Leukemia

Leukemia (leukaemia in Commonwealth English) is a cancerof the bloodor bone marrowcharacterized by an abnormal proliferation of blood cells, usually white blood cells (leukocytes). It is part of the broad group of diseases called hematological neoplasms.

Symptoms

Damage to the bone marrow results in a lack of blood platelets, which are important in the blood clottingprocess. This means people with leukemia may become bruised, bleedexcessively, or develop pinprick bleeds (petechiae).

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 breathand fatigue. Boneor jointpainmay occur because of cancer spreading to these areas. Headachesand vomitingare indicative of the cancer having disseminated to the central nervous system.

Enlarged lymph nodesor splenomegaly(an enlarged spleen) may occur in some types. All symptomsmay also be attributable to other diseases; for diagnosis, blood testsand a bone marrow biopsyare required.

Some other related symptoms:

• Fever, chills, and other flu-like symptoms;
• Weakness and fatigue;
• Loss of appetiteand/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

Leukemia is a broad term covering a spectrum of diseases.

Acute vs. chronic

Leukemia is clinically and pathologically split in to its acute and chronic forms.

• Acute leukemias are characterised 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 USthan 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 leukemias are 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 of therapy.

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 lymphocytic leukemia.

• When myeloid cellsare affected, the disease is called myeloid or myelogenous leukemia.

Prevalence of the four major types

Combining these two classifications provides a total of four main categories:

• 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 prevalent.

Causes

The exact cause of leukemia is unknown but is influenced by both genetic and environmental factors. Leukemias, like other cancers, result from somatic mutationsin the DNAwhich activate oncogenesor 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 radiationor carcinogenicsubstances and are likely influenced by genetic factors. Cohort and case control studies have linked exposure to petrochemicals, such as benzene, and hair dyesto the development of leukemia.

Viruseshave 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 anemiais also a risk factor for developing acute myelogenous leukemia.

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.

External links

• FAQ on leukemia
• Information and advocacy for leukemia
• Leukaemia Research Fund(UK)
• The Anthony Nolan Trust(UK)
• Unofficial summary of UKCCS, and of UKCCS publications
• Association of Cancer Online Resource (ACOR) Leukemia Links

de:Leukämie es:Leucemia fr:Leucémie ko:??? id:Leukemia ia:Leucemia it:Leucemia he:??????? lt:Leukemija nl:Leukemie ja:??? pl:Bia?aczka (medycyna) pt:Leucemia sk:Leukémia su:Leukemia fi:Leukemia sv:Leukemi uk:???????? zh:???

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Leukemia Wikipedia article Leukemia.