The pathophysiology of hereditary angioedema

Pathophysiology of bradykinin and histamine mediated angioedema

Angioedema is characterized by swelling localized to the subcutaneous and submucosal tissues. This review provides an overview of angioedema, including the different types, triggers, and underlying pathophysiologic mechanisms. Hereditary and acquired angioedema are caused by dysregulation of the complement and kinin pathways. In contrast, drug-induced and allergic angioedema involve the activation of the immune system and release of vasoactive mediators. Recent advances in the understanding of the pathophysiology of angioedema have led to the development of targeted therapies, such as monoclonal antibodies, bradykinin receptor antagonists, and complement inhibitors, which promise to improve clinical outcomes in patients with this challenging condition. To accurately diagnose and manage angioedema, an understanding of this condition's complex and varied pathophysiology is both necessary and critical.

How Does Pregnancy and Type of Delivery Affect the Clinical Course of Hereditary Angioedema?

INTRODUCTION

Knowledge on the clinical course of hereditary angioedema (HAE) during pregnancy, delivery, and breastfeeding is very limited. In this study, we aimed to evaluate the course of HAE during these periods.

METHODS

The HAE attacks C1-INH prophylaxis before and during pregnancy and during breastfeeding, and the delivery types were retrospectively determined. The severity of attacks was assessed by a 10-point Visual Analogue Scale (VAS).

RESULTS

We evaluated 88 pregnancies in 48 HAE patients among whom 20 were primiparous. Among those who had a HAE diagnosis during pregnancy (n = 34), the median attack numbers before pregnancy, during pregnancy, breastfeeding, and after breastfeeding were 17, 39, 24, and 14 (before pregnancy vs. pregnancy, p < 0.001; during pregnancy vs. breastfeeding, p = 0.001). The mean VASs (SD) were 6.59 (1.82), 8.33 (1.58), 7.32 (1.66), and 6.95 (1.90) (before pregnancy vs. pregnancy, p < 0.001; during pregnancy vs. breastfeeding, p = 0.016), respectively. Among those who received a HAE diagnosis after pregnancy (n = 54), the number (59.3%) and the severity (60%) of HAE attacks were high in pregnancy. 47 of the deliveries were normal vaginal delivery (NVD). Regional anesthesia was applied in 8 NVDs. 20 of caesarean deliveries were performed under general anesthesia, and 21 were under spinal anesthesia. Lowest numbers of attacks were found in patients who did not receive anesthesia during NVD (p = 0.001).

CONCLUSION

The course of HAE can be worse during pregnancy and breastfeeding. NVD is related to fewer HAE attacks and prophylaxis with C1-INH during NVD is not necessary to prevent a HAE attack.

[Hereditary angioedema and its new treatments: An update]

Hereditary angioedema, with or without deficient C1 inhibitor level or function, is a rare disease characterized by recurrent attacks of noninflammatory subcutaneous and/or submucosal edema. It may be life-threatening and substantially affects quality of life. Attacks may be spontaneous or induced, in a setting of emotional stress, by infections or physical trauma, in particular. As the key mediator is bradykinin, this angioedema does not respond to the usual treatments of mast cell-mediated angioedema (antihistamines, corticosteroids, adrenaline), which is much more frequent. Therapeutic management of hereditary angioedema first consists in treating severe attacks with a selective B2 bradykinin receptor antagonist or a C1 inhibitor concentrate. The latter or an attenuated androgen (danazol) can be used for short-term prophylaxis. Therapeutic solutions conventionally proposed for long-term prophylaxis (danazol, antifibrinolytics [tranexamic acid], C1 inhibitor concentrate) vary in efficacy and/or pose problems of safety or ease of use. Kallikrein inhibitors (subcutaneous lanadelumab, oral berotralstat) recently made available as disease-modifying treatment constitute an important advance in long-term prophylaxis of hereditary angioedema attacks. The advent of these new drugs is accompanied by a new ambition for patients: optimize control of the disease and thereby minimize its impact on quality of life.

The impact of puberty on the onset, frequency, location, and severity of attacks in hereditary angioedema due to C1-inhibitor deficiency: A survey from the Italian Network for Hereditary and Acquired Angioedema (ITACA)

Introduction

Hereditary angioedema due to C1-inhibitor deficiency is influenced by hormonal factors, with a more severe course of disease in women. Our study aims to deepen the impact of puberty on onset, frequency, location and severity of attacks.

Methods

Retrospective data were collected through a semi-structured questionnaire and shared by 10 Italian reference centers of the Italian Network for Hereditary and Acquired Angioedema (ITACA).

Results

The proportion of symptomatic patients increased significantly after puberty (98.2% vs 83.9%, p=0.002 in males; 96.3% vs 68,4%, p<0.001 in females); the monthly mean of acute attacks was significantly higher after puberty, and this occurred both in females (median (IQR) = 0.41(2) in the three years before puberty vs 2(2.17) in the three years after, p<0.001) and in males (1(1.92) vs 1.25(1.56) respectively, p<0.001). The increase was greater in females. No significant differences were detected in attack location before and after puberty.

Discussion

Overall, our study confirms previous reports on a more severe phenotype in the female gender. Puberty predisposes to increased numbers of angioedema attacks, in particular in female patients.

Safety of medications for hereditary angioedema during pregnancy and lactation

INTRODUCTION

Hereditary Angioedema (HAE) attacks show an increased frequency and severity for pregnant and lactating females secondary to the hormonal changes. The diagnosis and management of HAE in pregnant and lactating females pose a challenge for physicians due to the rarity of the disease and the paucity of the data for specific management.

AREAS COVERED

In this manuscript, we discuss the diagnosis and special presentation of HAE types 1 and 2 in pregnant and lactating females, including acute management, short-term prophylaxis, long-term prophylaxis, and drugs that should be avoided. Relevant publications were found through key word search of papers indexed in both Google Scholar and PubMed on 1 July 2022.

EXPERT OPINION

Treatment of HAE in the past has been mainly provided by experts; however, with more medications and an increasing number of patients, knowledge of how to care for HAE patients during pregnancy and lactation is important to review. Despite approval of additional medications in many countries, plasma-derived C1-inhibitor remains the drug of first choice for treatment in this unique population. Additional research is needed to increase safe access to other therapy options. We hope that future clinical studies, registries, and databases will shed additional light on this subject.

A Comprehensive Review of Bradykinin-Induced Angioedema Versus Histamine-Induced Angioedema in the Emergency Department

Angioedema (AE) is a condition that is frequently encountered in the emergency department (ED). It is a rare condition with localized, asymmetrical swelling of the skin and/or mucosa that is frequently nonpruritic and primarily affects locations with loose connective tissue. Physicians must have a thorough understanding of this condition since it can cause fatal airway compromise, which might be the presenting symptom. Histamine-mediated AE is the most common type of AE seen in EDs. However, ED physicians must be on the lookout for the less common bradykinin-mediated types of AE as these do not respond to the same therapy as histamine-mediated AE. Hospitals may lack specialized drugs or protocols, and many ED staff may be unable to identify or treat bradykinin-mediated AE. It is crucial to understand the pathophysiology of the various kinds of AE in order to optimize treatment. The goal of this review paper is to provide an overview of the pathophysiology, clinical manifestations, and treatment options for bradykinin and histamine-induced AE in the ED.

