NFKB1 and viral infectious disease: This review synthesizes human inborn errors of the alternative NF-κB pathway-affecting core components, upstream ligands/receptors, or regulators, or regulatory elements-highlighting their shared and distinct effects on lymphoid development, immune dysregulation, and mTEC-mediated tolerance, which can lead to impaired B and T cell function, the development of neutralizing anti-type I IFN autoantibodies, susceptibility to severe viral diseases, and syndromic features.