Metallopeptidase activities in hereditary angioedema: effect of androgen prophylaxis on plasma aminopeptidase P

The effect of estrogen-containing birth control pills on the constituents of bradykinin expression in plasma

Background

Hereditary angioedema with C1-inhibitor deficiency (HAE-C1INH) is a rare autosomal disorder presenting with recurrent angioedema. Estrogen-containing medications trigger angioedema in some patients, and conversely, progesterone may decrease attack frequency. The mechanism by which estrogen may exacerbate angioedema in HAE-C1INH is not well characterized.

Objective

Our aim was to investigate the link between estrogen and bradykinin constituents to better understand the specific underlying triggers that may exacerbate angioedema in patients with HAE-C1INH.

Methods

As estrogen is contraindicated for patients with HAE-C1INH, females without a history of angioedema were recruited to evaluate whether estrogen-containing oral contraceptive pills (OCPs) alter plasma protein levels of bradykinin, cleaved high-molecular-weight kininogen (cHK), and activated factor XII (FXIIa). Blood (plasma) was collected before initiation of OCP administration and 3 months thereafter. High-molecular-weight kininogen (HK) was measured by ELISA and FXIIa and cHK were analyzed by Western blot analysis.

Results

A total of 12 adult females without HAE-CINH (aged <40 years) had a median baseline plasma HK level of 33,976 ng/mL. After 3 months of OCP therapy, their median HK level increased to 38,202 ng/mL. With OCPs, there was also a significant increase in level of FXIIa protein (P <.01), as well as an increase in cHK protein level.

Conclusion

This preliminary study, performed in females without HAE-C1INH, suggests that estrogen may exacerbate angioedema by increasing the production of cHK and FXIIa.

Hereditary angioedema with normal C1 inhibitor associated with carboxypeptidase N deficiency

Background

Hereditary angioedema (HAE) is a potentially life-threatening disorder characterized by recurrent episodes of subcutaneous or submucosal swelling. HAE with normal C1 inhibitor (HAE-nC1-INH) is an underdiagnosed condition. Although the association with genetic variants has been identified for some families, the genetic causes in many patients with HAE-nC1-INH remain unknown. The role of genes associated with bradykinin catabolism is not fully understood.

Objective

We sought to investigate the biological parameters and the genes related to kallikrein-kinin system in families with a clinical phenotype of HAE-nC1-INH and presenting with a carboxypeptidase N (CPN) deficiency.

Methods

This study includes 4 families presenting with HAE-nC1-INH and CPN deficiency. Patients' clinical records were examined, biological parameters of kallikrein-kinin system were measured, and genetics was analyzed by next-generation sequencing and Sanger sequencing. Predictive algorithms (Human Splicing Finder, Sorting Intolerant From Tolerant, Polymorphism Phenotyping v2, MutationTaster, and ClinPred) were used to classify variants as affecting splicing, as benign to deleterious, or as disease-causing.

Results

Patients presented with angioedema and urticaria, mainly on face/lips, but also with abdominal pain or laryngeal symptoms. Affected patients displayed low CPN activity-30% to 50% of median value in plasma. We identified 3 variants of the CPN1 gene encoding the catalytic 55-kDa subunit of CPN: c.533G>A, c.582A>G, and c.734C>T. CPN deficiency associated with genetic variants segregated with HAE-nC1-INH symptoms in affected family members.

Conclusions

CPN1 gene variants are associated with CPN deficiency and HAE-nC1-INH symptoms in 4 unrelated families. Genetic CPN deficiency may contribute to bradykinin and anaphylatoxin accumulation, with synergistic effects in angioedema and urticarial symptoms.