C1-inhibitor influence on platelet activation by thrombin receptors agonists

INTRODUCTION

Protease activated receptors 1 (PAR1) and 4 (PAR4) agonists are used to study platelet activation. Data on platelet activation are extrapolated across experimental settings. C1-inhibitor (C1INH) is a protease inhibitor present in plasma but not in isolated platelet suspensions. Here we show that C1INH affects platelet activation through PAR1 and PAR4 agonists.

METHODS

Platelets were isolated from healthy donor whole blood and then labeled with anti-CD62P and PAC1 antibodies. The platelet suspensions were exposed to PAR1 agonists SFLLRN, TFLLR and TFLLRN; PAR4 agonists AYPGKF and GYPGQV; ADP and thrombin. Flow-cytometric measurements were performed in 5, 10 and 15 min after activation.

RESULTS

0.25 mg/ml C1INH addition made platelets to faster expose CD62P and glycoprotein IIb/IIIa complex after activation with PAR1 agonists. Conversely, C1INH addition led to inhibition of platelet activation with PAR4 agonists and thrombin. Activation with ADP was not affected by C1INH.

CONCLUSIONS

Our results suggest that C1INH can modify platelet activation in the presence of synthetic PAR agonists used in platelet research. These observations may be relevant to the development of new methods to assess platelet function.

The role of C1 inhibitor and complement as acute phase reactants: are we missing the diagnosis of hereditary angioedema?

Background

C1 inhibitor (C1-INH) and complement 4 (C4) have historically been referred to as positive acute phase reactants, however this has never been evaluated in hereditary angioedema (HAE) patients. Low function of C1-INH and low levels of C4 are important in the diagnosis of HAE type 1 and 2. If C1-INH and/or C4 are significant acute phase reactants, their levels may be falsely “normal” in patients with HAE when measured during times of infection or inflammation resulting in missed or delayed diagnosis.

Case presentation

We present a case series of four HAE patients who had C4, C1-INH, c-reactive protein (CRP) and ferritin measured at baseline and again during a self-reported upper respiratory tract infection (URTI) or flu-like illness. We did not identify any HAE patients who had a significant change in their C1-INH functional level in the context of a mild infection. However, the C4 level did increase into the normal range on three occasions (2 patients, with 1 patient having elevation during two separate illnesses).

Conclusions

C1 inhibitor may not be a clinically significant acute phase protein and appears to still be a reliable diagnostic marker of hereditary angioedema, even in times of modest acute inflammation, unlike complement C4 which can be elevated in this setting.

gC1qR Antibody Can Modulate Endothelial Cell Permeability in Angioedema

Angioedema is characterized by swelling of the skin or mucous membranes. Overproduction of the vasodilator bradykinin (BK) is an important contributor to the disease pathology, which causes rapid increase in vascular permeability. BK formation on endothelial cells results from high molecular weight kininogen (HK) interacting with gC1qR, the receptor for the globular heads of C1q, the first component of the classical pathway of complement. Endothelial cells are sensitive to blood-flow-induced shear stress and it has been shown that shear stress can modulate gC1qR expression. This study aimed to determine the following: (1) how BK or angioedema patients' (HAE) plasma affected endothelial cell permeability and gC1qR expression under shear stress, and (2) if monoclonal antibody (mAb) 74.5.2, which recognizes the HK binding site on gC1qR, had an inhibitory effect in HK binding to endothelial cells. Human dermal microvascular endothelial cells (HDMECs) grown on Transwell inserts were exposed to shear stress in the presence of HAE patients' plasma. Endothelial cell permeability was measured using FITC-conjugated bovine serum albumin. gC1qR expression and HK binding to endothelial cell surface was measured using solid-phase ELISA. Cell morphology was quantified using immunofluorescence microscopy. The results demonstrated that BK at 1 µg/mL, but not HAE patients' plasma and/or shear stress, caused significant increases in HDMEC permeability. The mAb 74.5.2 could effectively inhibit HK binding to recombinant gC1qR, and reduce HAE patients' plasma-induced HDMEC permeability change. These results suggested that monoclonal antibody to gC1qR, i.e., 74.5.2, could be potentially used as an effective therapeutic reagent to prevent angioedema.

Interplay between platelets and coagulation

Haemostasis stops bleeding at the site of vascular injury and maintains the integrity of blood vessels through clot formation. This regulated physiological process consists of complex interactions between endothelial cells, platelets, von Willebrand factor and coagulation factors. Haemostasis is initiated by a damaged vessel wall, followed with a rapid adhesion, activation and aggregation of platelets to the exposed subendothelial extracellular matrix. At the same time, coagulation factors aggregate on the procoagulant surface of activated platelets to consolidate the platelet plug by forming a mesh of cross-linked fibrin. Platelets and coagulation mutually influence each other and there are strong indications that, thanks to the interplay between platelets and coagulation, haemostasis is far more effective than the two processes separately. Clinically this is relevant because impaired interaction between platelets and coagulation may result in bleeding complications, while excessive platelet-coagulation interaction induces a high thrombotic risk. In this review, platelets, coagulation factors and the complex interaction between them will be discussed in detail.

Hereditary angioedema: Pathophysiology (HAE type I, HAE type II, and HAE nC1-INH)

The pathophysiology of hereditary angioedema (HAE) in virtually all cases is the result of the uncontrolled production of the vasoactive peptide bradykinin. C1 inhibitor (C1-INH) is a serine protease inhibitor, which, under normal circumstances, is the regulator of critical enzymes that are active in the cascades that result in bradykinin generation. In the classic forms of HAE, C1-INH is not produced in sufficient quantities (<40% of normal) or the function is <40% of normal activity. The major pathway for the production of bradykinin is the "contact system," also known as the kallikrein-kinin system. This system begins with the activation of factor XII (FXII) to FXIIa, by a variety of physiologic and pathologic stimuli. FXIIa is a serine protease that binds to surfaces and cleaves prekallikrein to the active serine protease kallikrein. Kallikrein then cleaves high-molecular-weight kininogen to release the nonapeptide bradykinin. Bradykinin binds to the bradykinin β2 receptor, which increases vascular permeability and allows the flow of fluids into the extracellular space and results in angioedema. The two major enzymes generated in this cascade FXIIa and kallikrein are inhibited by C1-INH, which is the major regulator of this cascade. Failure to adequately control the production of bradykinin is thus the major mechanism for HAE. Several other types of HAE in which C1-INH is not decreased (HAE nlC1-INH) have been described. The alterations in FXII and plasminogen (also a serine protease inhibited by C1-INH) like with classic HAE are the result of dysregulation of bradykinin generation. Only genetic alterations in angiopoietin-1 may not be related to bradykinin generation, rather related to the control of the effect of bradykinin on the vascular endothelium.

