Over 450 different primary immunodeficiencies (PIDs) have been identified, with about 20 of these accounting for over 90 per cent of cases. This means that many conditions are extremely rare: indeed for some conditions, fewer than ten cases have been identified.
Classification of PIDs
Every two years an international committee of experts meets to revise and update the grouping of PID conditions according to symptoms (known as classification), adding new conditions and information on the genes that cause PID. At present, PIDs are grouped or classified under eight major subcategories based on what cells or parts of the immune system are affected.
These subcategories are:
You can download the 2021 list of known primary immunodeficiencies here.
This page was reviewed by the Chair of the Medical Advisory Panel, January 2019.