Myeloid lineage cells evince distinct steady-state level of certain gene groups in dependence on hereditary angioedema severity

Hereditary angioedema (HAE) is a rare genetic disorder with variable expressivity even in carriers of the same underlying genetic defect, suggesting other genetic and epigenetic factors participate in modifying HAE severity. Recent knowledge indicates the role of immune cells in several aspects of HAE pathogenesis, which makes monocytes and macrophages candidates to mediate these effects. Here we combined a search for HAE phenotype modifying gene variants with the characterization of selected genes' mRNA levels in monocyte and macrophages in a symptom-free period. While no such gene variant was found to be associated with a more severe or milder disease, patients revealed a higher number of dysregulated genes and their expression profile was significantly altered, which was typically manifested by changes in individual gene expression or by strengthened or weakened relations in mutually co-expressed gene groups, depending on HAE severity. SERPING1 showed decreased expression in HAE-C1INH patients, but this effect was significant only in patients carrying mutations supposedly activating nonsense-mediated decay. Pro-inflammatory CXC chemokine superfamily members CXCL8, 10 and 11 were downregulated, while other genes such as FCGR1A, or long non-coding RNA NEAT1 were upregulated in patients. Co-expression within some gene groups (such as an NF-kappaB function related group) was strengthened in patients with a severe and/or mild course compared to controls. All these findings show that transcript levels in myeloid cells achieve different activation or depression levels in HAE-C1INH patients than in healthy controls and/or based on disease severity and could participate in determining the HAE phenotype.

A safety review of prophylaxis drugs for adolescent patients with hereditary angioedema

INTRODUCTION

Hereditary angioedema (HAE) is characterized by recurrent subcutaneously and/or submucosally localized edematous swellings. The first symptoms often appear in childhood, and they may become more frequent and severe in puberty. Since the appearance of HAE attacks is unpredictable regarding the localization and the frequency, the attacks put a significant burden on the patients and crucially impacts their quality of life.

AREAS COVERED

This review article analyzes the safety data acquired from the clinical trials conducted with the currently available medicinal products for the prophylactic treatment of hereditary angioedema due to C1 inhibitor deficiency and the safety data of observatory studies based on clinical practice. A review of the published literature was conducted using the PubMed database, clinical trials from ClinicalTrials.gov, and abstracts published at scientific conferences.

EXPERT OPINION

The currently available therapeutic products have a good safety and efficiency profile and the international guidelines recommend them as first-line treatments. The choice should be made based on the evaluation of the availability and the preference of the patient.

Trends in Treatments With Disease-Specific and Interfering Drugs in Patients With Hereditary Angioedema in Sweden

BACKGROUND

Hereditary angioedema (HAE) is caused by low levels of or defects in C1 inhibitor. Although disease activity may be modified by prophylaxis, emergency treatment, treatment for comorbidities, and oral contraceptives, the extent of their use is unclear.

OBJECTIVE

To investigate trends in the use of disease-specific and interfering drugs in patients with HAE compared with the general population in Sweden.

METHODS

In a nationwide, longitudinal study, 239 patients with HAE and 2 383 controls were compared with the Prescribed Drug Register (2005-2019). These data reflect rates of dispensed prescriptions from pharmacies in Sweden.

RESULTS

Attenuated androgens were used by approximately 10% of patients with HAE. The number of individuals treated with prophylactic plasma-derived C1 inhibitor increased during this period to reach almost 25% in men and 35% in women in 2019. Tranexamic acid was prescribed to 5% to 15% of patients, primarily children and young adults. Rates of prescriptions for icatibant, an emergency medication, showed a steady increase since its introduction in 2010, in particular among middle-aged women, suggesting poorly controlled disease. The use of diuretics, calcium channel blockers, and gestagens was more common in patients with HAE than in controls, whereas angiotensin-converting enzyme inhibitors were rarely collected.

CONCLUSIONS

Despite concerns regarding side effects, approximately 10% of patients with HAE received attenuated androgens for long-term prophylaxis. The common use of emergency medication also suggests poorly controlled disease in many patients, highlighting the need for increased focus on prophylactic treatment.

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.

