Leukaemia is a cancer of cells in the bone marrow (the cells which develop into blood cells).With leukaemia, the cancerous cells in the bone marrow spill out into the bloodstream. There are several types of leukaemia. Most types arise from cells which normally develop into white blood cells

What is normal blood made up of?

Red cells (erythrocytes). These make blood a red colour. One drop of blood contains about five million red cells. Red cells contain a chemical called haemoglobin.

White cells (leukocytes). There are different types of white cells, which are called neutrophils (polymorphs), lymphocytes, eosinophils, monocytes, and basophils. They are part of the immune system. Their main role is to defend the body against infection.

Platelets. These are tiny and help the blood to clot if we cut ourselves.

Plasma is the liquid part of blood and makes up about 60% of the blood's volume. Plasma is mainly made from water, but contains many different proteins and other chemicals, such as hormones, antibodies, enzymes, glucose, fat particles, salts, etc.

Bone marrow
Blood cells are made in the bone marrow by 'stem' cells. The bone marrow is the soft 'spongy' material in the centre of bones.

Stem cells
Stem cells are primitive (immature) cells. There are two main types in the bone marrow - myeloid and lymphoid stem cells. Stem cells constantly divide and produce new cells. Some new cells remain as stem cells and others go through a series of maturing stages ('precursor' or 'blast' cells) before forming into mature blood cells. Mature blood cells are released from the bone marrow into the bloodstream.
Lymphocyte white blood cells develop from lymphoid stem cells. There are three types of mature lymphocytes:

  • B lymphocytes make antibodies which attack infecting bacteria, viruses, etc.
  • T lymphocytes help the B lymphocytes to make antibodies.
  • Natural killer cells, which also help to protect against infection.

All the other different blood cells (red blood cells, platelets, neutrophils, basophils, eosinophils and monocytes) develop from myeloid stem cells.

Blood production
You make millions of blood cells every day. Each type of cell has an expected life-span. For example, red blood cells normally last about 120 days. Some white blood cells last just hours or days - some last longer.

The main types of leukaemia are:

  • Acute lymphoblastic leukaemia - 'ALL'.
  • Acute myeloid leukaemia - 'AML'.
  • Chronic lymphocytic leukaemia - 'CLL'.
  • Chronic myeloid leukaemia - 'CML'.

Acute lymphoblastic leukaemia

In acute lymphoblastic leukaemia (ALL) the bone marrow makes large numbers of abnormal immature lymphocytes called lymphoblasts. There are various sub-types of ALL. For example, the abnormal lymphoblasts can be immature B or T lymphocytes. ALL can occur at any age, but about 6 in 10 cases occur in children. It is the most common form of leukaemia to affect children.

Acute myeloid leukaemia

In acute myeloid leukaemia (AML) the bone marrow makes large numbers of abnormal immature white blood cells which are derived from a myeloid stem cell. The abnormal immature cells are called blasts. There are various sub-types of AML, depending on exactly what cell type becomes cancerous and at what stage in the maturing process. AML is an uncommon disease. Most cases occur in people aged over 50.

Chronic lymphocytic leukaemia

In chronic lymphocytic leukaemia (CLL) you have many abnormal B lymphocytes. Typically, CLL develops and progresses very slowly - over months or years, even without treatment.

Chronic myeloid leukaemia

Chronic myeloid leukaemia (CML) develops due to a problem with a stem cell in the bone marrow which becomes abnormal. The abnormal stem cell multiplies and the cells that are made from the abnormal stem cells mature and develop into near normal white cells - mainly neutrophils, basophils and eosinophils (collectively called granulocytes). Typically, CML develops and progresses slowly - over months or years, even without treatment.

What causes leukaemia?

A leukaemia is thought to start first from one abnormal cell. What seems to happen is that certain vital genes which control how cells divide, multiply and die, are damaged or altered. In most cases of leukaemia, the reason why a cell becomes abnormal is not known. There are certain 'risk factors':

  • Radiation.
  • Past treatment with chemotherapy or other drugs that weaken the immune system.
  • Certain genetic disorders, the most common being Down's syndrome.
  • Exposure to certain chemicals such as benzene.

What are the main symptoms of leukaemia?

  • Anaemia.
  • Blood clotting problems.
  • Serious infections.
  • Other symptoms which may develop include: pain in the bones or joints (mainly with ALL), persistent fever and weight loss.

How is leukaemia diagnosed and assessed?

A blood test
A bone marrow sample
Cell and chromosome analysis
Lumbar puncture
This test collects a small amount of fluid from around the spinal cord - cerebrospinal fluid (CSF).  By examining the fluid for leukaemia cells, it helps to to find out if the leukaemia has spread to the brain and spinal cord. This is mainly done when assessing ALL and sometimes AML.
Various other tests
A chest X-ray, blood tests and other tests are usually done to assess your general wellbeing.

What is the treatment for leukaemia?

The treatment advised depends on the exact type of leukaemia, and the stage it is at. For example, ALL is usually treated as soon as possible with intensive chemotherapy. On the other hand, people in the early stages of CLL may not need any treatment.

What is the outlook (prognosis)?

The outlook varies for each of the different leukaemias. However, the overall outlook may be better than many people imagine. For example, the outlook for ALL has greatly improved over the last 20 years or so. Most children with ALL (about 7-8 in 10 cases) can be cured. Also, the chronic leukaemias (CLL and CML) often progress slowly - often over several years. Even in those cases which are not cured, treatment with chemotherapy and other treatments can often prolong survival for quite some time.

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