Leukemia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Leukemia Microchapters
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Patient Information
Overview
Classification AML CML ALL CLL
Differentiating Leukemia from other Diseases
Epidemiology and Demographics
Prognosis

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Symptoms

Damage to the bone marrow, by way of displacing the normal bone marrow cells with higher numbers of immature white blood cells, 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 bleeds (petechiae).

White blood cells, which are involved in fighting pathogens, may be suppressed or dysfunctional. This could cause the patient's immune system (white blood cells etc.) to start attacking other body cells.

Finally, the red blood cell deficiency leads to anemia, which may cause dyspnea. All symptoms can be attributed to other diseases; for diagnosis, blood tests and a bone marrow examination are required.

Some other related symptoms:

• Fever, chills, night sweats and other flu-like symptoms
• Weakness and fatigue
• Swollen or bleeding gums
• Neurological symptoms (headaches)
• Enlarged liver and spleen
• Frequent infection
• Bone pain
• Joint pain
• Dizziness
• Nausea
• Swollen tonsils
• Diarrhea
• Paleness
• Malaise
• Unintentional weight loss

The word leukemia, which means 'white blood,' is derived from the disease's namesake high white blood cell counts that most leukemia patients have before treatment. The high number of white blood cells are apparent when a blood sample is viewed under a microscope. Frequently, these extra white blood cells are immature or dysfunctional. The excessive number of cells can also interfere with the normal function of other cells.

Some leukemia patients do not have high white blood cell counts visible during a regular blood count. This less-common condition is called aleukemia. The bone marrow still contains cancerous white blood cells which disrupt the normal production of blood cells. However, the leukemic cells are staying in the marrow instead of entering the bloodstream, where they would be visible in a blood test. For an aleukemic patient, the white blood cell counts in the bloodstream can be normal or low. Aleukemia can occur in any of the four major types of leukemia, and is particularly common in hairy cell leukemia.

Classification

Leukemia is clinically and pathologically subdivided into several large groups. The first division is between its acute and chronic forms:

• Acute leukemia is characterized by the rapid increase 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. Central nervous system (CNS) involvement is uncommon, although the disease can occasionally cause cranial nerve palsies.
• Chronic leukemia is distinguished by the excessive build up of relatively mature, but still abnormal, blood cells. Typically taking months or 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.

Additionally, the diseases are subdivided according to which kind of blood cell is affected. This split divides leukemias into lymphoblastic or lymphocytic leukemias and myeloid or myelogenous leukemias:

• In lymphoblastic or lymphocytic leukemias, the cancerous change takes place in a type of marrow cell that normally goes on to form lymphocytes.
• In myeloid or myelogenous leukemias, the cancerous change takes place in a type of marrow cell that normally goes on to form red cells, some types of white cells, and platelets.

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

Four major kinds of leukemia

Cell type	Acute	Chronic
Lymphocytic leukemia (or "lymphoblastic")	Acute lymphoblastic leukemia (ALL)	Chronic lymphocytic leukemia (CLL)
Myelogenous leukemia (also "myeloid" or "nonlymphocytic")	Acute myelogenous leukemia (AML)	Chronic myelogenous leukemia (CML)

Within these main categories, there are typically several subcategories. Finally, hairy cell leukemia is usually considered to be outside of this classification scheme.

• Acute lymphoblastic leukemia (ALL) is the most common type of leukemia in young children. This disease also affects adults, especially those age 65 and older. Standard treatments involve chemotherapy and radiation. The survival rates vary by age: 85% in children and 50% in adults.

• 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. Two-thirds of affected people are men. The five-year survival rate is 75%. It is incurable, but there are many effective treatments.

• Acute myelogenous leukemia (AML) occurs more commonly in adults than in children, and more commonly in men than women. AML is treated with chemotherapy. The five-year survival rate is 40%.

• Chronic myelogenous leukemia (CML) occurs mainly in adults. A very small number of children also develop this disease. Treatment is with imatinib (Gleevec) or other drugs. The five-year survival rate is 90%.

• Hairy cell leukemia (HCL) is sometimes considered a subset of CLL, but does not fit neatly into this pattern. About 80% of affected people are adult men. There are no reported cases in young children. HCL is incurable, but easily treatable. Survival is 96% to 100% at ten years.

Causes and risk factors

There is no single known cause for all of the different types of leukemia. The different leukemias likely have different causes, and very little is certain about what causes them. Researchers have strong suspicions about four possible causes:

• natural or artificial ionizing radiation
• certain kinds of chemicals
• some viruses
• genetic predispositions

Leukemia, like other cancers, result from somatic mutations in the DNA which activate oncogenes or deactivate tumor 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 to be influenced by genetic factors. Cohort and case-control studies have linked exposure to petrochemicals, such as benzene, and hair dyes to the development of some forms of leukemia.

Viruses have also been linked to some forms of leukemia. For example, 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 myelogenous leukemia.

Until the cause or causes of leukemia are found, there is no way to prevent the disease. Even when the causes become known, they may prove to be things which are not readily controllable, such as naturally occurring background radiation, and therefore not especially helpful for prevention purposes.

Research

Significant research into the causes, diagnosis, treatment, and prognosis of leukemia is being done. Hundreds of clinical trials are being planned or conducted at any given time. Studies may focus on effective means of treatment, better ways of treating the disease, improving the quality of life for patients, or appropriate care in remission or after cure.

External links

Images of leukemias

• UVA Healthsystem -- Images of acute leukemias by stage

Research organizations

• The Therapeutic Advances in Childhood Leukemia (TACL) Consortium -- US research group
• "Chromosomes, Leukaemias, Solid Tumors, Hereditary Cancers" in AtlasGeneticsOncology.