Functional genetics in inborn errors of immunity

Inborn errors of immunity are genetic defects of the immune system, causing increased susceptibility to infection, autoinflammation, autoimmunity and immune dysregulation. Next-generation sequencing has enabled exponential identification of novel inborn errors of immunity due to mutations in genes encoding for proteins that participate in the immune response. However, genomic sequencing often yields multiple variants in potential candidate genes, hence functional validation of these genetic defects becomes paramount to achieve diagnosis and discovery. Genome-editing technologies such as CRISPR-Cas9 have allowed exponential advances on discovery of new primary immunodeficiencies, enabling appropriate diagnosis and treatment. This review summarizes the heterogeneous clinical presentation of primary immunodeficiencies and contextualizes the rationale for functional validation studies to achieve diagnosis and discovery, subsequently leading to the application of directed therapies.