Among identified genetic defects, mutations in transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI, TNFRSF13B) have been reported in 7–10% of Common Variable Immunodeficiency (CVID) patients and 13% of SIgAD carried at least one mutated TNFRSF13B allele [30]. Here, TNFRSF13B is linked to common variable immunodeficiency.