Hereditary Angioedema Attacks: Local Swelling at Multiple Sites

Hereditary Angioedema: The Clinical Picture of Excessive Contact Activation

Hereditary angioedema is a rare, genetic disorder characterized by painful, debilitating and potentially life-threatening angioedema attacks in subcutaneous and submucosal tissue. While usually unpredictable, attacks can be provoked by a variety of triggers including physical injury and certain medication and are often preceded by prodromal symptoms. Hereditary angioedema has a profound influence on the patients' lives. The fundamental cause of hereditary angioedema in almost all patients is a mutation in the SERPING1 gene leading to a deficiency in C1-inhibitor. Subsequently, the contact activation cascade and kallikrein-kinin pathway are insufficiently inhibited, resulting in excessive bradykinin production triggering vascular leakage. While C1-inhibitor is an important regulator of the intrinsic coagulation pathway, fibrinolytic system and complement cascade, patients do not have an increased risk of coagulopathy, autoimmune conditions or immunodeficiency disorders. Hereditary angioedema is diagnosed based on C1-inhibitor level and function. Genetic analysis is only required in rare cases where hereditary angioedema with normal C1-inhibitor is found. In recent years, new, highly specific therapies have greatly improved disease control and angioedema-related quality of life. This article reviews the clinical picture of hereditary angioedema, the underlying pathophysiology, diagnostic process and currently available as well as investigational therapeutic options.

Isolated Angioedema: A Review of Classification and Update on Management

OBJECTIVE

The purpose of this article is to review the various types of angioedema including diagnosis and treatment.

DATA SOURCES

PubMed search of articles in the English language various types of angioedema STUDY SELECTION: Articles on the subject matter were selected and reviewed.

RESULTS

Herein, a case based approach is presented for discussing the major types of angioedema including: hereditary angioedema (HAE) TypesI/II and normal complement, acquired angioedema, Angiotensin converting enzyme (ACE) induced angioedema, as well as histaminergic and non-histaminergic angioedema. Emerging treatments of HAE including targets of pre-kalikrein, DNA vector technology replacing C1INH protein, and CRIPSR technology targeting PKK among many others are explored. In addition, other causes as well as mimickers of angioedema are briefly reviewed. Finally, a novel algorithm is proposed to help guide the treating physician through the work up and management of patients with suspected idiopathic angioedema unresponsive to conventional therapy with antihistamines.

CONCLUSION

Over the years, many strides have been made in both understanding the pathophysiology of various types of angioedema as well as expansion of treatment options. It is important for clinicians to be aware of current and emerging treatment options. We provide a novel practical algorithm to guide clinicians in challenging cases of idiopathic angioedema refractory to antihistamines.

Assessment and management of disease burden and quality of life in patients with hereditary angioedema: a consensus report

BACKGROUND

Hereditary angioedema (HAE) is a rare disease characterized by unpredictable, potentially life-threatening attacks, resulting in significant physical and emotional burdens for patients and families. To optimize care for patients with HAE, an individualized management plan should be considered in partnership with the physician, requiring comprehensive assessment of the patient's frequency and severity of attacks, disease burden, and therapeutic control. Although several guidelines and consensus papers have been published concerning the diagnosis and treatment of HAE, there has been limited specific clinical guidance on the assessment of disease burden and quality of life (QoL) in this patient population. Practical guidance is critical in supporting effective long-term clinical management of HAE and improving patient outcomes. The objective of this review is to provide evidence-based guidelines for an individualized assessment of disease burden and QoL in patients with HAE.

METHODS

A consensus meeting was held on February 29, 2020, consisting of 9 HAE experts from the United States and Europe with extensive clinical experience in the treatment of HAE. Consensus statements were developed based on a preliminary literature review and discussions from the consensus meeting.

RESULTS

Final statements reflect the consensus of the expert panel and include the assessment of attack severity, evaluation of disease burden, and long-term clinical management of HAE caused by C1-esterase inhibitor deficiency. Patient-reported outcome measures for assessing HAE attack severity and frequency are available and valuable tools; however, attack frequency and severity are insufficient markers of disease severity unless they are evaluated in the broader context of the effect on an individual patient's QoL. QoL assessments should be individualized for each patient and minimally, they should address the interference of HAE with work, school, social, family, and physical activity, along with access to and burden of HAE treatment. Advances in HAE therapies offer the opportunity for comprehensive, individualized treatment plans, allowing patients to achieve minimal attack burden with reduced disease and treatment burden.