Candida and Complement: New Aspects in an Old Battle

Candida is a dominant fungal pathogen in immunocompromised hosts, leading to opportunistic infections. Complement with its multifaceted functions is involved in the immune defense against this yeast, and recently several novel aspects have emerged in this old battle. It is clear that Candida can adopt both roles as a colonizer or as a pathogen. In our article, we focus on the molecular mechanisms of the Candida-complement interplay, which occur in disseminated disease as well as locally on skin or on mucous membranes in mouth and vagina; the mechanisms can be supposed to be the same. Activation of the complement system by Candida is facilitated by directly triggering the three dominant pathways, but also indirectly via the coagulation and fibrinolysis systems. The complement-mediated anti-Candida effects induced thereby clearly extend chemotaxis, opsonization, and phagocytosis, and even the membrane attack complex formed on the fungal surface plays a modulatory role, although lysis of the yeast per se cannot be induced due to the thick fungal cell wall. In order to avoid the hostile action of complement, several evasion mechanisms have evolved during co-evolution, comprising the avoidance of recognition, and destruction. The latter comes in many flavors, in particular the cleavage of complement proteins by yeast enzymes and the exploitation of regulatory proteins by recruiting them on the cell wall, such as factor H. The rationale behind that is that the fluid phase regulators on the fungal cell surface down-regulate complement locally. Interestingly, however, evasion protein knockout strains do not necessarily lead to an attenuated disease, so it is likely more complex in vivo than initially thought. The interactions between complement and non-albicans species also deserve attention, especially Candida auris, a recently identified drug-resistant species of medical importance. This is in particular worth investigating, as deciphering of these interactions may lead to alternative anti-fungal therapies directly targeting the molecular mechanisms.

Contradictory to its effects on thrombin, C1-inhibitor reduces plasmin generation in the presence of thrombomodulin

C1-inhibitor (C1INH) was shown to enhance thrombin generation (TG) in the presence of thrombomodulin (TM) by reducing production of activated protein C. Because C1INH is known to inhibit fibrinolytic system proteases, the objective of this study was to evaluate the effect of moderate (3 IU/ml) and high (16 IU/ml) C1INH concentrations on TG and plasmin generation (PG) in the presence of TM. These concentrations were evaluated based on expected maximum plasma levels following C1INH replacement therapy and recently suggested supraphysiologic dosing. TG and PG were investigated in platelet poor plasmas obtained from 21 healthy donors. An assay designed to monitor the continuous generation of the 7-amino-4-methylcoumarin fluorescence from substrates specific to thrombin or plasmin was used to evaluate the impact of C1INH activity. To characterize the C1INH effects on TG and PG, the thrombin and plasmin concentration peaks and production rates were calculated. TM addition to donor plasma shifted the concentration dependence of C1INH on TG parameters from reduction to enhancement. Conversely, PG parameters were significantly reduced by 16 IU/ml in both the presence and absence of TM. Moderate C1INH concentration (3 IU/ml) reduced TG and PG in the absence of TM but did not significantly affect these parameters in the presence of TM. Finally, 3 IU/ml of C1INH reduced PG more so than TG in the absence of TM. The presented results suggest a mechanism by which C1INH could potentiate thrombosis by inhibition of fibrinolysis.

Hereditary angioedema in children: a review and update

PURPOSE OF REVIEW

Hereditary angioedema (HAE) most often presents in the first two decades of life. Despite these patients often see multiple doctors and go many years before confirmation of the diagnosis. the impact on quality of life, productivity and risk of anxiety, depression, and posttraumatic stress emphasizes the need for early diagnosis and appropriate treatment.

RECENT FINDINGS

Over the past decade, therapy in the USA has emerged from fresh-frozen plasma and androgens to more than seven medications that are specific for bradykinin-induced disease. During the same time, treatment has evolved from intravenous to subcutaneous and the future will be a focus on oral therapy.

SUMMARY

Much optimism exists that patients with HAE will live a life with minimal disease and impact on their quality of life making it even more important to diagnose children at an early age.

Management of patients with hereditary angio-oedema in dental, oral, and maxillofacial surgery: a review

Hereditary angio-oedema (HEA) is an autosomal dominant, life-threatening genetic disorder that is caused by insufficiency or dysfunction of the C1 esterase inhibitor that develops coincidentally with recurrent oedema in the skin, internal organs, and upper respiratory tract. Increased production of bradykinin secondary to increased plasma kallikrein activity is the primary cause of attacks. Dental procedures cause emotional stress and mechanical trauma and may also initiate attacks. The most feared complication is asphyxiation as a result of laryngeal oedema. Cases that resulted in death after tooth extraction have been reported, so dentists and oral and maxillofacial surgeons should take maximum care in the treatment of patients with HAO, consult with the patient's doctor, and ensure that prophylaxis is given before the procedure. They should work as atraumatically as possible and use procedures to minimise stress. In the event of an attack of HAO, despite all the correct measures having been taken, the procedure should be terminated immediately and treatment of the attack started as soon as possible. The first drugs for the treatment of acute attacks are C1-INH (C1 inhibitor), ecallantide, or icatibant.

Subcutaneous C1 inhibitor for prevention of attacks of hereditary angioedema: additional outcomes and subgroup analysis of a placebo-controlled randomized study

Background

Hereditary angioedema (HAE) is a debilitating disorder resulting from C1-esterase inhibitor (C1-INH) deficiency. In the COMPACT phase 3 study the prophylactic use of a subcutaneous C1 inhibitor (C1-INH [SC], HAEGARDA^®, CSL Behring) twice weekly significantly reduced the frequency of acute edema attacks. Analysis of treatment effects by subgroups, onset of effect, and other exploratory analysis have not been reported.

Methods

This is a post hoc exploratory analysis on data from the randomized, placebo-controlled COMPACT study. 90 patients with C1-INH-HAE were randomized to 1 of 4 treatment sequences: C1-INH (SC) 40 or 60 IU/kg of body weight twice weekly for 16 weeks, preceded or followed by a placebo period. The pre-specified primary efficacy endpoint was the time-normalized number of HAE attacks, and pre-specified secondary efficacy endpoints were the percentage of patients with a certain treatment response (≥ 50% reduction on C1-INH (SC) versus placebo in the time-normalized number of attacks) and the time-normalized number of use of rescue medication. Pre-specified exploratory endpoints included severity of attacks, alone and combined with rescue medication use. Post hoc analyses included exploration of onset of effect and clinical assessment of patients with < 50% of response.

Results

Subgroup findings by various patient characteristics showed a consistent preventive effect of C1-INH (SC). In a post hoc analysis of attacks, the onset of the preventive effect within the first 2 weeks after treatment initiation in COMPACT showed that 10/43 patients (23%) experienced attacks of any severity with 60 IU/kg versus 34/42 patients (81%) with placebo. The need for rescue medication was tenfold lower with 60 IU/kg (35 treated attacks) versus placebo (358 treated attacks). A qualitative analysis of the 4 patients treated with 60 IU/kg and with < 50% reduction of attacks demonstrated a reduction in severity of attacks, rescue medication use, and symptom days which was considered a clinically meaningful treatment effect.

