Inborn errors of immunity (IEI) comprise a heterogeneous group of disorders. The number of disorders classified as IEI has rapidly increased in recent years, driven by the expansion of the disease concept beyond susceptibility to infections and advances in genetic analysis technologies. Given that approximately 2,000 genes are involved in human immunity, additional disorders are expected to be identified in the future. To systematically organize these disorders, the International Union of Immunological Societies (IUIS) has established a classification system for IEI. In the latest IUIS classification (2024 update), 508 causative genes, 559 diseases, and 17 phenocopies are listed. Compared with the previous 2022 classification, 67 diseases and 2 phenocopies have been newly added.
The identification of new IEIs contributes not only to an increase in the number of rare diseases but also to a better understanding of the roles of these genes in human immunity. Novel insights have been revealed that could not be obtained from animal models, further deepening our understanding of human immune systems.
In this presentation, although it is not feasible to cover all newly identified disorders due to time constraints, I will provide an overview of selected IEIs that are particularly intriguing from a pathophysiological perspective, as well as those reported from Japan (including disorders likely to be identified in Japan in the future).
