Monogenetic variants known to be associated with CVID were present in three patients: an IKZF1 mutation in two IgG-responders and an NFKB1 mutation in one IgG-nonresponder; in all other CVID patients the presence of gene mutations associated with other primary immunodeficiency disorders, and also any known monogenetic cause of CVID phenotype was excluded by targeted gene sequence analysis (Illumina technology performed on a MiSeq NGS). Here, IKZF1 is linked to common variable immunodeficiency.