ICOS and hyperinsulinemic hypoglycemia, familial, 4: Therefore, ICOS deficiency accounts for less than 1% of approximately 2600 CVID-like patients with known gene defects (including TNFRSF13B (80%), TNFRSF13C (4%), LRBA (2.5%), and PIK3CD (2.5%)) [12–17, 19].