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Chronic lymphocytic leukaemia (CLL) is the most common type of leukaemia|. About 2,700 people in the UK are diagnosed with it each year.
CLL usually develops very slowly and many people don’t need treatment for months or years. However, some people need to have treatment straight away.
In people with CLL, the body makes too many white blood cells called lymphocytes. When examined under a microscope, the lymphocytes look normal, but they aren’t fully developed (immature) and don’t work properly. Over time, these abnormal lymphocytes build up in the lymphatic system (see below) and may cause large, swollen lymph nodes. They may also fill the bone marrow (see below), reducing the number of normal white blood cells, red blood cells and platelets that can be made.
To help you understand CLL and its treatment, it’s useful to know a little bit about your blood, how it’s made and what it does. We’ve explained more about this on this page.
Blood is made in the bone marrow. This is a spongy material that’s found in the middle of your bones, particularly in your pelvis and backbone (spine). All blood cells are made from stem cells. The bone marrow is a safe place for the stem cells to divide and grow into fully developed (mature) red blood cells, white blood cells and platelets.
These are then released into your blood to carry out different functions:
The levels of these cells in your blood are measured in a blood test called a full blood count (FBC). The figures below are a guide to the levels usually found in a healthy person.
Levels found in a healthy person
These figures can vary from hospital to hospital. They can also be slightly different in people of African-Caribbean and Middle Eastern origin. Your doctor or nurse will be able to tell you what figures they use.
The figures might look complicated when they’re written down, but in practice they’re used in a straightforward way. For example, you’ll hear doctors or nurses saying things like ‘your haemoglobin is 14’ or ‘your neutrophils are 4’. Many people with CLL soon get used to these figures and what they mean.
Your doctors will often look at the way your blood test results change over time (trend) to decide what, if any, treatment is needed.
People with CLL make too many lymphocytes (a type of white blood cell). Normally, lymphocytes are an important part of the body’s defence against bugs such as bacteria, fungal infections and viruses. They fight infections in several ways:
Lymphocytes travel around the body in the blood and the lymphatic system.
The lymphatic system is part of the immune system - the body’s natural defence against infection and disease. It’s made up of organs such as the bone marrow, thymus, spleen and lymph nodes. The lymph nodes, which are found throughout the body, are connected by a network of tiny lymphatic tubes (ducts). Lymph nodes can be felt in the neck, armpit and groin. There are also lymph nodes in the chest and the tummy (abdomen).
The lymphatic system has two main roles: it helps to protect the body from infection and it drains fluid from the body’s tissues.
The lymphatic system
View a large copy of the diagram of the lymphatic system|
Content last reviewed: 1 January 2013
Next planned review: 2015
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© Macmillan Cancer Support 2013
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