HCL happens when lymphocytes (a white blood cell) become abnormal and can’t fight infections properly.  It can also affect the number of normal healthy blood cells you produce, which can lead to problems such as anaemia, bleeding and bruising, and problems with your spleen.

Hairy cell leukaemia gets its unusual name because the cells have hair-like outgowths on their surface that make them look 'hairy' when they're looked at under a microscope.

HCL is very rare - around 200 people in the UK find out they have HCL each year.

Hairy cell leukaemia is part of a group of conditions called lymphoproliferative disorders (LPDs) that also includes chronic lymphocytic leukaemia, acute lymphoblastic leukaemia and Waldenstrom macroglobulinaemia.

What causes hairy cell leukaemia (HCL)?

Almost everyone with HCL has a genetic change called BRAF that happens within the hairy cells, but not in the other cells. We don’t know the cause of these genetic changes yet. However there are some factors that we know affect how likely you are to develop HCL:

  • Age – the average age at diagnosis is between 50 - 60 years old. Children and young people don’t get HCL.
  • Sex – men are more likely than women to get HCL. Four in five people who get HCL are male
  • Genetics – almost all people with HCL have a genetic change called BRAF that happens within the hairy cells, but not in the other cells.


HCL symptoms and diagnosis

The most common symptoms of HCL include tiredness, weakness, breathing problems, palpitations, bruising and bleeding, stomach discomfort and frequent infections. Most people will have some symptoms before they're diagnosed but as HCL develops slowly, others may never notice symptoms and will be diagnosed by chance.

If your doctor thinks you might have HCL you'll have blood tests and bone marrow tests.

HCL treatment, side effects and outlook

Because HCL is a slow-developing type of leukaemia, you might not need treatment straight away. When you do need treatment, this is likely to be chemotherapy. In rare cases, some people may need an operation to have their spleen removed. Chemotherapy treatment nearly always gets rid of the leukaemia cells (this is known as remission). A remission can last for many years, but if the HCL comes back (relapse) you may need further treatment.

> Find out more in our hairy cell leukaemia (HCL) fact sheet

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