CONCLUSION

This consensus report builds on existing guidelines by expanding the assessment of disease burden and QoL measures for patients with HAE.

Evaluation of retinal microvascular perfusion in hereditary angioedema: a case-control study

Evidence supports that hereditary angioedema (HAE) may be considered as a paroxysmal permeability disorder with defective but self-limiting endothelial barrier dysfunction. A potential subclinical abnormal vascular permeability at retinal capillaries could induce damage resulting in retinopathy. We aimed at exploring for the first time the presence of microangiopathy at retinal level from a highly selective cohort of patients with HAE due to C1 esterase inhibitor protein (C1INH) deficiency (type I). We conducted a pilot, prospective, case-control study including 20 type I HAE patients and 20 age−/sex-matched healthy controls (HC). All participants underwent standard ophthalmological examination including visual fields. Superficial and deep capillary plexi in the retina were analyzed by using new optical coherence tomography angiography (OCT-A). A total of 40 eyes from 20 HAE patients and 20 eyes from HC were evaluated. Perimetric indices of visual field were slightly worse in HAE than in controls. OCT-angiograms documented in HAE patients a lower retinal capillary density in both superficial and deep scans and a higher retinal thickness compared to healthy eyes. Our findings firstly documented subclinical abnormalities in retinal microvascular network in type I HAE patients that might be associated with early subtle functional changes. This preliminary evidence supports the hypothesis of a recurrent endothelial barrier failure at retinal level in HAE patients potentially resulting in chronic damage.

Hereditary Angioedema: Insights into inflammation and allergy

Hereditary Angioedema (HAE) is a rare autosomal recessive bradykinin (BK)-mediated disease characterized by local episodes of non-pitting swelling. Initially considered a complement-mediated disease, novel pathogenic mechanisms uncovered in the last decade have revealed new HAE-associated genes and tight physiological relationships among complement, contact, coagulation, fibrinolysis and inflammation. Uncontrolled production of BK due to inefficient regulation of the plasma contact system, increased activity of contact and coagulation factors or a deficient regulation of BK receptor-triggered intracellular signalling are on the basis of HAE pathology. In this new scenario, HAE can result from different mechanisms that may generate distinct clinical phenotypes of the disease. This review focuses in the recent advances and unsolved challenges in our comprehension of this ever increasingly complex pathology.

Hereditary angioedema: Linking complement regulation to the coagulation system

Congenital deficiency of C1 inhibitor, the main inhibitor of the classic complement system pathway, leads to paroxysmal angioedema (hereditary angioedema) that can be debilitating or life-threatening for affected patients. In the past few years many new insights on the pathogenesis of angioedema formation in the presence of low levels of C1 inhibitor has been accumulated. There is a central role for bradykinin that is released upon activation of the kallikrein-kinin system that is insufficiently controlled by adequate levels of C1 inhibitor. As C1 inhibitor also possesses a central regulatory role of other plasma systems, including the contact activation system of coagulation and the plasminogen-plasmin system that governs endogenous fibrinolysis, it is interesting to observe the effects of C1 inhibitor deficiency on activation of these systems and relevance for hemostasis in vivo and thrombo-embolic disease. Interestingly, and despite significant activation of these pathways, C1 inhibitor deficiency is not at all associated with a hemorrhagic tendency or prothrombotic state. New therapeutic options for treatment of C1 inhibitor efficiency have become available in recent years, including various forms of C1 inhibitor concentrate. Restoration of C1 inhibitor levels in patients with hereditary angioedema has not resulted in thrombotic complications or any other relevant disorder associated with the hemostatic system.

Hereditary angioedema: the plasma contact system out of control

The plasma contact system contributes to thrombosis in experimental models. Even though our standard blood coagulation tests are prolonged when plasma lacks contact factors, this enzyme system appears to have a minor (if any) role in hemostasis. In this review, we explore the clinical phenotype of C1 esterase inhibitor (C1-INH) deficiency. C1-INH is the key plasma inhibitor of the contact system enzymes, and its deficiency causes hereditary angioedema (HAE). This inflammatory disorder is characterized by recurrent aggressive attacks of tissue swelling that occur at unpredictable locations throughout the body. Bradykinin, which is considered to be a byproduct of the plasma contact system during in vitro coagulation, is the main disease mediator in HAE. Surprisingly, there is little evidence for thrombotic events in HAE patients, suggesting mechanistic uncoupling from the intrinsic pathway of coagulation. In addition, it is questionable whether a surface is responsible for contact system activation in HAE. In this review, we discuss the clinical phenotype, disease modifiers and diagnostic challenges of HAE. We subsequently describe the underlying biochemical mechanisms and contributing disease mediators. Furthermore, we review three types of HAE that are not caused by C1-INH inhibitor deficiency. Finally, we propose a central enzymatic axis that we hypothesize to be responsible for bradykinin production in health and disease.

