SERPING1 and hereditary angioedema: Notably, in about 25% of patients ade novomutation occurs.55Recent guidelines recommend to test children from HAE patients as early as possible.8, 56However, the testing of neonates and infants proves difficult, since antigenic and functional C1-inhibitor levels in peripheral and cord blood of healthy children are lower than in adults.57Therefore, tests performed in infants should be repeated after the child is one year old.