KLK4 and hereditary angioedema: HAE, due to C1 inhibitor (C1INH) deficiency (HAE-C1INH), is a rare autosomal dominant and potentially life-threatening disease, clinically characterized by swelling attacks of the subcutaneous (SC) tissue and mucous membranes due to dysregulation of the plasma kallikrein-kinin system with enhanced generation of bradykinin [62].