Interventions for the long-term prevention of hereditary angioedema attacks

BACKGROUND

Hereditary angioedema (HAE) is a serious and potentially life-threatening condition that causes acute attacks of swelling, pain and reduced quality of life. People with Type I HAE (approximately 80% of all HAE cases) have insufficient amounts of C1 esterase inhibitor (C1-INH) protein; people with Type II HAE (approximately 20% of all cases) may have normal C1-INH concentrations, but, due to genetic mutations, these do not function properly. A few people, predominantly females, experience HAE despite having normal C1-INH levels and C1-INH function (rare Type III HAE). Several new drugs have been developed to treat acute attacks and prevent recurrence of attacks. There is currently no systematic review and meta-analysis that included all preventive medications for HAE.

OBJECTIVES

To assess the benefits and harms of interventions for the long-term prevention of HAE attacks in people with Type I, Type II or Type III HAE.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 3 August 2021.

SELECTION CRITERIA

We included randomised controlled trials in children or adults with HAE that used medications to prevent HAE attacks. The comparators could be placebo or active comparator, or both; approved and experimental drug trials were eligible for inclusion. There were no restrictions on dose, frequency or intensity of treatment. The minimum length of four weeks of treatment was required for inclusion; this criterion excluded the acute treatment of HAE attacks.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were 1. HAE attacks (number of attacks per person, per population) and change in number of HAE attacks; 2. mortality and 3. serious adverse events (e.g. hepatic dysfunction, hepatic toxicity and deleterious changes in blood tests). Our secondary outcomes were 4. quality of life; 5. severity of breakthrough attacks; 6. disability and 7. adverse events (e.g. weight gain, mild psychological changes and body hair). We used GRADE to assess certainty of evidence for each outcome.

MAIN RESULTS

We identified 15 studies (912 participants) that met the inclusion criteria. The studies included people with Type I and II HAE. The studies investigated avoralstat, berotralstat, subcutaneous C1-INH, plasma-derived C1-INH, nanofiltered C1-INH, recombinant human C1-INH, danazol, and lanadelumab for the prevention of HAE attacks. We did not find any studies on the use of tranexamic acid for prevention of HAE attacks. All drugs except avoralstat reduced the number of HAE attacks compared with placebo. For breakthrough attacks that occurred despite prophylactic treatment, intravenous and subcutaneous forms of C1-INH and lanadelumab reduced attack severity. It is not known whether other drugs have a similar effect, as the severity of breakthrough attacks in people taking drugs other than C1-INH and lanadelumab was not reported. For quality of life, avoralstat, berotralstat, C1-INH (all forms) and lanadelumab increased quality of life compared with placebo; there were no data for danazol. Four studies reported on changes in disability during treatment with C1-INH, berotralstat and lanadelumab; all three drugs decreased disability compared with placebo. Adverse events, including serious adverse events, did not occur at a rate higher than placebo. However, serious adverse event data and other adverse event data were not available for danazol, which prevented us from drawing conclusions about the absolute or relative safety of this drug. No deaths were reported in the included studies. The analysis was limited by the small number of studies, the small number of participants in each study and the lack of data on older drugs, therefore the certainty of the evidence is low. Given the rarity of HAE, it is not surprising that drugs were rarely directly compared, which does not allow conclusions on the comparative efficacy of the various drugs for people with HAE. Finally, we did not identify any studies that included people with Type III HAE. Therefore, we cannot draw any conclusions about the efficacy or safety of any drug in people with this form of HAE.

AUTHORS' CONCLUSIONS

The available data suggest that berotralstat, C1-INH (subcutaneous, plasma-derived, nanofiltered and recombinant), danazol and lanadelumab are effective in lowering the risk or incidence (or both) of HAE attacks. In addition, C1-INH and lanadelumab decrease the severity of breakthrough attacks (data for other drugs were not available). Avoralstat, berotralstat, C1-INH (all forms) and lanadelumab increase quality of life and do not increase the risk of adverse events, including serious adverse events. It is possible that danazol, subcutaneous C1-INH and recombinant human C1-INH are more effective than berotralstat and lanadelumab in reducing the risk of breakthrough attacks, but the small number of studies and the small size of the studies means that the certainty of the evidence is low. This and the lack of head-to-head trials prevented us from drawing firm conclusions on the relative efficacy of the drugs.

