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What’s the difference between Primary Immunodeficiency Disorders (PID) and Inborn Errors of Immunity (IEI)?

Recent technological and medical advances have seen a rapid increase in the discovery of genetic defects and disorders. In particular, Next Generation Sequencing (NGS) has helped researchers discover hundreds of gene defects that impact the immune system through whole exome and whole genome sequencing.

As the list of known genetic defects grows, some advocates have begun calling these conditions Inborn Errors of Immunity (IEI). But, while you may see PI, PID and IEI used interchangeably, there isn’t total consensus just yet.

A 2021 article for Frontiers in Immunology encourages thoughtful discussion around the terminology and distinction between PID and IEI.

Inborn Errors of Immunity is a more specific term that implies disorders are genetic, inherited, and transmissible to future generations. But many Primary Immunodeficiencies don’t currently have a defined genetic basis, so the term IEI doesn’t accurately represent them. For example, some patients diagnosed with Common Variable Immunodeficiency Disorder (CVID) may not have a known genetic defect.

Primary Immunodeficiency is a term that implies the disorder results in a deficient immune system, so patients are more susceptible to infections. But some patients may have primary immune defects that result in autoimmunity or immune dysregulation. In autoimmunity, the immune system attacks healthy cells, tissues and organs in the body. Meanwhile, immune dysregulation is used for an immune system with both problems.

Basically, some diseases can accurately be labelled as both PI and IEI, but that’s not the case for all of them. 

The Inborn Errors of Immunity Committee

The International Union of Immunological Societies (IUIS) is a global organization representing over 60,000 immunologists across 88 national member societies and four regional federations. IUIS has several committees that further the advancement of immunology, including the Inborn Errors of Immunity Committee. The committee was previously known as the Primary Immunodeficiencies Committee and voted to rename itself in February 2017.

Every two years, the IEI Committee publishes a classification report for IEIs. Committee members also contribute to the World Health Organisation’s Essential Medicine Lists and the International Classification of Diseases (ICD) regarding IEIs.

As of June 2022, the committee has classified 485 inborn errors of immunity (IEI).

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We empower Canadians impacted by immunodeficiency disorders to live well through education, support, advocacy, community-building, and research.

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