SERPING1 and hyperinsulinemic hypoglycemia, familial, 4: Thus, early diagnosis of HAE-C1-INH is important by screening blood tests; C1-INH deficiency spontaneously activates the classical pathway in the complement system resulting in low levels of serum C4 and CH50 with a normal serum C3 level in almost all patients with HAE-C1-INH [10].