Emerging drugs for the treatment of hereditary angioedema due to C1-inhibitor deficiency

INTRODUCTION

Hereditary angioedema due to C1-inhibitor (C1-INH-HAE) is a rare disease characterized by unpredictable swelling attacks that may be life-threatening when affecting the upper airways. Understanding the pathophysiology of HAE and the mechanism of bradykinin-mediated angioedema allowed the development of new therapies for the treatment of HAE: clinical trials are ongoing to expand the number of drugs available for on-demand treatment and prophylaxis.

AREAS COVERED

Authors discuss the products that have been used to treat this disease for many years and present the most recently marketed products and those which are under development.

EXPERT OPINION

Significant therapeutic progress has been made in HAE. In particular, drugs targeting specific molecules involved in the angioedema formation were developed and studies with new drugs are ongoing. In the coming years, more effective therapies with easier administration route options for on-demand treatment and long-term prophylaxis will be available to treat this disease and the variety of patients. Gene therapy strategies may offer a definitive treatment. High costs of current and new drugs may be a limiting factor for their availability, especially in developing countries.

SERPING1 Variants and C1-INH Biological Function: A Close Relationship With C1-INH-HAE

Hereditary angioedema with C1 Inhibitor deficiency (C1-INH-HAE) is caused by a constellation of variants of the SERPING1 gene (n = 809; 1,494 pedigrees), accounting for 86.8% of HAE families, showing a pronounced mutagenic liability of SERPING1 and pertaining to 5.6% de novo variants. C1-INH is the major control serpin of the kallikrein–kinin system (KKS). In addition, C1-INH controls complement C1 and plasminogen activation, both systems contributing to inflammation. Recognizing the failed control of C1s protease or KKS provides the diagnosis of C1-INH-HAE. SERPING1 variants usually behave in an autosomal-dominant character with an incomplete penetrance and a low prevalence. A great majority of variants (809/893; 90.5%) that were introduced into online database have been considered as pathogenic/likely pathogenic. Haploinsufficiency is a common feature in C1-INH-HAE where a dominant-negative variant product impacts the wild-type allele and renders it inactive. Small (36.2%) and large (8.3%) deletions/duplications are common, with exon 4 as the most affected one. Point substitutions with missense variants (32.2%) are of interest for the serpin structure–function relationship. Canonical splice sites can be affected by variants within introns and exons also (14.3%). For noncanonical sequences, exon skipping has been confirmed by splicing analyses of patients' blood-derived RNAs (n = 25). Exonic variants (n = 6) can affect exon splicing. Rare deep-intron variants (n = 6), putatively acting as pseudo-exon activating mutations, have been characterized as pathogenic. Some variants have been characterized as benign/likely benign/of uncertain significance (n = 74). This category includes some homozygous (n = 10) or compound heterozygous variants (n = 11). They are presenting with minor allele frequency (MAF) below 0.00002 (i.e., lower than C1-INH-HAE frequency), and may be quantitatively unable to cause haploinsufficiency. Rare benign variants could contribute as disease modifiers. Gonadal mosaicism in C1-INH-HAE is rare and must be distinguished from a de novo variant. Situations with paternal or maternal disomy have been recorded (n = 3). Genotypes must be interpreted with biological investigation fitting with C1-INH expression and typing. Any SERPING1 variant reminiscent of the dysfunctional phenotype of serpin with multimerization or latency should be identified as serpinopathy.

