**1. Introduction**

Hereditary angioedema (HAE) is a rare disease, clinically characterized by recurrent unpredict‐ able nonpitting and nonpruritic swelling episodes involving different mucosal or cutaneous surfaces of the body such as the larynx, face, extremities, gastrointestinal tract, and urogenital area [1]. In the late 1880s, Osler described the hereditary feature of angioedema for the first time [2]. In the 1960s, a deficiency in a type of serine proteinase inhibitor, C1 esterase inhibi‐ tor (C1‐inh), was discovered as the cause of HAE, and a few years later, the second form was

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defined as non‐functioning C1‐inh. These diseases are called type I and type II HAE, respec‐ tively [3, 4]. These laboratory abnormalities in C1‐inh are the result of the mutations found in the C1‐inh gene called SERPING1 [5]. In the 2000s, a third form of HAE was defined and in these patients characteristic clinical signs and symptoms are seen; however, the level and the function of C1‐inh are normal with no mutations on the SERPING1 gene [6, 7]. However, mutations in the F12 gene were found in approximately 25% of these patients. A strong asso‐ ciation between this type of HAE and conditions causing increased levels of estrogen such as pregnancy and the usage of oral contraceptives was determined [7, 8]. Therefore, at first, this type was called estrogen‐dependent or type III hereditary angioedema [6]. After affected male relatives were reported, it was renamed as hereditary angioedema with normal C1‐inh [9].

HAE is rarely seen, and its estimated prevalence ranges from 1:30,000 to 1:80,000 in the gen‐ eral population [10]. The most common form of HAE is the first type, which is responsible for 85% of the patients [10]. HAE is an autosomal dominant disease generally affecting all generations in a family, although a quarter of patients do not have a family history. Patients are similarly affected independent of gender and ethnicity [11]. Mortality rates range from 14 to 33% mostly because of poorly treated laryngeal episodes, which indicates the significance of early diagnosis and appropriate management [12, 13].
