Normally, excess BK production is regulated by several mechanisms, including (1) the production of functional C1-INH (abnormal in patients with HAE-C1INH), which limits the generation of BK from HK, and (2) conversion of BK to its inactive compounds by angiotensin-converting enzyme (ACE) and aminopeptidase-P (AP-P).6 This evidence concerns the gene SERPING1 and hereditary angioedema.