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Causes of chronic lymphocytic leukaemia

The cause of CLL isn’t known, but research is going on to find out more.

There are a number of factors that can increase the risk of developing CLL:

Age – The risk of developing CLL increases with age. Most people with CLL are over 60; it’s rare in people under the age of 40.
Gender – CLL is more common in men than women.
Family history – In about 1 in 10 cases, other people in the family also have CLL. This is known as familial CLL. If anyone else in your family has CLL, it’s important to let your specialist know. But most people who have a relative with CLL will never develop it themselves.
Ethnicity – CLL is most common in people of European origin, slightly less common in people of African origin and rare in Asian people.

CLL is not infectious and can’t be passed on to other people.

Content last reviewed: 1 July 2010

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Macmillan Cancer Support, registered charity in England and Wales (261017), Scotland (SC039907) and the Isle of Man (604). A company limited by guarantee, registered in England and Wales company number 2400969. Isle of Man company number 4694F. Registered office: 89 Albert Embankment, London SE1 7UQ.