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Most people who suffer from frequent infections have a completely normal immune system. However, a small number of children and adults have an abnormality of their immune system which makes them more prone to infection.  These abnormalities can be present from birth and cause infections from a young age. However, most people with immunodeficiency do not develop significant symptoms until their teens or twenties, or even later in life. This is called “Primary Immunodeficiency (PID)” since there is no other cause for the weakened immune system.

Where immunodeficiency is caused by another condition or medical treatment (e.g. treatment for cancer, or a leukaemia), it is called “Secondary Immunodeficiency (SID)”.

What is immunodeficiency?

Your immune system is a network of organs, cells and chemicals throughout your body that helps to protect you from infections. Someone who has an immunodeficiency is missing a part of their immune system. This will usually result in repeated infections, or infections might take longer to get better and need more courses of antibiotics. Autoimmune conditions and other types of inflammation may also occur in immunodeficiency.

Because immunodeficiency is rare, people often have many years of infections before the diagnosis is even considered. Immunodeficiency disorders sometimes run in families. Genetic testing is identifying an increasing number of genetic mutations (“spelling mistakes” in the genetic code) that cause immunodeficiency, but for many patients the cause of their immunodeficiency is still unknown.

Below are a number of resources about Immunodeficiency and guidance for patients and carers.

Last reviewed: 19 May 2023