Leukemia

Leukaemia or leukaemia is a cancer of the blood or bone marrow and is characterized by an abnormal proliferation (production by multiplication) of blood cells, usually white blood cells (leukocytes). It is a cancer of the tissues in which blood is formed. It is part of the broad group of diseases called haematological neoplasms.

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 leukaemia 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 anaemia, 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
• Loss of appetite and/or weight
• Swollen or bleeding gums
• Excess bleeding (from a minor cut)
• Neurological symptoms (headache)
• Enlarged liver and spleen
• Easy bruising
• Frequent infection
• Bone pain
• Joint pain
• Swollen tonsils

The word leukaemia, which means 'white blood,' is derived from the disease's namesake high white blood cell counts that most leukaemia patients have before treatment. The high number of white blood cells is 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 leukaemia patients do not have high white blood cell counts visible during a regular blood count. This less-common condition is called aleukaemia. The bone marrow still contains cancerous white blood cells, and they are disrupting the normal production of blood cells. However, they are staying in the marrow instead of entering the bloodstream, where they would be visible in a blood test. For an aleukaemic patient, the white blood cell counts in the bloodstream can be normal or low. Aleukaemia can occur in any of the four major types of leukaemia, and is particularly common in hairy cell leukaemia.

Major types

Leukaemia is a broad term covering a spectrum of diseases.

Leukaemia is clinically and pathologically split into its acute and chronic forms.

Acute leukaemia is characterized by the rapid proliferation of immature blood cells. This crowding makes the bone marrow unable to produce healthy blood cells. Acute forms of leukaemia can occur in children and young adults. Immediate treatment is required in acute leukaemia 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. However, CNS involvement is uncommon, though the disease occasionally causes cranial nerve palsies.

Chronic leukaemia is distinguished by the excessive build up 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 leukaemia mostly occurs in older people, but can theoretically occur in any age group. Whereas acute leukaemia must be treated immediately, chronic forms are sometimes monitored for some time before treatment to ensure maximum effectiveness of therapy.

Causes and risk factors

There is no single known cause for all of the different types of leukaemia. The different leukaemias 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

Leukaemia, like other cancers, result from somatic mutations in the DNA which activate oncogenes or deactivate 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 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 leukaemia.

Viruses have also been linked to some forms of leukaemia. 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 leukaemia/lymphoma).

Fanconi anaemia is also a risk factor for developing acute myelogenous leukaemia.

Until the cause or causes of leukaemia 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.

Treatments

• Induction chemotherapy is given with the goal of rapidly restoring normal bone marrow function- called as complete remission (CR).
• Post-CR (complete remission) therapy aims to destroy leukemia cells that survived induction chemotherapy but are undetectable by conventional studies.

To access the complete ICMR Consensus document for the management of Acute Myeloid Leukemia (AML), click here.