According to a population-based screening test using blood donor samples collected at Osaka (Japan), the incidence of C9 deficiency was about 0.095%, accounting for most common complement deficiency in Japan.[26] C7 deficiency is known to be the second most common type among complement deficiencies (0.0041%).[25]. This evidence concerns the gene C7 and hyperinsulinemic hypoglycemia, familial, 4.