Hereditary angioedema due to C1INH deficiency (HAE-C1INH) is an autosomal dominant genetic disease mediated by a dysregulated plasma kallikrein-kinin system (KKS), which generates excess bradykinin in the vascular compartment; pathophysiology that causes episodic attacks of angioedema (1). The gene discussed is KLK4; the disease is hereditary angioedema.