IKZF1 and inborn error of immunity: The key factor defining the phenotype is the protein expression of IKAROS which is dependent on the germline alterations of IKZF1 gene, and according to these genetic and proteic variations, three clinical groups are established among those primary immunodeficiencies/inborn errors of immunity patients (12): Haploinsufficiency (HI), Dimerization defective (DD) and Dominant negative (DN).