Leukaemia is any of several types of cancer in which there is a disorganized proliferation of abnormal white blood cells in the bone marrow.This increase in white cells interferes with production of normal blood cells in the marrow. A reduced number of red blood cells leads to anaemia, while a reduction in normal white cells increases the body’ s susceptibility to infection. Inadequate numbers of platelets may cause abnormal bleeding.
Also, organs such as the liver, spleen, lymph nodes, or brain may cease to function properly if they become infiltrated by abnormal cells. Leukaemias are classified as acute or chronic (acute types generally develop faster than chronic).
They are also classified according to the type of white cell that is proliferating abnormally. If the abnormal cells are lymphocytes or lymphoblasts (precursors of lymphocytes), the leukaemia is called lymphocytic or lymphoblastic leukaemia. If the abnormal cells are derived from other types of white cell or their precursors, the disease is called myeloid, myeloblastic, or granulocytic leukaemia.
A type of leukaemia in which excessive numbers of immature white blood cells called blasts are produced in the bone marrow. If left untreated, acute leukaemia can cause death within a few weeks or months.
The abnormal cells may be of two main types: lymphoblasts (immature lymphocytes) in acute lymphoblastic leukaemia, or ALL, and myeloblasts (immature forms of other types of white blood cell) in acute myeloblastic leukaemia, or AML.
In most cases, the cause of acute leukaemia is unknown. However, exposure to certain chemicals (such as benzene) or high levels of radiation may be a risk factor. Previous treatments for cancer may also increase the risk of leukaemia developing. Inherited factors are thought to play a part; there is increased inci-dence in individuals who have certain genetic disorders (such as Fanconi’s anaemia) and chromosomal abnormalities (such as Down’s syndrome). In addition, people who have blood disorders such as aplastic anaemia (see anaemia, aplastic) or primary polycythaemia are at increased risk because their bone marrow is already abnormal.
Symptoms and signs
The symptoms and signs of acute leukaemia are due to the abnormal white cells crowding the bone marrow and infiltrating the bloodstream and body tissues. They include bleeding gums, headache, easy bruising, bone pain, enlarged lymph nodes, and symptoms of anaemia, such as tiredness, pallor, and breathlessness on exertion. There may also be repeated chest or throat infections.
Diagnosis and treatment
Blood tests (and, in some cases, tests on the cerebrospinal fluid, which surrounds the brain and spinal cord) may reveal the presence of abnormal white cells, but diagnosis is confirmed by a bone marrow biopsy. Treatment is divided into two phases: remission induction to control the disease, and consolidation, which prevents the disease from recurring. Procedures include transfusions of blood and platelets; the use of anticancer drugs to kill abnormal cells in the bone marrow; and possibly radiotherapy to destroy any abnormal cells in the brain. A bone marrow transplant or stem cell transplant may also be required.
Chemotherapy has increased success rates, but the outlook depends on the type of leukaemia and the age of the patient. People with ALL generally respond better to treatment than those with AML, and many children with ALL can now make a full recovery. Treatment of AML is less likely to be successful in people over the age of fifty.
Chronic lymphocytic leukaemia (CLL)
CLL is a type of leukaemia caused by a proliferation of mature lymphocytes (white blood cells that are normally involved in fighting infection and harmful cells). There is no cure for the disease, but it is not always fatal. The cause is unknown.
Symptoms develop slowly, often over many years. There may be enlargement of the liver, spleen, and lymph nodes, persistent raised temperature, and night sweats. Recurrent infections and anaemia also are common.
Diagnosis and treatment
Diagnosis is by blood tests and a bone marrow biopsy. In many mild cases, treatment is not needed. If symptoms become troublesome, drug treatment is started, often with chlorambucil.
Chronic myeloid leukaemia (CML)
Also known as chronic granulocytic leukaemia, a type of leukaemia caused by overproduction of granulocytes (a type of white blood cell) or, in particular, neutrophils (a type of granulocyte). The cause of the condition is unknown but almost all affected people have a chromosomal abnormality called the Philadelphia chromosome, in which part of one chromosome is attached to another.
Chronic myeloid leukaemia usually has two phases: a chronic phase, which may last for several years, and an accelerated, or acute, phase that may last for several months.
During the chronic phase, symptoms are not always obvious, although they may include fever, night sweats, and weight loss. High numbers of white cells may cause the blood to become very thick and unable to flow through the smallest vessels, leaving tissues starved of oxygen.The results include visual disturbances, as blood vessels in the eye are affected, and abdominal pain due to the death of tissues in the spleen; priapism (persistent, painful erection of the penis) may also occur. The symptoms of the accelerated phase are like those of acute leukaemia (see leukaemia, acute).
Diagnosis and treatment
The diagnosis is made from blood tests and a bone marrow biopsy. Treatment of the chronic phase includes anticancer drugs or alpha interferons.A bone marrow transplant is also possible if a suitable donor can be found. When the disease transforms into the acute phase, the treatment is similar to that given for acute leukaemia.
Cell and Molecular Biology of Human Leukaemias - technical article
The Classification of Leukaemia - technical article
Acute Lymphoblastic Leukaemia - technical article
Acute Myeloid Leukaemia - technical article
Chronic Lymphocytic Leukaemia and Other Leukaemias of Mature B and T Cells - technical article
Chronic Myeloid Leukaemia - technical article