ANGPT1 impairment is associated with angioedema, and ANGPT1 variants can be the basis of HAE.

IntroductionHereditary angioedema due to C1-inhibitor deficiency (C1-INH-HAE type I) or dysfunction (C1-INH-HAE type II) is a rare disease characterized by recurrent episodes of edema with an estimated frequency of 1:50,000 in the global population without racial or gender differences. In this study we present the results of a nationwide survey of C1-INH-HAE patients referring to 17 Italian centers, the Italian network for C1-INH-HAE, ITACA.MethodsItalian patients diagnosed with C1-INH-HAE from 1973 to 2013 were included in the study. Diagnosis of C1-INH-HAE was based on family and/or personal history of recurrent angioedema without urticaria and on antigenic and/or functional C1-INH deficiency.Results983 patients (53% female) from 376 unrelated families were included in this survey. Since 1973, 63 (6%) patients diagnosed with C1-INH-HAE died and data from 3 patients were missing when analysis was performed. Accordingly, the minimum prevalence of HAE in Italy in 2013 is 920:59,394,000 inhabitants, equivalent to 1:64,935. Compared to the general population, patients are less represented in the early and late decades of life: men start reducing after the 5th decade and women after the 6th. Median age of patients is 45 (IQ 28-57), median age at diagnosis is 26 years (IQ 13-41). C1-INH-HAE type 1 are 87%, with median age at diagnosis of 25 (13-40); type 2 are 13% with median age at diagnosis of 31 (IQ 16-49). Functional C1INH is ≤50% in 99% of patients. Antigen C1INH is ≤50% in 99% of type 1. C4 is ≤50% in 96% of patients. The chance of having C1-INH-HAE with C4 plasma levels >50% is < 0.05.ConclusionThis nationwide survey of C1-INH-HAE provides for Italy a prevalence of 1:64,935. C1-INH-HAE patients listed in our database have a shorter life expectancy than the general population. An increased awareness of the disease is needed to reduce this discrepancy. Measurement of C4 antigen can exclude diagnosis of C1-INH-HAE with an accuracy > 95%. This parameter should be therefore considered for initial screening in differential diagnosis of angioedema.

We hypothesize that VEGFs and Angs induce a state of 'vascular preconditioning' that may predispose to angioedema attacks. In addition, the identification of increased plasma levels of VEGFs and Angs in patients with C1-INH-HAE may prompt the investigation of VEGFs and Angs as biomarkers of C1-INH-HAE severity.

Recurrent angioedema (AE) without wheals is increasingly recognized as a clinical entity and a frequent cause of admission to the emergency room. The Hereditary Angioedema Working Group (HAWK) classification allowed the scientific community to go beyond the semantic confusion that dominated this topic for decades. This classification distinguishes hereditary and acquired forms of AE, either related or unrelated to C1 inhibitor deficiency. Recently, additional mechanisms have been involved in the AE pathogenesis, including the uncontrolled activation of factor XII, generation of vasoactive mediators that induce dysregulation of endothelial functions, and bidirectional interactions between mast cell-derived mediators and the plasma contact system. Thus, recurrent AE can be determined by multiple and concurrent mechanisms that may generate distinct clinical phenotypes of the disease. Frequency, severity, and the location of attacks are quite different from patient to patient and, even in the same patient, they may change throughout the course of life. The severity of the clinical phenotype strongly influences the burden of the disease and patients’ quality of life. Despite major advances in our understanding of recurrent AE, many unsolved questions remain, leaving several unmet needs for patients and caregivers. This review is focused on a description of different AE phenotypes and the concurrent mechanisms leading to their pathogenesis. A better definition of cellular and molecular pathways responsible for the distinct AE phenotypes may help to improve diagnosis and may lead to a personalized approach to prophylaxis and treatment of the disease.

