The basics

PIDs stands for primary immunodeficiencies or primary immune deficiencies. These are a group of over 450 different conditions that affect how the body’s immune system works.

People affected by PIDs have parts of their immune systems missing or not working. This leaves them with reduced or no natural defence against germs such as bacteria, fungi and viruses, which surround us every day. The consequences are that people with PIDs get infections more often than is normal; they can take longer to get better when they have antibiotic treatment and even then the infections can keep coming back.

This susceptibility to infection is one of the most common symptoms of PIDs. Often PIDs are diagnosed early in a child’s life. However, signs of immunodeficiency can also occur in older children, teenagers or adults.

Those affected can have a wide range of symptoms ranging from mild to severe, and this depends on the type of PID the person has. For example, some people may experience recurrent colds and other respiratory ailments, while others may experience heart problems, pneumonia, skin disorders and arthritis.

PIDs are rare and this means that some people remain undiagnosed for many years, resulting in organ damage and even disability.

PIDs are caused by errors in the genes of the cells that make up the immune system. Most people with PIDs are born with the condition. PIDs are mainly genetic disorders, meaning they are inherited and can be passed on from one generation to the next.

In PIDs some of the DNA building blocks that make up the genes involved in the workings of the immune system are either not there or altered. This results in either missing or faulty genes, causing essential parts of the body’s defence against infection not to be made or work properly.

In some types of PID, for example, common variable immune deficiency and other antibody deficiencies, the link to specific faulty genes is not yet so clear-cut, but this is likely to change as the technology for the screening of genes improves and more research is done.

You certainly cannot catch a PID from those affected, and they cannot transfer their disorder to anyone else through contact.

They are called primary because of the intrinsic, built-in nature of the immune deficiency. The term is used to separate PIDs from conditions where the immune system is affected by secondary causes such as other diseases (e.g. HIV), drug treatment, chemotherapy, malnutrition or environmental exposure to toxins.

There is no connection to AIDS, which is a secondary or ‘acquired’ immunodeficiency.

The effects of a PID can be immense. For example, a baby born with severe combined immunodeficiency (SCID) might not survive more than a couple of years without isolation in a sterile environment until a bone marrow transplant can be carried out. Even for a child with a less severe disorder, prolonged periods of ill-health can disrupt schooling and social contacts.

For an adult, frequent debilitating illnesses can make it more difficult to pursue a career or enjoy family life. There can be psychological problems, too. Feeling isolated, the fear of losing one’s income, or the anguish of caring for a sick child, can take its toll.

The exact figure is unknown because there isn’t a national screening programme for PIDs at birth. Similarly, people are not screened routinely during their lifetime. Usually, doctors only know if a person has an immunodeficiency when they become ill and are tested. Many people may remain undiagnosed throughout their life because they have less severe forms of primary immunodeficiency that allow them to survive and lead a relatively normal life: sadly some people may die from infection without having their underlying condition diagnosed.

Data held in PID patient registries in many countries around the world, however, is providing some estimates. In the UK over 4,500 people with PIDs have been registered on the UK Primary Immune Deficiency Registry to date. You can find out more about how you can take part in the registry here.

At present doctors estimate that about 5,000 people may be affected by a PID in the UK. Significantly this is about the same number of people with haemophilia and means that collectively PIDs are not uncommon.

Multidisciplinary teams of medical professionals look after the care of people with PIDs and are led by a consultant immunologist. Specialists are needed because the disorders are rare, they can cause severe complications and complex treatments are often needed.

It is extremely important that those affected receive expert care and advice from a consultant immunologist at one of the specialist centres in hospitals throughout the UK.

The treatment you receive will be dependent on the type of PID you have and how it affects your immune system. A large proportion of people affected by a PID have immunoglobulin replacement therapy to help keep them free from infection and are given antibiotics as and when an infection occurs. Some other types of PID may involve taking antibiotics and/or antifungal medicine daily to stave off infection. More specialised treatments and potential cures include bone marrow transplantation, enzyme replacement therapy and gene therapy.

Taking preventative measures to avoid exposure to infection also plays a key role in keeping people with a PID well.

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