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What is hairy cell leukaemia?

There are several types of leukaemia. But doctors divide them into 2 main groups, based on the speed at which they develop:

  • acute leukaemia can develop very quickly
  • chronic leukaemia can develop over months or years without causing many symptoms

Hairy cell leukaemia (HCL) is a rare type of chronic leukaemia. It develops slowly from white cells called B lymphocytes. When doctors look at the cells under a microscope, they have hair-like outgrowths on their surfaces. This is where the name hairy cell comes from.

Although often easier to treat, it is similar to other types of chronic leukaemia in how it develops and how it affects you.

There's a rarer type of hairy cell leukaemia called hairy cell leukaemia variant (HCL-V).

The blood and blood cells

Leukaemia is a cancer of the blood forming system. Most types of leukaemia cause the bone marrow to make abnormal white blood cells. These abnormal cells can get into the bloodstream and circulate around the body. To understand the effects of any type of leukaemia it helps to know more about blood cells. 

How you make blood cells

Your body makes blood cells in the bone marrow. The bone marrow is the soft inner part of your bones. You make blood cells in a controlled way, as your body needs them.

All blood cells start as the same type of cell, called a stem cell. The stem cells then develop into:

  • myeloid stem cells become white blood cells called monocytes and neutrophils (granulocyte), red blood cells and platelets
  • lymphoid stem cells, which become white blood cells called lymphocytes

The diagram below helps to explain this.

Diagram showing how blood cells are made

White blood cells (leucocytes)

There are several different types of white cells in the blood. There are more of some types than others. They are an important part of the immune system, helping the body to fight infection. These blood cells can be made very quickly and generally have a short life. Some only live for a few hours, others for a few days.

Red blood cells (erythrocytes)

Red blood cells carry oxygen from the lungs around the body to the tissues. They give the blood its red colour.

Platelets (thrombocytes)

Platelets are very important in blood clotting. They clump together to form a plug if bleeding occurs. Then they release other chemicals that help the blood to clot and the blood vessel to be repaired.

How leukaemia might affect you

Leukaemia causes your body to make abnormal white blood cells and they don’t work properly.

Too many white blood cells can overcrowd the bone marrow. So there is not enough space for other types of blood cells. Then you might have lower than normal levels of red blood cells and platelets.

Abnormal white blood cells

The body needs normal white bloods to help fight infection.

Abnormal white blood cells make you more likely to get infections, and it is harder to get over the infections.

Abnormal white blood cells can also build up in other parts of the body, such as the spleen and lymph nodes, or the liver. This can make your tummy (abdomen) swell and feel uncomfortable. The leukaemia cells can also spread to the brain in some people.

Fewer red blood cells (anaemia)

You might feel very tired and breathless.

Fewer platelets

A low platelet count can mean you bruise or bleed more easily. 

You might have bruising, nosebleeds or bleeding gums. 

How common is it?

Hairy cell leukaemia is very rare. About 9,900 cases of leukaemia are diagnosed each year in the UK. But only around 220 of these are hairy cell leukaemia.

Last reviewed: 
28 Feb 2018
  • Statistics from Cancer Research UK's Cancer Statistics team

  • Cancer and its management (7th edition)
    J Tobias and D Hochhauser
    Wiley-Blackwell, 2015