SERPING1 and hyperinsulinemic hypoglycemia, familial, 4: Hereditary angioedema due to C1-inhibitor (C1-INH) deficiency (HAE-C1-INH) can produce excess bradykinin in the kallikrein–kinin system, unpredictably and recurrently inducing acute subcutaneous and/or submucosal angioedema [1–3].