Conclusions

C1-INH (SC) prophylaxis demonstrated a preventive treatment effect with evidence of benefit within 2 weeks. A consistent treatment effect at recommended C1-INH (SC) dosing was evident in all subgroups of patients with type I/II HAE and by various measures of disease and treatment burden.

Trial registration EU Clinical Trials Register, 2013-000916-10, Registered 10 December 2013, https://www.clinicaltrialsregister.eu/ctr-search/trial/2013-000916-10; ClinicalTrials.gov Register, NCT01912456, Registered 31 July 2013, https://clinicaltrials.gov/ct2/show/NCT01912456.

Long-Term Outcomes with Subcutaneous C1-Inhibitor Replacement Therapy for Prevention of Hereditary Angioedema Attacks

BACKGROUND

For the prevention of attacks of hereditary angioedema (HAE), the efficacy and safety of subcutaneous human C1-esterase inhibitor (C1-INH[SC]; HAEGARDA, CSL Behring) was established in the 16-week Clinical Study for Optimal Management of Preventing Angioedema with Low-Volume Subcutaneous C1-Inhibitor Replacement Therapy (COMPACT).

OBJECTIVE

To assess the long-term safety, occurrence of angioedema attacks, and use of rescue medication with C1-INH(SC).

METHODS

Open-label, randomized, parallel-arm extension of COMPACT across 11 countries. Patients with frequent angioedema attacks, either study treatment-naive or who had completed COMPACT, were randomly assigned (1:1) to 40 IU/kg or 60 IU/kg C1-INH(SC) twice per week, with conditional uptitration to optimize prophylaxis (ClinicalTrials.gov registration no. NCT02316353).

RESULTS

A total of 126 patients with a monthly attack rate of 4.3 in 3 months before entry in COMPACT were enrolled and treated for a mean of 1.5 years; 44 patients (34.9%) had more than 2 years of exposure. Mean steady-state C1-INH functional activity increased to 66.6% with 60 IU/kg. Incidence of adverse events was low and similar in both dose groups (11.3 and 8.5 events per patient-year for 40 IU/kg and 60 IU/kg, respectively). For 40 IU/kg and 60 IU/kg, median annualized attack rates were 1.3 and 1.0, respectively, and median rescue medication use was 0.2 and 0.0 times per year, respectively. Of 23 patients receiving 60 IU/kg for more than 2 years, 19 (83%) were attack-free during months 25 to 30 of treatment.

CONCLUSIONS

In patients with frequent HAE attacks, long-term replacement therapy with C1-INH(SC) is safe and exhibits a substantial and sustained prophylactic effect, with the vast majority of patients becoming free from debilitating disease symptoms.

Quantification of human complement C2 protein using an automated turbidimetric immunoassay

BACKGROUND

The measurement of complement components is clinically useful where a deficiency is suspected, or where excessive activation and consumption are present in disease. C2 deficiency carries an increased risk of developing systemic lupus erythematosus, recurrent infections and atherosclerosis. In this study, we have evaluated The Binding Site's Human Complement C2 SPAPLUS® assay.

METHODS

Linearity was tested using 13 sample dilutions covering the standard measuring range. Within- and between-assay variabilities were calculated using five samples with different C2 concentrations. The correlation between C2 concentrations in EDTA-plasma and serum was assessed, as was the correlation between C2 measurements by the automated assay and radial immunodiffusion. C2 concentrations were compared with CH50 activity, and quantified in individuals with homozygous or heterozygous C2 deficiency, acquired angioedema and patients with chronic inflammatory conditions.

RESULTS

The assay was linear across the measuring range (3.8-42.3 mg/L). Intra- and interassay variability were 2.3%-3.8% and 0%-3.3%, respectively. Comparison between C2 measurements in EDTA-plasma and serum provided a strong correlation (p<0.0001, R2=0.82, slope 0.92), as did the correlation between the automated and radial immunodiffusion methods (p<0.0001, R2=0.89, slope 1.07). A positive correlation between C2 concentration and CH50 activity was demonstrated (p<0.0001, R2=0.48). Significant differences were observed between the median C2 concentrations obtained in healthy controls and the patient clinical samples, with homozygous C2-deficient patients giving below detectable results.

CONCLUSIONS

This C2 SPAPLUS® assay allows the automated, rapid and precice quantification of complement C2 protein and could therefore be considered as a replacement for older, more time-consuming methods.

Rare Diseases with Periodontal Manifestations

Background: The object of this paper was to provide an overview of rare diseases (RDs) with periodontal manifestations and allocate them to relevant categories. Methods: In ROMSE, a database for “Rare Diseases with Orofacial Involvement”, all 541 entities were analyzed with respect to manifestations of periodontal relevance. Inclusion criteria were periodontally relevant changes to the oral cavity, in accordance with the 2018 version of the Classification of Periodontal and Peri-Implant Diseases and Conditions. Rare diseases were recorded, using the methodology described, and subsequently compared with the Orphanet Classification of Rare Diseases. Results: A total of 76 RDs with periodontal involvement were recorded and allocated in accordance with the Classification of Periodontal and Peri-Implant Diseases and Conditions. Of the 541 RDs analyzed as having known orofacial manifestations, almost 14 percent indicated a periodontally compromised dentition. Conclusions: Around 14 percent of RDs with an orofacial involvement showed periodontally relevant manifestations, which present not only as a result of gingivitis and periodontitis, but also gingival hyperplasia in connection with an underlying disease. Thus, dentists play an important role in therapy and early diagnoses of underlying diseases based on periodontally relevant manifestations.

C1-esterase inhibitor enhances thrombin generation and spatial fibrin clot propagation in the presence of thrombomodulin

Package inserts for C1-esterase inhibitor (C1INH) products include warnings for an elevated risk of possible thrombosis in certain individuals, referring to thromboembolic events (TEEs) that were reported to occur after C1INH infusions. However, the mechanism(s) that could explain possible development of TEEs due to C1INH remains unknown. In this work, we evaluated plausible impact of C1INH on the protein C (PC) anticoagulant system. We performed thrombin generation (TG) assays (TGA) and analyzed spatial fibrin clot propagation using thrombodynamics in plasma of individual donors after the addition of thrombomodulin (TM) and C1INH. The addition of C1INH was consistent with the plasma concentrations resulting from doses currently approved for the HAE treatment up to ones consistent with off-label use in patients with risk of inflammation. 16 IU/ml of C1INH significantly enhanced thrombin peak (TP) generation in the presence of 12 and 15 nM TM. TG enhancement was observed by the addition of C1INH to make concentrations equal to 2 and 4 IU/ml in some donor plasmas. C1INH addition in the presence of TM enhanced the stop time of spatial clot growth in Thrombodynamics assay. A chromogenic activity assay demonstrated that C1INH inhibited PC activation by thrombin in the presence of TM. Substitution of TM with APC in TGA attenuated the TP enhancing effect of C1INH. The collective results of the present study suggest a concentration dependent C1INH interaction with the PC system. This study introduces a plausible TM-dependent mechanism, that may explain reported TEEs via suppressed production of APC in the presence of C1INH.

