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What is leukaemia?

Leukaemia is cancer of the white blood cells, which begins in the bone marrow.

It starts when the body makes too many immature white blood cells (blast cells). These abnormal blast cells are known as leukaemia cells. They multiply out of control and continue to divide but never mature into normal cells.

Because the leukaemia cells are immature and abnormal, they don’t carry out the usual infection-fighting function of white blood cells. They also crowd out normal white blood cells, which then can’t work properly. This increases the risk of infections. When the bone marrow fills with leukaemia cells, there is little room for healthy red cells and platelets to be produced.

Leukaemia’s are grouped in two ways: the type of white blood cell affected – lymphoid or myeloid; and how quickly the disease develops and gets worse. Acute leukaemia appears suddenly and grows quickly while chronic leukaemia appears gradually and develops slowly over months to years.

This information refers to four types of leukaemia:

Acute Lymphoblastic Leukaemia (ALL)

Normal lymphocytes fight infection. When you have acute lymphocytic leukaemia, the lymphocytes can’t function properly, and you may develop a serious infection. The disease also causes many abnormal lymphocytes to be produced, crowding out the normal red blood cells and platelets.

Acute lymphocytic leukaemia is most common in children. However some adults develop this type of leukaemia. About 370 people are diagnosed each year.

This is sometimes called ‘lymphoblastic’ leukaemia.

Chronic Lymphoblastic Leukaemia (CLL)

This leukaemia also affects the lymphocytes, but usually develops much more slowly than acute lymphocytic leukaemia.

The disease progresses slowly, so the normal cells aren’t crowded out as rapidly as in the acute type of the disease. If you have chronic lymphocytic leukaemia, you may not feel any symptoms until the later stages of the disease. In some cases, symptoms never occur because the disease progresses so slowly.

This disease affects adults and doesn’t occur in children. CLL is the most common type of chronic leukaemia, with about 1600 people diagnosed each year.

Acute Myeloid Leukaemia (AML)

This is the most common type of acute leukaemia in adults, with about 1050 people diagnosed each year.

Acute myeloid leukaemia mainly affects the myeloid cells known as granulocytes, but also red blood cells, platelets and monocytes. The disease creates too many young myeloid cells and not enough mature myeloid cells. The young myeloid cells can block blood vessels.

Chronic Myeloid Leukaemia (CML).

Chronic myeloid leukaemia can occur at any age, but is uncommon below the age of 20 years.

Too many myeloid cells are present. Chronic myeloid leukaemia occurs in two stages: first, there’s a slow multiplication of abnormal cells. Then, it can quickly change into an acute stage. About 320 people are diagnosed with CML annually.

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This information is reviewed by

This information was written and last reviewed in September 2020 by Cancer Council SA's experienced information team with support from national Cancer Council publications.