Attenuated androgen discontinuation in patients with hereditary angioedema: a commented case series

Background

Hereditary angioedema (HAE) is characterized by potentially severe and life-threatening attacks of localized swelling. Prophylactic therapies are available, including attenuated androgens. Efficacy of attenuated androgens has not been assessed in large, randomized, placebo-controlled trials and can be associated with frequent, and sometimes severe, side effects. As better tolerated targeted therapies become available, attenuated androgen withdrawal is increasingly considered by physicians and their patients with HAE. Attenuated androgens withdrawal has not been systematically studied in HAE, although examination of other disorders indicates that attenuated androgen withdrawal may result in mood disturbances and flu-like symptoms. Standardized protocols for attenuated androgen discontinuation that continue to provide control of attacks while limiting potential attenuated androgen withdrawal symptoms are not established as the outcomes of different withdrawal strategies have not been compared. We aim to describe the challenges of attenuated androgen discontinuation in patients with HAE and how these may continue into the post-androgen period.

Case presentation

We present a retrospective case series of 10 patients with confirmed type I HAE who have discontinued prophylactic treatment with attenuated androgens. The most common reason for attenuated androgen discontinuation was side effects. Attenuated androgens were either immediately withdrawn, tapered and/or overlapped with another treatment. The major challenge of discontinuation was the management of an increased frequency and severity of HAE attacks in some patients.

Conclusions

Healthcare teams need to undertake careful planning and monitoring after attenuated androgens discontinuation, and modify treatment strategies if HAE control is destabilized with an increased number of attacks. Discontinuation of attenuated androgens is definitively an option in an evolving HAE treatment landscape, and outcomes can be favourable with additional patient support and education.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13223-021-00644-0.

Hormonal Effects on Urticaria and Angioedema Conditions

Women appear to be more frequently affected with urticaria and angioedema. Sex hormones are believed to have an important mechanistic role in regulating pathways involved in these conditions. This effect is likely nonspecific for chronic spontaneous urticaria (CSU) or many forms of angioedema (AE), because many other chronic diseases such as asthma are also affected by sex hormones. The role of sex hormones has been better elucidated for hereditary AE, because they have been shown to have multiple effects including upregulation of FXII, an important activator of the kallikrein pathway. However, their role in the underlying pathogenesis for CSU is less clear. Autoimmunity is clearly linked to CSU, which is more common in women. This suggests that sex hormones could act as adjuvants in activating or upregulating autoimmune pathways. The purpose of this review is to discuss in detail the role of sex hormones in CSU and AE and how a better understanding of the impact hormones has on these conditions might lead to new treatment advancements with better clinical outcomes.

Biomarkers in Hereditary Angioedema

A biomarker is a defined characteristic measured as an indicator of normal, biologic, pathogenic processes, or biological responses to an exposure or intervention. Diagnostic biomarkers are used to detect a disease or a subtype of a disease; monitoring biomarkers are measured serially to assess a medical condition; response biomarkers are used to check biologic response following a medical intervention; predictive biomarkers are used to identify patients who are more likely to respond to a medical intervention; and prognostic biomarkers are used to assess the future likelihood of a clinical event. Although biomarkers have been extensively investigated and validated in many diseases and pathologies, very few are currently useful for the diagnosis, evaluation of disease activity, and treatment of hereditary angioedema (HAE). Pathophysiologic pathways involved in HAE reveal a plethora of molecules from the complement, coagulation, and fibrinolysis systems or from the vascular endothelium, which may serve as biomarkers. The most promising candidates, together with their laboratory readout systems, should be evaluated with regard to their analytical and clinical validity and utility. To be highly specific, such biomarkers should be linked to the pathomechanisms of HAE, particularly the bradykinin-generating cascade. Additionally, major advances in high-throughput omics-based technologies may facilitate the discovery of new candidate biomarkers in the future. This review will cover the existing as well as future potential biomarkers that will support the diagnosis, monitor disease activity, and can be used to assess the efficacy of new avenues of therapy of HAE and other forms of angioedema.

