ICOS and common variable immunodeficiency: The OMIM database4 includes known variants originating CVID in 13 genes: ICOS, TNFRSF13B, TNFRSF13C, CD19, CR2, MS4A1, CD81, IL21, LRBA, NFKB1, NFKB2, PRKCD, and IKZF1. There is also evidence that defects in other genes (CTLA4, PLCG2) can cause a similar phenotype or modify the severity of the disease with comorbidities (MSH5).