Subsequently, various types of germline mutations in the IKZF1 gene have been identified in patients with a CVID-like phenotype, including missense mutations (all of which have been classified as pathogenic or probably pathogenic), frame-shift mutations, nonsense mutations, and intragenic deletions of IKZF1 [15,16,17,18,19,20,21,22] (Figure 3). Here, IKZF1 is linked to common variable immunodeficiency.