Hereditary angioedema (HAE) is becoming much more genetically complex than was initially considered. Thus, the role of HAE genetics is expanding beyond research laboratories and the genotyping of subjects suffering from HAE has become diagnostically indispensable in clinical practice. The synthesis and interpretation of the clinical and biochemical analyses to facilitate appropriate genetic test selection has thus also become significantly more complex. With this in mind, an international multidisciplinary group of 13 experts in HAE genetics and disease management was convened in October 2018. The objective was to develop clear, actionable, evidence-and consensus-based statements aiming to facilitate the communication between physicians treating HAE patients and clinical geneticists, and thus promote the effective use of genetics in the management of the disease. Eleven consensus statements were generated, encompassing considerations regarding the clinical indications for genotyping angioedema patients, the methods of detection of HAE causative variants, the variant pathogenicity curation, the genotyping of HAE patients in the clinic, and genetic counseling. These statements are intended both to guide clinicians and to serve as a framework for future educational and further genetic testing developments as the field continues to evolve rapidly.

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Background: Hereditary angioedema (HAE) comprises HAE with C1-inhibitor deficiency (C1-INH-HAE) and HAE with normal C1-INH activity (nl-C1-INH-HAE), due to mutations in factor XII (FXII-HAE), plasminogen (PLG-HAE), angiopoietin 1 (ANGPT1-HAE), kininogen 1 genes (KNG1-HAE), or angioedema of unknown origin (U-HAE). The Italian network for C1-INH-HAE (ITACA) created a registry including different forms of angioedema without wheals. Objective: We analyzed clinical and laboratory features of a cohort of Italian subjects with nl-C1-INH-HAE followed by ITACA to identify specific biomarkers. Methods: A total of 105 nl-C1-INH-HAE patients were studied. Plasma concentrations of cleaved high-molecular-weight kininogen (cHK), vascular endothelial growth factors (VEGFs), angiopoietins (Angs), and secreted phospholipase A 2 enzymes (sPLA 2 ) were evaluated. Results:We identified 43 FXII-HAE patients, 58 U-HAE, and 4 ANGPT1-HAE. We assessed a prevalence of 1:1.4 × 10 6 for FXII-HAE and 1:1.0 × 10 6 for U-HAE. cHK levels in U-HAE patients were similar to controls in plasma collected using protease inhibitors cocktail (PIC), but they significantly increased in the absence of PIC. In FXII-HAE patients, cHK levels, in the absence of PIC, were significantly higher than in controls. We found a significant increase of VEGF-A, VEGF-C, and Ang1 levels in U-HAE patients compared to controls. In FXII-HAE, only VEGF-C levels were increased. Ang2 concentrations and sPLA 2 activity were not modified. The levels of these mediators in ANGPT1-HAE patients were not altered. Conclusions:Our results suggest that pathogenesis of FXII-, ANGPT1-, and U-HAE moves through an unbalanced control of kallikrein activity, with bradykinin as most likely mediator. VEGFs and Ang1 participate in the pathophysiology of U-HAE increasing the basal vascular permeability. K E Y W O R D S angioedema, biomarkers, epidemiology, genetic | 1395 BOVA et Al.

SummaryHereditary angioedema (HAE) is an autosomal dominant disease due to mutations in the C1 inhibitor gene (C1NH) that affects protein synthesis (HAE type I) or function (HAE type II). In 45 subjects affected by HAE diagnosed through clinical features and C1 inhibitor deficiency from the south of Italy (38 with type I and 7 with type II HAE), the whole C1NH coding region was screened for mutations by direct DNA sequencing. A severity score based on clinical manifestation, age at disease onset, and need for long-term prophylaxis was used to investigate possible genotype-phenotype correlations. A series of 22 different mutations was identified: nine missense (40.9%), five nonsense (22.7%), six frameshift (27.3), one small deletion (4.5%), and one splicing defect (4.5%). Nine C1NH mutations have not been previously described. No correlation was found between C1 inhibitor function level and severity score or age at first attack. Moreover, there was no correlation between different types of mutations and clinical phenotype. The number of different mutations identified highlights the heterogeneity of C1 inhibitor deficiency and supports the hypothesis that HAE clinical phenotype is not strictly related to the type of mutation but rather depends on unknown factors.