The complex alteration in the network of IL-17-type cytokines in patients with hereditary angioedema

Hereditary angioedema (HAE) is a rare autosomic-dominant disorder characterized by a deficiency of C1 esterase inhibitor which causes episodic swellings of subcutaneous tissues, bowel walls and upper airways that are disabling and potentially life-threatening. We evaluated n = 17 patients with confirmed HAE diagnosis during attack and remission state and n = 19 healthy subjects. The samples were tested for a panel of IL (Interleukin)-17-type cytokines (IL-1β, IL-6, IL-10, granulocyte-macrophage colony stimulating factor (GM-CSF), IL-17, IL-21, IL-22, IL-23) and transforming growth factor-beta (TGF-β) subtypes. Data indicate that there are variations of cytokine levels in HAE subjects comparing the condition during the crisis respect to the value in the remission phase, in particular type 17 signature cytokines are increased, whereas IL-23 is unmodified and TGF-β3 is significantly reduced. When comparing healthy and HAE subjects in the remission state, we found a significant difference for IL-17, GM-CSF, IL-21, TGF-β1 and TGF-β2 cytokines. These results confirm and extend our previous findings indicating that in HAE there is operating an inflammatory activation process, which involves also T helper 17 (Th17) cytokines and TGF-β isoforms, associated with localized angioedema attacks and characterized by elevated bradykinin levels.

Coagulation factor XII in thrombosis and inflammation

Combinations of proinflammatory and procoagulant reactions are the unifying principle for a variety of disorders affecting the cardiovascular system. The factor XII-driven contact system starts coagulation and inflammatory mechanisms via the intrinsic pathway of coagulation and the bradykinin-producing kallikrein-kinin system, respectively. The biochemistry of the contact system in vitro is well understood; however, its in vivo functions are just beginning to emerge. Challenging the concept of the coagulation balance, targeting factor XII or its activator polyphosphate, provides protection from thromboembolic diseases without interfering with hemostasis. This suggests that the polyphosphate/factor XII axis contributes to thrombus formation while being dispensable for hemostatic processes. In contrast to deficiency in factor XII providing safe thromboprotection, excessive FXII activity is associated with the life-threatening inflammatory disorder hereditary angioedema. The current review summarizes recent findings of the polyphosphate/factor XII-driven contact system at the intersection of procoagulant and proinflammatory disease states. Elucidating the contact system offers the exciting opportunity to develop strategies for safe interference with both thrombotic and inflammatory disorders.

Intermittent C1-Inhibitor Deficiency Associated with Recessive Inheritance: Functional and Structural Insight

C1-inhibitor is a serine protease inhibitor (serpin) controlling complement and contact system activation. Gene mutations result in reduced C1-inhibitor functional plasma level causing hereditary angioedema, a life-threatening disorder. Despite a stable defect, the clinical expression of hereditary angioedema is unpredictable, and the molecular mechanism underlying this variability remains undisclosed. Here we report functional and structural studies on the Arg378Cys C1-inhibitor mutant found in a patient presenting reduced C1-inhibitor levels, episodically undergoing normalization. Expression studies resulted in a drop in mutant C1-innhibitor secretion compared to wild-type. Notwithstanding, the purified proteins had similar features. Thermal denaturation experiments showed a comparable denaturation profile, but the mutant thermal stability decays when tested in conditions reproducing intracellular crowding.Our findings suggest that once correctly folded, the Arg378Cys C1-inhibitor is secreted as an active, although quite unstable, monomer. However, it could bear a folding defect, occasionally promoting protein oligomerization and interfering with the secretion process, thus accounting for its plasma level variability. This defect is exacerbated by the nature of the mutation since the acquired cysteine leads to the formation of non-functional homodimers through inter-molecular disulphide bonding. All the proposed phenomena could be modulated by specific environmental conditions, rendering this mutant exceptionally vulnerable to mild stress.

Pediatric Hereditary Angioedema as a Cause of Acute Compartment Syndrome of the Hand and Forearm: A Case Report

BACKGROUND

Compartment syndrome of the upper extremity is a surgical emergency that, when left untreated, can have dire consequences. Its causes are numerous, one of which is the uncommon entity hereditary angioedema, an autosomal dominant disease resulting in edema in a variety of potential locations, including the extremities. This is only the second time hereditary angioedema has been mentioned in the literature as a cause of compartment syndrome.

