It's not known what causes most cases of leukaemia. However, there are many risk factors that are known to increase your chances of getting chronic lymphocytic leukaemia.

Risk factors for chronic lymphocytic leukaemia include:

• having a family history of the condition
• being of European, American or Australian origin
• having certain medical conditions
• being male 

These are discussed in more detail below.

Family history

In some cases, chronic lymphocytic leukaemia appears to run in families. It's thought that an inherited gene mutation (change to a gene) could increase your susceptibility to developing the condition. This means there may be certain genes in your family that make it more likely that you'll develop chronic lymphocytic leukaemia.

More research is needed, but having a parent or sibling (brother or sister) with chronic lymphocytic leukaemia slightly increases your chances of also developing the condition.

Ethnicity

Chronic lymphocytic leukaemia most commonly affects people of European, American and Australian origin.

It's rare in people from China, Japan and South East Asia, and it affects more white people than black people. It's not known why the condition affects people of some ethnic backgrounds and not others.

Other medical conditions

Research has shown that having certain medical conditions slightly increases your chances of developing chronic lymphocytic leukaemia. These conditions include:

• pneumonia (chest infection) 
• sinusitis 
• shingles 
• autoimmune haemolytic anaemia
• long-term (chronic) osteoarthritis
• prostatitis (an inflamed prostate)

However, rather than causing chronic lymphocytic leukaemia, some of these conditions may occur as a result of having lowered immunity during the early stages of the condition.

Having a lowered immunity due to having a condition such as HIV or AIDS, or taking immunity lowering medication following an organ transplant can also increase your risk of developing chronic lymphocytic leukaemia.

Radiation exposure

Exposure to radiation is known to increase the risk of getting other types of leukaemia, but it's not been linked specifically to chronic lymphocytic leukaemia.

The Cancer Research UK website has more information about the risk factors for chronic lymphocytic leukaemia.

Sex and age

For reasons that are unclear, men are around twice as likely to develop chronic lymphocytic leukaemia than women. The risk of developing leukaemia also increases as you get older.