['This study reports the identification of a novel heterozygous IKBA missense mutation (p.M37K) in a boy presenting with ectodermal dysplasia with immunodeficiency (EDA-ID) who had wild type IKBKG gene encoding NEMO. Our aim was to characterize the clinical course of this IκB-α gain-of-function mutant and to investigate if the p.M37K substitution affects NF-κB activation by interfering with IκB-α degradation, thus impairing NF-κB signaling and causing the EDA-ID phenotype.', 'NF-κB signaling was evaluated by measuring IκB-α degradation in patient fibroblasts. In addition, transiently transfected HeLa cells expressing either the M37K-mutant IκB-α allele, the previously characterized S36A-mutant IκB-α allele, or wild type IκB-α were evaluated for IκB-α degradation and NF-κB nuclear translocation following stimulation with TNF-α.', 'Clinical findings revealed a classical ectodermal dysplasia phenotype complicated by recurrent mucocutaneous candidiasis, hypothyroidism, hypopituitarism, and profound combined immunodeficiency with decreased numbers of IL-17 T cells. IκB-α degradation after TNF-α and TLR agonist stimulation was abolished in patient fibroblasts as well as in HeLa cells expressing M37K-IκB-α similar to cells expressing S36A-IκB-α resulting in impaired nuclear translocation of NF-κB and reduced NF-κB dependent luciferase activity compared to cells expressing wild type IκB-α. Patient whole blood cells failed to secrete IL-6 in response to IL-1ß, Pam2CSK4, showed reduced responses to LPS and PMA/Ionomycin, and lacked IL-10 production in response to TNF-α.'] Does a novel gain-of-function IKBA mutation underlie ectodermal dysplasia with immunodeficiency and polyendocrinopathy?