Lanadelumab for the Prophylactic Treatment of Hereditary Angioedema with C1 Inhibitor Deficiency: A Review of Preclinical and Phase I Studies

Hereditary angioedema (HAE) with C1 esterase inhibitor (C1-INH) deficiency (C1-INH-HAE) is a rare disease characterized by diminished levels or dysfunctional activity of C1-INH, leading to dysregulated plasma kallikrein activity within the kallikrein-kinin pathway. Symptoms manifest as painful, potentially life-threatening swelling of subcutaneous tissues throughout the body and/or submucosal edema in the upper airway or gastrointestinal tract. Attacks recur with unpredictable frequency, intensity, and duration, placing a heavy burden on patients' daily lives. Despite improved availability of medications for on-demand treatment during attacks and prophylaxis of future attacks, unmet needs remain. Lanadelumab, a fully human monoclonal antibody, may help address some of the limitations of existing prophylactic options (e.g., the need for intravenous administration or frequent dosing). Preclinical studies demonstrate that it is highly potent and specifically inhibits plasma kallikrein, and findings from phase Ia and Ib studies suggest this agent is well tolerated and provides sustained inhibition of plasma kallikrein, allowing for less frequent dosing. The phase III HELP Study (NCT02586805) evaluating the efficacy and safety of lanadelumab in preventing HAE attacks has been completed, and its open-label extension (NCT02741596) is ongoing. Lanadelumab is now approved in the USA and Canada for prophylaxis to prevent attacks of HAE in patients aged ≥ 12 years. This review provides an overview of the discovery and clinical development of lanadelumab, from preclinical through phase Ib studies, characterizing its safety/tolerability, efficacy, and pharmacokinetic and pharmacodynamic profiles. It also highlights how this agent may positively impact clinical care of patients with C1-INH-HAE.

Clinical Features of Hereditary Angioedema in Korean Patients: A Nationwide Multicenter Study

BACKGROUND

Hereditary angioedema (HAE) is a genetically heterogeneous autosomal dominant disorder characterized by recurrent episodes of nonpruritic, nonpitting edema increasing after puberty. It can be fatal due to laryngeal or gastrointestinal (GI) involvement with varied and changing frequency of mortality according to studies published from the Western countries. Epidemiological and clinical data of HAE in Asian countries are sparse. We sought to examine the clinical characteristics of HAE patients in Korea.

METHODS

Patients diagnosed with HAE at 15 tertiary hospitals across the country until 2016 were retrospectively reviewed.

RESULTS

A total of 65 patients diagnosed with HAE by 2016 were identified. The prevalence of HAE was estimated at 1.3/1,000,000 in Korea. Of the 65 patients, 21 (32.3%) were males. A total of 90.8% patients had type I HAE, while the remaining 9.2% patients had type II HAE. The first symptom developed after 20 years in 73.8% of patients, with a mean age 28.4 ± 14.1 years. The age at diagnosis was 36.5 ± 15.8 years, with a mean time delay of 7.8 ± 10.5 years. While the face (82.3%) and extremities (upper 71.0%, lower 62.9%) were the most frequently involved, the GI tract was affected in 40.5% of Korean HAE patients. Prophylaxis was maintained in 62.5% of patients. There was no reported case of death from HAE so far.

CONCLUSIONS

The clinical manifestation and severity of HAE may vary according to ethnicity. HAE is more infrequent and GI involvement is less likely in Korea compared with Western countries.

A missense mutation in the plasminogen gene, within the plasminogen kringle 3 domain, in hereditary angioedema with normal C1 inhibitor

Hereditary angioedema (HAE) is a genetically heterogeneous disease that is characterized by recurrent skin swelling, abdominal pain attacks, and potentially life-threatening upper airway obstruction. The two classic types, HAE types I and II, are both caused by mutations in the complement C1 inhibitor (SERPING1) gene resulting either in a quantitative or a qualitative deficiency of C1 inhibitor. In so-called HAE type III, in contrast, patients show normal C1 inhibitor measurements in plasma ('HAE with normal C1 inhibitor'). As previously shown by us, one subgroup of 'HAE with normal C1 inhibitor' is caused by mutations of the coagulation factor XII (F12) gene. For the present study, following the exclusion of numerous candidate genes, we screened eight unrelated index patients representing eight 'HAE families with normal C1 inhibitor and no F12 mutation' for mutations in the plasminogen (PLG) gene. A rare non-conservative missense mutation was newly identified in exon 9 of the PLG gene. This mutation (c.1100A > G), encountered in three out of eight patients, predicts a lysine-to-glutamic acid substitution in position 311 of the mature protein (p.Lys311Glu). Using isoelectric focusing of plasma samples followed by an immunoblotting procedure we demonstrated that the presence of the mutation is associated with a dysplasminogenemia, namely the presence of an aberrant plasminogen protein. The predicted structural and functional impact of the mutation, its absence in 139 control individuals, and its co-segregation with the phenotype in three large families provide strong support that it causes disease. Extending a previously proposed gene-based alphabetic nomenclature for the various HAE types one may use the term 'HAE type C' for the HAE entity described here.

Perfluorohexadecanoic acid increases paracellular permeability in endothelial cells through the activation of plasma kallikrein-kinin system

Per- and polyfluoroalkyl substances (PFASs) are ubiquitous and high persistent in human blood, thus potentially inducing a myriad of deleterious consequences. Plasma kallikrein-kinin system (KKS), which physiologically regulates vascular permeability, is vulnerable to exogenous stimulators, like PFASs with long-chain alkyl backbone substituted by electronegative fluorine. The study on the interactions of PFASs with the KKS and the subsequent effects on vascular permeability would be helpful to illustrate how the chemicals penetrate the biological vascular barriers to reach different tissues. In present study, three representative PFASs, including perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexadecanoic acid (PFHxDA), were investigated for their effects on the activation of the KKS, paracellular permeability in human retina endothelial cells (HRECs) and integrity of the adherens junctions. In contrast to either PFOS or PFOA, PFHxDA efficiently triggered KKS activation in a concentration-dependent manner based on protease activity assays. The plasma activated by PFHxDA significantly increased paracellular permeability of HRECs through the degradation of adherens junctions. As evidenced by the antagonistic effect of aprotinin, PFHxDA-involved effects on vascular permeability were mediated by KKS activation. The results herein firstly revealed the mechanistic pathway for PFHxDA induced effects on vascular endothelial cells. Regarding the possible structure-related activities of the chemicals, this finding would be of great help in the risk assessment of PFASs.

Diminished capacity of opsonization and immune complex solubilization, and detection of anti-C1q antibodies in sera from patients with hereditary angioedema

BACKGROUND

Hereditary angioedema (HAE) is an autosomal dominant disease caused by deficiency of C1 esterase inhibitor. Symptoms of HAE include edema, which can potentially cause suffocation. Some patients with HAE exhibit immunological abnormalities, which could prevent an accurate diagnosis. Low levels of complement components are characteristic of HAE and in other settings are thought to reduce elimination of apoptotic cells and immune complex (IC). Thus, we aimed to experimentally clarify the mechanism of immunological abnormalities using sera from HAE patients.

