Initially, these genes include CD19 (16), CD20 (17), CD21 (18), CD81 (19), ICOS (20), TACI (21), BAFFR (22), however, recently more genes have been associated with CVID such as TWEAK, CD27, IL21, IL21R, LRBA, CTLA4, PI3KCD, IKAROS, NFKB1, NFKB2, PRKCD, PIK3R1, VAV1, RAC2, BLK, and IRF2BP2 (23–25). Here, CD27 is linked to common variable immunodeficiency.