METHODS

We present a case of hereditary angioedema leading to hand and forearm compartment syndrome in a 13-year-old pediatric patient. Diagnosis of hereditary angioedema was made by our Rheumatology colleagues with physical exam and a thorough history, and confirmed by laboratory studies.

RESULTS

Our patient presented with compartment syndrome of the hand and forearm and underwent hand and volar forearm fasciotomies. She was subsequently worked up for hereditary angioedema with laboratory results confirming the diagnosis. She was discharged after a 5-day hospitalization with prophylactic C1-inhibitor therapy.

CONCLUSIONS

Hereditary angioedema is a rare but known cause of compartment syndrome of the upper extremity, and must be considered when patients present with compartment syndrome of unknown etiology. This disease can be diagnosed by laboratory studies and symptoms can be controlled with medical therapy.

Bradykinin: Inflammatory Product of the Coagulation System

Episodic and recurrent local cutaneous or mucosal swelling are key features of angioedema. The vasoactive agents histamine and bradykinin are highly implicated as mediators of these swelling attacks. It is challenging to assess the contribution of bradykinin to the clinical expression of angioedema, as accurate biomarkers for the generation of this vasoactive peptide are still lacking. In this review, we will describe the mechanisms that are responsible for bradykinin production in hereditary angioedema (HAE) and the central role that the coagulation factor XII (FXII) plays in it. Evidently, several plasma parameters of coagulation change during attacks of HAE and may prove valuable biomarkers for disease activity. We propose that these changes are secondary to vascular leakage, rather than a direct consequence of FXII activation. Furthermore, biomarkers for fibrinolytic system activation (i.e. plasminogen activation) also change during attacks of HAE. These changes may reflect triggering of the bradykinin-forming mechanisms by plasmin. Finally, multiple lines of evidence suggest that neutrophil activation and mast-cell activation are functionally linked to bradykinin production. We put forward the paradigm that FXII functions as a ‘sensor molecule’ to detect conditions that require bradykinin release via crosstalk with cell-derived enzymes. Understanding the mechanisms that drive bradykinin generation may help to identify angioedema patients that have bradykinin-mediated disease and could benefit from a targeted treatment.

Hereditary and acquired C1-inhibitor-dependent angioedema: from pathophysiology to treatment

Uncontrolled generation of bradykinin (BK) due to insufficient levels of protease inhibitors controlling contact phase (CP) activation, increased activity of CP proteins, and/or inadequate degradation of BK into inactive peptides increases vascular permeability via BK-receptor 2 (BKR2) and results in subcutaneous and submucosal edema formation. Hereditary and acquired angioedema due to C1-inhibitor deficiency (C1-INH-HAE and -AAE) are diseases characterized by serious and potentially fatal attacks of subcutaneous and submucosal edemas of upper airways, facial structures, abdomen, and extremities, due to inadequate control of BK generation. A decreased activity of C1-inhibitor is the hallmark of C1-INH-HAE (types 1 and 2) due to a mutation in the C1-inhibitor gene, whereas the deficiency in C1-inhibitor in C1-INH-AAE is the result of autoimmune phenomena. In HAE with normal C1-inhibitor, a significant percentage of patients have an increased activity of factor XIIa due to a FXII mutation (FXII-HAE). Treatment of C1-inhibitor-dependent angioedema focuses on restoring control of BK generation by inhibition of CP proteases by correcting the balance between CP inhibitors and BK breakdown or by inhibition of BK-mediated effects at the BKR2 on endothelial cells. This review will address the pathophysiology, clinical picture, diagnosis and available treatment in C1-inhibitor-dependent angioedema focusing on BK-release and its regulation. Key Messages Inadequate control of bradykinin formation results in the formation of characteristic subcutaneous and submucosal edemas of the skin, upper airways, facial structures, abdomen and extremities as seen in hereditary and acquired C1-inhibitor-dependent angioedema. Diagnosis of hereditary and acquired C1-inhibitor-dependent angioedema may be troublesome as illustrated by the fact that there is a significant delay in diagnosis; a certain grade of suspicion is therefore crucial for quick diagnosis. Submucosal edema formation in hereditary and acquired C1-inhibitor-dependent angioedema is potentially life threatening and can occur at any age. To date effective therapies for acute and prophylactic treatment are available.