1. Introduction

Hereditary angioedema due to C1-inhibitor deficiency (C1-INH-HAE) is a genetic autosomal dominant disease characterized by a deficiency of the functionally active C1 esterase inhibitor (C1-INH) protein [1]. This deficiency results in an excess of bradykinin (BK), which increases vascular permeability and produces angioedema (AE) [1].

The minimum prevalence of C1-INH-HAE is 1.09 per 100,000 inhabitants in Spain [2], 1.41 per 100,000 inhabitants in Denmark [3], 1.54 per 100,000 inhabitants in Italy [4] and 1.75 per 100,000 inhabitants in Norway [5].

Other forms of BK-mediated AE are: acquired angioedema due to C1-INH deficiency (C1-INH-AAE), hereditary angioedema with normal C1-INH (C1-INH-nC1-INH), with/without mutation in the F12 gene that encodes Factor XII coagulation (HAE-FXII/HAE-D) and acquired angioedema associated with angiotensin converting enzyme inhibitors (ACEi) (AAE-ACEi). ACEis are drugs that inhibit the metabolic pathways of BK and thus produce an increase in BK. Other drugs that inhibit BK catabolism have been implicated in the development of AE. These include dipeptidyl peptidase IV (DPPIV) inhibitors, aminopeptidase P (APP) inhibitors, neutral endopeptidase (NEP) inhibitors and others. In this chapter, we will focus on C1-INH-HAE.
