TNFRSF13B and common variable immunodeficiency: Genotype–phenotype correlations in CVID are even more conveyed by a predisposition to the disease, as exemplified by variants in Transmembrane Activator and CAML Interactor (TACI), aka tumor necrosis factor receptor superfamily member 13B (TNFRSF13B), which may not be causative for CVID but may coexist and interact synergistically with other variants showing deleterious effects.