SERPING1 and hyperinsulinemic hypoglycemia, familial, 4: Interestingly, the contribution of the fibrinolytic system to HAE extends beyond C1-INH deficiency: in HAE patients with normal C1-INH activity and without FXII mutations (N-HAE), decreased levels of PAI-2 have been documented in a subpopulation of patients under baseline circumstances (48).