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About primary immunodeficiency disorders (inborn errors of immunity)

Primary Immunodeficiency (PID) disorders, also known as inborn errors of immunity (IEI), are a diverse group of more than 400 potentially serious, chronic illnesses due to inherited absence or dysregulation of parts of the immune system. Symptoms often appear in childhood, but many can first occur in adult life. PID/IEI disorders can lead to reduced quality of life and life expectancy due to recurrent, chronic or severe infections, swellings, autoimmune and inflammatory problems and are a significant health burden. 

Individual PID/IEI disorders are rare, including many with only a few patients identified in the world, whilst the more common PID/IEI disorders affect between 1 in 10,000 and 1 in 1,000,000 people. However, taken together, the prevalence of PID/IEI disorders is overall estimated to be 1 in 1,000 people.

There are six main types of PID/IEI disorders that affect the immune system in different ways:

  • Predominantly antibody deficiencies e.g. common variable immunodeficiency (CVID)
  • Combined immunodeficiencies e.g. severe combined immunodeficiency (SCID)
  • Phagocytic cell deficiencies e.g. chronic granulomatous disease (CGD)
  • Immune dysregulation e.g. autoimmune lymphoproliferative syndrome (ALPS)
  • Autoinflammatory disorders e.g. familial Mediterranean fever (FMF)
  • Complement deficiencies e.g. hereditary angioedema (HAE)

Note: A published classification of conditions which cause PID/IEI disorders has been developed by the International Union of Immunological Societies (IUIS), which is regularly modified. The current version divides PID/IEI disorders into nine categories and refers to PID disorders as Inborn Errors of Immunity. 

Research and advances in therapies have resulted in improved health and a longer life for people with PID/IEI disorders. There are currently six main types of treatment options: 

  • Antibiotics
  • Immunoglobulin Replacement Therapy (IRT) - subcutaneous (SCIg) or intravenous (IVIg)
  • Immunomodulation – including biologics
  • Hereditary Angioedema (HAE) Treatments
  • Haematopoietic Stem Cell Transplantation (HSCT)
  • Gene Therapy


Because of their rarity, delays in diagnosis of PID/IEI disorders are common, which is associated with further complications and reduced survival rates.

For infants and very young children with severe PID/IEI disorders, diagnostic delay leads to severe complications due to infections and early death. Early diagnosis is vital to allow curative treatment such as urgent haematopoietic stem cell transplantation (HSCT), also known as bone marrow transplant (BMT).

For older children and adults where curative treatment is not possible, delay in diagnosis is associated with reduced life expectancy.

With targeted resources, patients with PID/IEI disorders can be spared unnecessary interventions and instead utilise available medical treatments to maximise their opportunities to lead productive and healthy lives. 

Content updated November 2021