Primary Immunodeficiency Diseases (PIDs)
PIDs are a group of disorders mostly caused by defects in the genes that control the immune system. PIDs can be inherited and can therefore be passed down through families.1
People with PIDs may be more prone to infection, cancer or autoimmune disease (when the immune system attacks the body it is meant to protect).1,3
Over 300 genetic defects are known to cause PIDs.1
Some PIDs:
- May affect only a single part of the immune system or multiple cells and proteins may be impacted.
- Have only mild symptoms and require minimal or no treatment, others may result in severe repeated infections that require hospitalisation for treatment.1
Common types of Primary Immunodeficiency Diseases
- Common Variable Immune Deficiency (CVID)
- X-linked Agammaglobulinaemia (XLA)
- Selective IgA Deficiency
- IgG Subclass Deficiency
- Wiskott-Aldrich Syndrome (WAS)
- Severe Combined Immunodeficiency (SCID)
- Hyper-IgM Syndromes (HIgM)
CVID
Common Variable Immune Deficiency (CVID) is one of the most frequently diagnosed primary immunodeficiencies (PIDs).1,2
CVID can differ from person to person with respect to the level and type of antibody deficiency and the types of antibodies that are deficient. This means that, the severity of symptoms and the time the symptoms first begin can differ from person to person, which is why the condition is called common “variable” immune deficiency.1
The exact cause of CVID is not known in most cases. Although CVID may be first diagnosed during early childhood and adolescence, most cases are not diagnosed until adulthood (between the ages 20-40 years).1-3
XLA
X-linked Agammaglobulinaemia (XLA) is an inherited immunodeficiency disease in which people lack mature B-cells (the cells responsible for producing antibodies).1
XLA is a genetic disorder linked to a defect in the X chromosome. Only males are affected.1
People with XLA usually develop recurrent infections of the middle ear (otitis), sinuses (sinusitis) and lungs (pneumonia or bronchitis). In some cases, infections may move into the bloodstream and spread to other organs such as the bones, joints or brain.1
IgA
Selective IgA Deficiency is one of the most common PIDs. People with selective IgA deficiency have undetectable levels of immunoglobulin A (IgA), but usually have normal amounts of the other types of immunoglobulins.1
Most people with selective IgA deficiency appear healthy, or have relatively mild illnesses. There are, however, some people who develop serious illnesses. It is not known why some people with IgA deficiency have almost no illness, while others are very sick.1
IgG
Immunoglobulins make up the antibodies that fight infection.1
People with any type of IgG subclass deficiency may suffer from recurrent ear and/or sinus infections, but bronchitis and pneumonia may also occur.1
WAS
Wiskott-Aldrich syndrome (WAS) is a condition in which people have abnormal bleeding as well as an immune deficiency.1
WAS is a genetic disorder linked to the X chromosome. Only males are affected.1
SCID
Severe combined immunodeficiency (SCID) is a rare and potentially fatal primary immunodeficiency usually identified in babies. SCID is generally considered to be the most serious of the primary immunodeficiencies. There are at least 13 different genetic defects that can cause SCID.1,2
Children with SCID may develop serious infections caused by organisms that are usually not harmful in children who have normal immunity.1,2
IgM
People with Hyper-IgM (HIGM) syndrome have low levels of immunoglobulin G (IgG) and IgA in the blood but have normal or high levels of IgM.
A number of different genetic defects can cause HIGM syndrome. Most people with HIGM syndrome develop symptoms during their first or second year of life.
The most common problem in all forms of HIGM syndrome is an increased risk of recurrent upper and lower respiratory tract infections.1
This is not a complete list of all PIDs.
It is important to speak to your doctor if you are concerned that you, or a family member, may have a PID or if you would like more information about a PID that you or a family member has been diagnosed with.
Secondary Immunodeficiency Diseases (SIDs)
SIDs are disorders of the immune system that are caused by another disease or illness, by certain types of medications, or by some infections.1,2
Like PIDs, SIDs can make people more prone to infection, cancer or autoimmune disease. SIDs are more common than PIDs, and can develop as people age.
In some SIDs, if the cause of the deficiency is found and corrected, the function of the immune system may be improved or fixed.1
Some possible causes of SIDS1,2
- Certain cancers that affect your bone marrow such as chronic lymphocytic leukaemia (CLL), multiple myeloma (MM) or lymphoma
- Certain viruses such as human immunodeficiency virus (HIV)
- Certain medicines can disrupt your immune system, such as some chemotherapy medicines or immunosuppressive medicines (used in people who receive an organ transplant, or to treat autoimmune diseases or cancers)
- Immune Deficiency Foundation. Patient & Family Handbook for Primary Immunodeficiency Diseases. 6th Edition. Available at: https://primaryimmune.org/publication/patients-and-families/idf-patient-family-handbook-primary-immunodeficiency-diseases-6th Last Accessed: July 2024.
- ASCIA. Primary immunodeficiencies (PID) Clinical Update 2017. Available at: https://www.allergy.org.au/health-professionals/papers/pid. Last Accessed: July 2024.
- ASCIA Information for Patients, Consumers and Carers. Primary Immunodeficiencies (PID). 2015. Available at: https://www.allergy.org.au/patients/immunodeficiencies/primary-immunodeficiency Last Accessed: July 2024.