SERPING1 and hyperinsulinemic hypoglycemia, familial, 4: C1 inhibitor (C1-INH) deficiency is the most common form of HAE and is subdivided into two types: type 1 affects approximately 85% of patients and is characterized by low levels of functional C1-INH; type 2 affects approximately 15% of patients and is characterized by normal or elevated levels but reduced functional activity of C1-INH [3].