Chronic myeloid leukaemia begins with an alteration to the structure of the DNA found in the stem cells responsible for producing white blood cells. This is known as a genetic mutation.
The DNA provides the cells with a basic set of instructions, such as when to grow and reproduce. The mutation in the DNA changes these instructions so that stem cells produce more white blood cells than are needed.
The white blood cells are also produced when they are still immature, so they do not have the infection-fighting properties of healthy ‘adult’ white blood cells.
Eventually, as the number of immature cells (blast cells) increases, it leads to a corresponding decrease in red blood cells and platelets. This reduction in other types of healthy blood cells causes many of the symptoms of chronic leukaemia.
Possible triggers for chronic leukaemia
What triggers the development of chronic leukaemia and causes the initial mutation in stem cells is unknown. The one proven risk factor is exposure to radiation.
However, radiation is only a significant risk if the levels are extremely high, such as those recorded after an atomic bomb explodes, or those released after a nuclear reactor accident, such as the one at Chernobyl.
Benzene
There is limited evidence that prolonged exposure to the chemical benzene leads to an increased risk of chronic myeloid leukaemia. Benzene is found in petrol and is also used in the rubber industry, but there are strict controls to protect people from prolonged exposure.
Benzene is also found in cigarettes. However, it is thought that smoking is more of a risk factor in acute leukaemia than it is in chronic leukaemia.
Occupational risks
A number of occupations have been linked to an increase risk of chronic leukaemia, possibly due to exposure to certain substances such as pesticides or chemicals.
These occupations include:
- all types of agricultural workers
- people who are involved with rubber or plastic manufacture
- tailors and dressmakers
- cleaners
- builder’s labourer
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Overview - Causes of chronic myeloid leukaemia
