blood cells. Typically taking
months to years to progress, the cells are produced at a
much higher rate than normal cells, resulting in many
abnormal white blood cells in the blood. Chronic leukemia
mostly occurs in older people, but can theoretically occur
in any age group. Whereas acute leukemia must be treated
immediately, chronic forms are sometimes monitored for
some time before treatment to ensure maximum effectiveness
Lymphoid vs. myeloid
Furthermore, the diseases
are classified according to the type of abnormal cell found
most in the blood.
- When leukemia affects
lymphoid cells, it is called
myeloid cells are affected, the disease is called
Prevalence of the four
Combining these two
classifications provides a total of four main categories:
seizures)Acute lymphocytic leukemia (ALL) is the most common
type of leukemia in young children. This disease also
affects adults, especially those age 65 and older.
Acute myelogenous leukemia (AML) occurs more commonly in
adults than in children. This type of leukemia was
previously called acute nonlymphocytic leukemia.
Chronic lymphocytic leukemia (CLL) most often affects adults
over the age of 55. It sometimes occurs in younger adults,
but it almost never affects children.
Chronic myelogenous leukemia (CML) occurs mainly in adults.
A very small number of children also develop this disease.
The most common forms in
adults are AML and CLL, whereas in children ALL is more
The exact cause of leukemia
is unknown but is influenced by both genetic and
environmental factors. Leukemias, like other cancers, result
from somatic mutations in the DNA which activate oncogenes
or inactivate tumour suppressor genes, and disrupt the
regulation of cell death, differentiation or division. These
mutations may occur spontaneously or as a result of exposure
to radiation or carcinogenic substances and are likely
influenced by genetic factors. Cohort and case control
studies have linked exposure to petrochemicals, such as
benzene, and hair dyes to the development of leukemia.
Viruses have also been linked to some forms of leukemia.
Certain cases of ALL are associated with viral infections by
either the human immunodeficiency virus (HIV, responsible
for AIDS) or human T-lymphotropic virus (HTLV-1 and -2,
causing adult T-cell leukemia/lymphoma).
Fanconi anemia is also a risk factor for developing acute
Prognosis and treatment
Prognosis and treatment
differ according to the type of leukemia. Treatment of
leukemia must be tailored to the type of leukemia and
individual patient characteristics. For example, while CLL
is an incurable disease with standard chemotherapy, patients
may require no treatment (ie. "watchful waiting") for years
if they are asymptomatic. In contrast, some patients with
AML will die within hours or days of presentation unless
intensive combination chemotherapy regimen is given and in
some cases will require allogeneic stem cell transplant.
This type of regimen would not be suited for an elderly
patient or one with significant comorbid conditions.
Current research is directed at targeting the molecular
mechanisms of the leukemia. One of the recent successes in
targeted therapy is imatinib (Gleevec, Glivec). Imatinib
inhibits the Abl tyrosine kinase which is constitutively
activated by the bcr/abl translocation found in patients
with CML and some patients with ALL.