METHODS

Serum samples from 18 patients with HAE were collected when free from angioedema attack and compared with normal human pooled sera (NHPS) from 20 healthy volunteers. Opsonization was measured as the rate of phagocytosis of apoptotic Jurkat cells by macrophages differentiated from THP-1 cells incubated with serum. IC solubilization in serum was analyzed by quantifying peroxidase released from a synthetic IC composed of peroxidase and anti-peroxidase antibodies. Anti-C1q antibody levels were detected using an enzyme-linked immunosorbent assay.

RESULTS

Serological immunological abnormalities were detected in 12 patients. Opsonization in serum samples from each patient with HAE was lower than that in NHPS (∼20% versus 70%, respectively). The rate of IC solubilization was lower in serum from HAE patients than NHPS. Some patients had high serum anti-C1q antibody levels with increased serum IC levels.

CONCLUSIONS

Sera from patients with HAE exhibit anti-C1q antibodies, with a lower capacity for opsonization and IC solubilization. This may be associated with immunological abnormalities and should be investigated further to facilitate accurate diagnosis of HAE.

The complement and contact activation systems: partnership in pathogenesis beyond angioedema

The blood plasma contains four biologically important proteolytic cascades, which probably evolved from the same ancestral gene. This in part may explain why each cascade has very similar "initiating trigger" followed by sequential and cascade-like downstream enzymatic activation pattern. The four cascades are: the complement system, the blood clotting cascade, the fibrinolytic system, and the kallikrein-kinin system. Although much has been written about the interplay between all these enzymatic cascades, the cross-talk between the complement and the kinin generating systems has become particularly relevant as this interaction results in the generation of nascent molecules that have significant impact in various inflammatory diseases including angioedema and cancer. In this review, we will focus on the consequences of the interplay between the two systems by highlighting the role of a novel molecular link called gC1qR. Although this protein was first identified as a receptor for C1q, it is now recognized as a multiligand binding cellular protein, which serves not only as C1q receptor, but also as high affinity (K_D  ≤ 0.8 nM) binding site for both high molecular weight kininogen (HK) and factor XII (FXII). At inflammatory sites, where atherogenic factors such as immune complexes and/or pathogens can activate the endothelial cell into a procoagulant and proinflammatory surface, the two pathways are activated to generate vasoactive peptides that contribute in various ways to the inflammatory processes associated with numerous diseases. More importantly, since recent observations strongly suggest an important role for both pathways in cancer, we will focus on how a growing tumor cluster can employ the byproducts derived from the two activation systems to ensure not only its survival and growth, but also its escape into distal sites of colonization.

Complement in clinical medicine: Clinical trials, case reports and therapy monitoring

Research during past decades made it evident that complement is involved in more tasks than fighting infections, but has important roles in other immune surveillance and housekeeping functions. If the balance between complement activation and regulation is out of tune, however, complement can quickly turn against the host and contribute to adverse processes that result in various clinical conditions. Whereas clinical awareness was initially focused on complement deficiencies, excessive activation and insufficient regulation are frequently the dominant factors in complement-related disorders. The individual complement profile of a patient often determines the course and severity of the disease, and the pathophysiological involvement of complement may be highly diverse. As a consequence, complement assays have evolved as essential tools not only in initial diagnosis but also for following disease progression and for monitoring complement-targeted therapies, which become increasingly available in routine clinical use. We herein review the current state of complement-directed drug candidates in clinical evaluation and provide an overview of extended indications considered for the FDA-approved inhibitor eculizumab. Furthermore we review the literature describing cases reports and case series where eculizumab has been used "off-label". Finally, we give a summary of the currently available tests to measure complement profiles and discuss their suitability in diagnostics and treatment monitoring. With complement finally entering the clinical arena, there are intriguing opportunities for treating complement-mediated diseases. However, this progress also requires a new awareness about complement pathophysiology, adequate diagnostic tools and suitable treatment options among clinicians treating patients with such disorders.

[Management of patients with bradykinin-mediated angioedema in oral and maxillofacial surgery]

Bradykinin-mediated angioedema (AE) is a rare disease characterized by recurrent cutaneous or mucosal angioedema. This hereditary or acquired disease is of rapid installation, non-pruritic, usually painless and can affect the face, lips, larynx, gastrointestinal tract or extremities. When the affected area involves the upper respiratory tract, laryngeal angioedema can lead to imminent death by asphyxia. This is the reason for the high mortality rate (30 %) in undiagnosed or improperly managed patients. High-risk situations in oral and maxillofacial surgery procedures should be identified preoperatively. Short-term prophylaxis must be carried-out prior to any procedure that may trigger an attack. A multi-site reference center (CREAK) has been created to help clinicians to manage this disease. This article reviews the pathophysiologic mechanisms, the clinical presentations, the possible treatments, the acute strategies for attacks and different prophylactic possibilities in oral and maxillofacial surgery.

Prevention of Hereditary Angioedema Attacks with a Subcutaneous C1 Inhibitor

BACKGROUND

Hereditary angioedema is a disabling, potentially fatal condition caused by deficiency (type I) or dysfunction (type II) of the C1 inhibitor protein. In a phase 2 trial, the use of CSL830, a nanofiltered C1 inhibitor preparation that is suitable for subcutaneous injection, resulted in functional levels of C1 inhibitor activity that would be expected to provide effective prophylaxis of attacks.

METHODS

We conducted an international, prospective, multicenter, randomized, double-blind, placebo-controlled, dose-ranging, phase 3 trial to evaluate the efficacy and safety of self-administered subcutaneous CSL830 in patients with type I or type II hereditary angioedema who had had four or more attacks in a consecutive 2-month period within 3 months before screening. We randomly assigned the patients to one of four treatment sequences in a crossover design, each involving two 16-week treatment periods: either 40 IU or 60 IU of CSL830 per kilogram of body weight twice weekly followed by placebo, or vice versa. The primary efficacy end point was the number of attacks of angioedema. Secondary efficacy end points were the proportion of patients who had a response (≥50% reduction in the number of attacks with CSL830 as compared with placebo) and the number of times that rescue medication was used.

RESULTS

Of the 90 patients who underwent randomization, 79 completed the trial. Both doses of CSL830, as compared with placebo, reduced the rate of attacks of hereditary angioedema (mean difference with 40 IU, -2.42 attacks per month; 95% confidence interval [CI], -3.38 to -1.46; and mean difference with 60 IU, -3.51 attacks per month; 95% CI, -4.21 to -2.81; P<0.001 for both comparisons). Response rates were 76% (95% CI, 62 to 87) in the 40-IU group and 90% (95% CI, 77 to 96) in the 60-IU group. The need for rescue medication was reduced from 5.55 uses per month in the placebo group to 1.13 uses per month in the 40-IU group and from 3.89 uses in the placebo group to 0.32 uses per month in the 60-IU group. Adverse events (most commonly mild and transient local site reactions) occurred in similar proportions of patients who received CSL830 and those who received placebo.

CONCLUSIONS

In patients with hereditary angioedema, the prophylactic use of a subcutaneous C1 inhibitor twice weekly significantly reduced the frequency of acute attacks. (Funded by CSL Behring; COMPACT EudraCT number, 2013-000916-10 , and ClinicalTrials.gov number, NCT01912456 .).