Current and Prospective Targets of Pharmacologic Treatment of Hereditary Angioedema Types 1 and 2

Hereditary angioedema (HAE) is a rare disease that causes episodic attacks of subcutaneous and submucosal edema, which can be painful, incapacitating, and potentially fatal. These attacks are mediated by excessive bradykinin production, as a result of uncontrolled activation of the plasma kallikrein/kinin system, which is caused by a C1 esterase inhibitor deficiency or dysfunction in HAE types 1 and 2, respectively. For many years, treatment options were limited to therapies with substantial adverse effects, insufficient efficacy, or difficult routes of administration. Increased insights in the pathophysiology of HAE have paved the way for the development of new therapies with fewer side effects. In the last two decades, several targeted novel therapeutic strategies for HAE have been developed, for both long-term prophylaxis and on demand treatment of acute attacks. This article reviews the advances in the development of more effective and convenient treatment options for HAE and their anticipated effects on morbidity, mortality, and quality of life. The emergence of these improved treatment options will presumably change current HAE guidelines, but adherence to these recommendations may become restricted by high treatment costs. It will therefore be essential to determine the indications and identify the patients that will benefit most from these newest treatment generations. Ultimately, current preclinical research into gene therapies may eventually lead the way towards curative treatment options for HAE. In conclusion, an increasing shift towards the use of highly effective long-term prophylaxis is anticipated, which should drastically abate the burden on patients with hereditary angioedema.

An update on the genetics and pathogenesis of hereditary angioedema

Hereditary angioedema (HAE) is an uncommon genetic disorder characterized by recurrent episodes of edema involving subcutaneous tissue and submucosa. The pathogenesis of HAE reflects an intricate coordinated regulation of components of complement, kinin and hemostatic pathway. Till date, mutations in 4 different genes have been identified to cause HAE which includes serine protease inhibitor G1 (SERPING1), factor XII (F12), plasminogen (PLG) and angiopoietin 1 (ANGPT 1). These mutations lead to increased bradykinin 2 receptor mediated signalling via increased production of bradykinin except mutations in ANGPT1 gene that disturbs the cytoskeletal assembly of vascular endothelial cells. In this review we aim to summarize the recent advances in the pathogenesis and genetics of HAE. We also provide an overview of possible future prospects in the identification of new genetic defects in HAE.

XPNPEP2 is associated with lymph node metastasis in prostate cancer patients

As we reported in our previous studies, TMTP1, a tumor-homing peptide, selectively targets highly metastatic tumors and their metastatic foci. Aminopeptidase P2 (XPNPEP2) is a receptor for TMTP1 tumor-homing peptide. However, the biological and clinical significance of Aminopeptidase P2 in human cancers remains unknown. In this study, the high-density multiple organ tumor tissue array was employed for the analysis of XPNPEP2 expression profiles in human specimens. The results showed that XPNPEP2 was moderately expressed in the normal prostate tissues, but significantly decreased in the prostate cancer. Hence we used TCGA, IHC, and ELISA to further analyze the expression of XPNPEP2 in tissues and serum of prostate cancer patients. In general, XPNPEP2 expression was lower in prostate cancer tissue than in normal prostate tissue, but was higher in prostate cancer tissues with local invasion and LN metastasis than in tissues with localized Pca. Western blot clarified XPNPEP2 had a secreted form in the serum. Then the serums of 128 Pca patients, 70 healthy males and 40 prostate hyperplasia patients were obtained for detecting serum XPNPEP2 levels.The results indicated that the concentration of XPNPEP2 in serums of Pca patients with LN metastasis (142.7 ± 14.40 ng/mL) were significantly higher than levels in Pca patients without LN metastasis (61.63 ± 5.50 ng/mL) (p < 0.01). An ROC analysis revealed that the combination of PSA and XPNPEP2 was more efficient than PSA or XPNPEP2 alone for predicting LN metastasis, especially for Pca patients with low serum PSA levels. In summary, serum XPNPEP2 levels when combined with PSA levels may result in increased sensitivity for predicting LN metastasis in Pca patients, especially for patients with low serum PSA levels.

