Risk factors and causes of non-Hodgkin lymphoma
For most people with NHL, a cause is never found. But there are factors that are known to increase the risk of developing NHL. Most people who develop NHL don’t have any of these, though.
Here are some of the known risk factors for NHL:
A weakened immune system
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When a person’s immune system doesn’t work fully, they have an increased risk of developing lymphoma. This may be the case for people taking medicines to suppress their immune system after an organ transplant, and people with medical conditions that reduce immunity, such as HIV. We have more information about HIV-related lymphoma
Several autoimmune disorders, including rheumatoid arthritis, Sjogren’s syndrome (which causes dry eyes and a dry mouth), and Hashimoto’s thyroiditis (causes inflammation of the thyroid gland) can increase the risk of developing NHL. Doctors don’t fully understand why this is. It may be due to the effects of the autoimmune condition. It may also be because some treatments for autoimmune conditions suppress the immune system. Or, it may be due to a combination of both of these things.
Previous cancer treatment
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NHL is slightly more common in people who have been treated for cancer before. Treatment with radiotherapy, or with some chemotherapy drugs, can increase a person’s risk of developing NHL many years later. However, the risk is very small compared to the benefit of having the treatment in the first place.
Being exposed to some viruses or bacteria can increase the risk of developing some types of NHL.
A stomach infection called helicobacter pylori can sometimes cause a type of lymphoma (MALT lymphoma) to develop in the stomach.
The Epstein Barr virus (EBV), which causes glandular fever, may slightly increase the risk of developing lymphoma. However, EBV is very common in the UK and very few people go on to develop NHL because of it. The risk of EBV causing NHL is highest in people who are on long-term treatment to suppress their immune system after an organ transplant.
Another virus called the Human T-cell leukaemia/lymphoma virus (HTLV-1) can cause a type of lymphoma called Adult T-cell leukaemia/lymphoma (ATLL). But, both the HTLV-1 virus and the type of lymphoma it causes are very rare in the UK.
NHL isn’t infectious and can’t be passed on to other people.
People with a close relative (brother, sister or parent) who has been diagnosed with NHL have a slightly increased risk of developing it themselves. But, in the UK the lifetime risk of developing NHL is small (1-2 people in every 100). This means that even if you have a close relative with NHL, your risk of developing it remains low. Most people who develop NHL don’t have any family members with lymphoma.