MR imaging of intestinal angioedema related to angiotensin-converting enzyme inhibitors: Report of three cases and review of literature

Angioedema is a condition in which an increase in vascular permeability leads to the swelling of body tissues. There are both hereditary and acquired forms of the disease, with the latter often associated with the administration of angiotensin-converting enzyme inhibitor medication. Involvement of the intestinal tract is a rare manifestation of angioedema, and can present with abdominal pain, nausea, and vomiting. It is critical for radiologists to be aware of this entity, as they may have the only opportunity to make the diagnosis. We present three cases of intestinal angioedema diagnosed on MRI with discussion of the imaging findings.

Viral-derived complement inhibitors: current status and potential role in immunomodulation

The complement system is one of the body's major innate immune defense mechanisms in vertebrates. Its function is to detect foreign bodies and promote their elimination through opsonisation or lysis. Complement proteins play an important role in the immunopathogenesis of several disorders. However, excessive complement activation does not confer more protection but instead leads to several autoimmune and inflammatory diseases. With inappropriate activation of the complement system, activated complement proteins and glycoproteins may damage both healthy and diseased tissues. Development of complement inhibitors represents an effective approach in controlling dysregulated complement activity and reducing disease severity, yet few studies have investigated the nature and role of novel complement inhibitory proteins of viral origin. Viral complement inhibitors have important implications in understanding the importance of complement inhibition and their role as a promising novel therapeutic approach in diseases caused by dysregulated complement function. In this review, we discuss the role and importance of complement inhibitors derived from several viruses in the scope of human inflammatory and autoimmune diseases.

Hereditary angio-oedema with C1 inhibitor deficiency: Characteristics and diagnostic delay of Czech patients from one centre

BACKGROUND

Hereditary angio-oedema (HAE) is manifested by repeated episodes of localised subcutaneous or sub-mucosal oedema. Symptoms are extremely variable in frequency, localisation, and severity. Atypical or mild clinical symptoms of the disease may lead to erroneous diagnosis, causing diagnostic delay. The goal of this study was to assess how diagnostic delay has changed over 33 years at a single referral centre.

METHODS

We analysed diagnostic delay and first symptoms of HAE in patients who were diagnosed at an immunology department between 1980 and 2013. Patient's records were analysed.

RESULTS

The median diagnostic delay in 77 HAE type 1 and 2 patients was seven (range, 0-42) years. The difference observed in diagnostic delay between probands (18 [0-42] years) and others (1 [0-37] year) was significant (p<0.001). Our data show a significant negative correlation between the length of diagnostic delay and the year of diagnosis in our group of patients (p=0.024). The median age of first symptoms among all HAE patients (N=64) was 17 (1-40) years. The first symptoms of HAE in 64 patients were analysed. Twenty-six patients had abdominal, seventeen peripheral, five facial, two urogenital, and three had laryngeal oedema as the first manifestation of the disease. The last death that was attributed to HAE was in 1977.

CONCLUSIONS

Our observations demonstrate improved awareness of HAE among physicians, as documented by the significant decrease in diagnostic delay. It is believed that earlier treatment will improve patient quality of life and life expectancy.

Paediatric hereditary angioedema: a survey of UK service provision and patient experience

Hereditary angioedema (HAE) is a rare disease characterized by episodes of potentially life-threatening angioedema. For affected children in the United Kingdom, there are relatively few data regarding disease prevalence, service organization and the humanistic burden of the disease. To improve knowledge in these areas, we surveyed major providers of care for children with HAE. A questionnaire was sent to major paediatric centres to determine patient numbers, symptoms, diagnostic difficulties, management and available services. In addition, all patients at a single centre were given a questionnaire to determine the experiences of children and their families. Sixteen of 28 centres responded, caring for a total of 111 UK children. Seven children had experienced life-threatening crises. One-third of patients were on long-term prophylactic medication, including C1 inhibitor prophylaxis in four children. Eight centres reported patients who were initially misdiagnosed. Broad differences in management were noted, particularly regarding indications for long-term prophylaxis and treatment monitoring. We also noted substantial variation in the organization of services between centres, including the number of consultants contributing to patient care, the availability of specialist nurses, the availability of home therapy training and the provision of patient information. Ten of 12 patient/carer questionnaires were returned, identifying three common themes: the need to access specialist knowledge, the importance of home therapy and concerns around the direct effect of angioedema on their life. To our knowledge, this study represents the first dedicated survey of paediatric HAE services in the United Kingdom and provides useful information to inform the optimization of services.

[Diagnosis of hereditary angioedema]

Hereditary angioedema is a rare disease, potentially life-threatening. It requires a specific treatment. Angioedema without wheals associated with abdominal attacks are very specific of this disease. Antigenemy and functional C1Inhibitor assays are necessary for the diagnosis. The hereditary angioedema with normal C1Inh (type III) is a diagnostic challenge. Bradykinin, secondary to kallikrein-kinin system activation is the key mediator of hereditary angioedema. Female are more symptomatic. Attacks can be induced by menstruations, pregnancies or contraceptive pills.

Successful use of daily intravenous infusion of C1 esterase inhibitor concentrate in the treatment of a hereditary angioedema patient with ascites, hypovolemic shock, sepsis, renal and respiratory failure

Hereditary angioedema (HAE) is a rare autosomal dominant disease most commonly associated with defects in C1 esterase inhibitor (C1-INH). HAE manifests as recurrent episodes of edema in various body locations. Atypical symptoms, such as ascites, acute respiratory distress syndrome, and hypovolemic shock, have also been reported. Management of HAE conventionally involves the treatment of acute attacks, as well as short- and long-term prophylaxis. Since attacks can be triggered by several factors, including stress and physical trauma, prophylactic therapy is recommended for patients undergoing surgery. Human plasma-derived C1-INH (pdC1-INH) concentrate is indicated for the treatment of both acute HAE attacks and pre-procedure prevention of HAE episodes in patients undergoing medical, dental, or surgical procedures. We report the first case of a patient with HAE who experienced an abdominal attack precipitated by a retroperitoneal bleed while being converted from warfarin to heparin in preparation for surgery. Subsequently, the patient had a protracted course in hospital with other complications, which included hypovolemic shock, ascites, severe sepsis from nosocomial pneumonia, renal and respiratory failure. Despite intensive interventions, the patient remained in a critical state for months; however, after a trial of daily intravenous infusion of pdC1-INH concentrate (Berinert®, CSL Behring GmbH, Marburg, Germany), clinical status improved, particularly renal function. Therefore, pdC1-INH concentrate may be an effective treatment option to consider for critically-ill patients with HAE.

Hereditary angioedema with F12 mutation: factors modifying the clinical phenotype

BACKGROUND

Hereditary angioedema (HAE) with normal C1 inhibitor (C1Inh) associated with the c.983C>A and c.983C>G mutations of the F12 gene (FXII-HAE) is a rare condition, and presents with highly variable clinical expression. On the basis of data gathered from a large carrier cohort, we assessed the modifiers affecting the clinical phenotype.

