Risks and causes of hairy cell leukaemia

Your risk of developing cancer depends on many factors. This includes things like whether you smoke and have a healthy balanced diet. And also genetic and environmental factors. 

Anything that can increase or decrease your risk of cancer is called a risk factor. 

We don't know what causes hairy cell leukaemia. But there are some factors that may increase your risk of developing it.  

Having one or more risk factors doesn't mean that you will definitely get leukaemia. 

Risk factors for hairy cell leukaemia

Risk factors include:


Hairy cell leukaemia is rarely diagnosed in adults under the age of 30. It is hardly ever diagnosed in children.


Hairy cell leukaemia is more common in men than women. About 4 times as many men are diagnosed than women. 


Hairy cell leukaemia is seen more often in White people compared with Black people and Asian people. 

Family history

Your risk is slightly higher if you have a close relative (parent, sibling, child) diagnosed with hairy cell leukaemia. But most people with a family history of hairy cell leukaemia do not develop it themselves and the risk remains very low.

Other possible causes

There are often stories about potential causes in the media. It isn’t always clear which ideas are supported by evidence. There might be things you have heard of that we haven’t included here. This is because either there is no evidence about them or it is less clear.

Last reviewed: 
20 Oct 2021
Next review due: 
20 Oct 2024
  • Hairy cell leukaemia: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up
    T Robak and others on behalf of the ESMO Guidelines Committee
    Annals of Oncology, 2015. Volume 26, supplement, v100–v107

  • Pan-London Haemato-Oncology Clinical Guidelines Lymphoid Malignancies Part 5: Less Common Lymphoid Malignancies
    London Cancer Alliance (LCA), 2020

  • Guideline for the diagnosis and management of hairy cell leukaemia (HCL) and hairy cell variant (HCL-V)
    N Parry Jones and others
    British Journal of Haematology 2020, Volume 191, pages 730 - 737

  • Haematological Malignancy Research Network
    Accessed July 2021

  • Hairy cell leukemia: present and future directions
    R Kreitman
    Leuk Lymphoma. 2019 December. Volume 60, issue 12, pages 2869–2879

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