SERPING1 and hereditary angioedema: The defect of C1INH comprises either a deficiency (type I C1INH-HAE) or a dysfunction (type II C1INH-HAE) of the protein, allowing for a dysregulated plasma kallikrein activity within the kallikrein–kinin pathway, and thus for the overproduction of bradykinin with, in turn, the consequent activation of the bradykinin B2 receptors (1, 2).