METHODS

We analyzed clinical and biological data recorded from 118 mutation carriers (80 symptomatic and 38 asymptomatic), 58 noncarrier relatives from 40 families, and 200 healthy donors. Disease severity was scored in relation to frequency and location of edema, as well as age at disease onset. To predict FXII-HAE disease severity, we analyzed the biological phenotype [C1Inh, C4, spontaneous amidase, angiotensin-I-converting enzyme (ACE), aminopeptidase P (APP), and carboxypeptidase N/M (CPN)] by means of logistic regression (Akaike information criterion) and odds ratio (OR).

RESULTS

Meaningful variables contributed to FXII-HAE, with the kinin catabolism enzymes ACE and CPN exhibiting a significant inverse relationship with disease severity (OR = 0.36, 95% CI 0.23-0.59, P < 0.001; OR = 0.58, 95% CI 0.36-0.91, P < 0.05, respectively). CPN activities were 37.5 (28.5-41.3) nmol/ml/min and 38.5 (32.8-45.6) for FXII-HAE asymptomatic and symptomatic carriers, respectively, and 37.9 (30.5-43.7) nmol/ml/min for noncarriers. Angiotensin-I-converting enzyme activities were 58 (44-76) and 49 (35-59) nmol/ml/min for FXII-HAE asymptomatic and symptomatic carriers, respectively, and 56 (49-66) nmol/ml/min for noncarriers.

CONCLUSIONS

The FXII-HAE is associated with modifiers, for example kinin catabolism enzymes, ACE and CPN, different from those recognized in HAE with C1Inh deficiency.

Management of angioedema without urticaria in the emergency department

Angioedema refers to a localized, transient swelling of the deep skin layers or the upper respiratory or gastrointestinal mucosa. It develops as a result of mainly two different vasoactive peptides, histamine or bradykinin. Pathophysiology, as well as treatment, is different in each case; nevertheless, the resulting signs and symptoms may be similar and difficult to distinguish. Angioedema may occur at any location. When the affected area involves the upper respiratory tract, both forms of angioedema can lead to an imminent upper airway obstruction and a life-threatening emergency. Emergency physicians must have a basic understanding of the pathophysiology underlying this process. Angioedema evaluation in the emergency department (ED) should aim to distinguish between histamine- and bradykinin-induced angioedema, in order to provide appropriate treatment to patients. However, diagnostic methods are not available at the ED setting, neither to confirm one mechanism or the other, nor to identify a cause. For this reason, the management of angioedema should rely on clinical data depending on the particular features of the episode and the patient in each case. The history-taking should be addressed to identify a possible etiology or triggering agent, recording complete information for an ulterior diagnostic study in the outpatient clinic. It is mandatory quickly to recognize and treat a potential life-threatening upper airway obstruction or anaphylaxis. This review focuses on the underlying mechanisms and management of histamine- and bradykinin-induced angioedema at the emergency department and provides an update on the currently available treatments.

C1-esterase inhibitor treatment: preclinical safety aspects on the potential prothrombotic risk

Human plasma-derived C1-esterase inhibitor (C1-INH) is an efficacious and safe treatment for hereditary angioedema. However, thrombotic events in subjects treated with C1-INH at recommended or off-label, high doses have been reported. In this study, we addressed the potential prothrombotic risk of C1-INH treatment in high doses using a non-clinical rabbit model. Following intravenous infusion of C1-INH to rabbits at doses up to 800 IU/kg, the exposure and the pharmacodynamic efficacy of C1-INH in rabbits were confirmed by activity measurements of C1-esterase, and coagulation factors XIa and XIIa, respectively. Potential prothrombotic effects were assessed following induction of venous and arterial thrombosis using in vivo models of venous and arterial stasis, complemented by various in vitro assays of coagulation markers. Administration of C1-INH at doses up to 800 IU/kg did not potentiate thrombus formation during venous stasis. In contrast, inhibition of arterial occlusion was observed upon C1-INH administration when compared with isotonic saline treatment, indicating antithrombotic rather than prothrombotic activity of high dose C1-INH treatment in vivo. This was further confirmed in vitro by decreased thrombin generation, increased activated partial thromboplastin time, clotting time and clot formation time, and inhibition of platelet aggregation. No relevant changes in fibrinolysis or in the levels of thrombin-antithrombin complexes, and prothrombin fragment 1+2 were observed upon high dose C1-INH treatment. The data suggest that treatment of healthy rabbits with high doses of C1-INH could potentially inhibit coagulation and thrombus formation rather than induce a prothrombotic risk.

Pediatric hereditary angioedema

Hereditary angioedema (HAE) is a lifelong illness characterized by recurrent swelling of the skin, intestinal tract, and, ominously, the upper airway. It is caused by inadequate activity of the protein C1-inhibitor, with dysfunction in the kallikrein/bradykinin pathway underlying the clinical symptoms. In addition to the physical symptoms, patients experience significant decrements in vocational and school achievement as well as in overall quality of life. Symptoms often begin in childhood and occur by age 20 in most patients, but life-threatening attacks are uncommon in the pediatric population. The availability of new therapies has transformed the management of HAE.

The protease inhibitor HAI-2, but not HAI-1, regulates matriptase activation and shedding through prostasin

The membrane-anchored serine proteases, matriptase and prostasin, and the membrane-anchored serine protease inhibitors, hepatocyte growth factor activator inhibitor (HAI)-1 and HAI-2, are critical effectors of epithelial development and postnatal epithelial homeostasis. Matriptase and prostasin form a reciprocal zymogen activation complex that results in the formation of active matriptase and prostasin that are targets for inhibition by HAI-1 and HAI-2. Conflicting data, however, have accumulated as to the existence of auxiliary functions for both HAI-1 and HAI-2 in regulating the intracellular trafficking and activation of matriptase. In this study, we, therefore, used genetically engineered mice to determine the effect of ablation of endogenous HAI-1 and endogenous HAI-2 on endogenous matriptase expression, subcellular localization, and activation in polarized intestinal epithelial cells. Whereas ablation of HAI-1 did not affect matriptase in epithelial cells of the small or large intestine, ablation of HAI-2 resulted in the loss of matriptase from both tissues. Gene silencing studies in intestinal Caco-2 cell monolayers revealed that this loss of cell-associated matriptase was mechanistically linked to accelerated activation and shedding of the protease caused by loss of prostasin regulation by HAI-2. Taken together, these data indicate that HAI-1 regulates the activity of activated matriptase, whereas HAI-2 has an essential role in regulating prostasin-dependent matriptase zymogen activation.

Angioedema with normal laboratory values: the next step

When faced with a patient with recurrent swelling, a thorough laboratory evaluation to determine the underlying etiology ensues. When the laboratory work-up is unrevealing, health care practitioners are frequently left in a quandary. This review will attempt to provide up-to-date information on how to approach the diagnosis and management of angioedema in a patient with normal laboratory values. The subtypes that will be reviewed in detail include: hereditary angioedema with normal C1 inhibitor (HAE with normal C1INH), drug-induced angioedema, and idiopathic angioedema. We present literature to aid the physician in the diagnosis and treatment of these disorders.