ICOS and common variable immunodeficiency: Genetic analysis of CVID patients has established the involvement of bi-allelic mutations in ICOS, CD19, CD20, CD21, CD80, PKCD, and LRBA. Furthermore, mono-allelic dominant mutations have been identified in PIK3CD, NFKB2, PIK3R1 NFKB1, and IKZF1 (38).