Acute and chronic classifications do not reflect how serious the disease is, but the rate of progression. Acute leukaemia develops and progresses rapidly, while chronic leukaemia appears gradually and is slow growing over months to years.
Due to the rapid nature of acute leukaemia treatment usually begins quickly after diagnosis. Chronic leukaemia may not require treatment for a long time after it is diagnosed.
Healthy bone marrow produces immature white blood cells, called blast cells. These blast cells then develop into mature white cells, red cells and platelets, and are eventually released into the blood stream.
In people with acute leukaemia, the diseased bone marrow produces an excessive number of abnormal blast cells, called leukaemic cells. These immature cells accumulate in the bone marrow interfering with the production of normal blood cells.
Common forms of acute leukaemia:
- Acute lymphoblastic leukaemia (ALL) – affects immature cells called lymphoblasts. This type of leukaemia develops quickly.5 Most ALL occur in children under four years of age. 5
- Acute myeloid leukaemia (AML) – affects immature cells called myeloblasts. It is the most common form of acute leukaemia in adults.6
In chronic leukaemia there is a build-up of mature but abnormal white blood cells that have undergone a malignant change when developing from a blast cell.
Common forms of chronic leukaemia are:
- Chronic lymphocytic leukaemia (CLL) – the most common type of leukaemia in western countries. Predominantly affects older people and is often very slow growing.7
- Chronic myeloid leukaemia (CML) – typically grows slowly in the early phases but can transform to acute leukaemia.3