Unlike for APDS1 and 2 where more than 50 patients per defect have been described [19–29,35–44], fewer patients have been shown to suffer from autosomal recessive p110δ deficiency (2 kindreds) [30–32], p85α deficiency (3 patients) [45, 46], or PIK3CG deficiency (2 patients) [33, 34]. Here, PIK3CG is linked to hyperinsulinemic hypoglycemia, familial, 4.