ICOS and common variable immunodeficiency: However, with the use of genome‐wide association studies and next‐generation sequencing have delineated several gene mutations in CVID including CD19, CD20, CD21, CD81, TACI (TNFRSF13B), BAFF (TNFRSF13C), PTEN, PI3KD, PIK3R1, TWEAK, TRNT1, TTC37, NFKB1, NFKB2, IKZF1, IRF2BP, ATP6AP1, ITPKB, PRKCD, LRBA, and ICOS.13, 32, 33