Identification and Mapping of a 2,009-bp DNA Deletion in SERPING1 of a Hereditary Angioedema Patient

We report a heterozygous, 2,009 base pairs (bps) genomic DNA deletion within the SERPING1 gene that has not previously been reported in a case of type I hereditary angioedema (HAE). The patient is a 28-year-old Han Chinese female living in Hong Kong who has suffered from recurrent angioedema since adolescence, with increasing attack frequency as she entered adulthood; in the past, episodes occurred annually, but now occur every two to three months. The affected areas are not itchy and include common sites such as the left and right forearms, but without throat involvement. The patient also experiences epigastric pain. The patient's mother suffers from similar symptoms. A mutation in the serine protease inhibitor, clade G, member 1 (SERPING1) gene is associated with HAE. Patients with HAE type I commonly carry either a small deletion within SERPING1 or a truncated transcript. We performed a multiplex ligation-dependent probe amplification (MLPA) assay on our indexed patient. Our result suggests a 2,009 bps deletion spanning across exons 5 and 6 within SERPING1. Although earlier literature has described other large DNA deletions encasing exons 5 and 6 in SERPING1, these DNA rearrangements were larger in size between 4 and 6 kbps, and the breakpoint locations were generally not determined due to technical constraints (Pappalardo et al., 2000; Duponchel et al., 2001; Roche et al., 2005; Loules et al., 2018; and Göβwein et al., 2008). Our report describes mapping of this 2,009 bps in SERPING1. Using a combination of molecular techniques, we were able to confirm and locate this large heterozygous genomic DNA deletion that includes both exons 5 and 6 of SERPING1.

Genetic Variation of Kallikrein-Kinin System and Related Genes in Patients With Hereditary Angioedema

Hereditary angioedema (HAE) is an autosomal dominant disease caused by C1-INH deficiency due to mutations in SERPING1 (C1-INH-HAE) in most of the cases, or by specific mutations in factor XII gene, F12 (F12-HAE). Identification of polymorphisms in the genes encoding proteins from key pathways driving HAE can help to understand how genetic diversity contributes to its phenotypic variability. Here, 15 genes related to the Kallikrein-Kinin System (KKS) were analyzed by next generation sequencing in 59 patients with C1-INH-HAE or F12-HAE from Brazil, Denmark and Spain, and 19 healthy relatives in a total of 31 families. We identified 211 variants, from which 23 occurred only in Danish subjects and 79 were found only in Brazilian individuals, resulting in 109/211 variations in common between European and Brazilian population in the HAE families analyzed. BDKRB2 and CPM presented a large number of variants in untranslated regions, 46/49 and 19/24, respectively; whereas ACE (n = 26), SERPING1 (n = 26), CPM (n = 24), and NOS3 (n = 16) genes presented the higher number of variants directly affecting amino acid sequence. Despite the large amount of variants identified, the lack of association between genotype and phenotype indicates that the modulation of HAE symptom requires a more complex regulation, probably involving pathways beyond the KKS, epigenetics and environmental factors. Considering the new HAE types recently described, molecules involved in the regulation of vasculature and in plasminogen activation become promising targets for future genetic studies.

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.

The diagnosis of hereditary angioedema with C1 inhibitor deficiency: a survey of Canadian physicians and laboratories

Background

Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is an autosomal dominant disease resulting in random and unpredictable attacks of swelling. The swelling in C1-INH-HAE is a result of impaired regulation of bradykinin production. The fact that the array of tests needed to diagnose HAE is not always available to the treating physicians is challenging for them and their patients.

Methods

The data for this article were extracted from two distinct surveys. The first survey was conducted among HAE treating physicians and aimed to determine the availability and utilization of the various assays performed to help the diagnosis of C1-INH-HAE. The second survey was conducted with the various laboratories across Canada that performs the assays used in the diagnosis of HAE. The aim of this survey was to determine the availability and profile of the various assays used in the diagnosis of C1-INH-HAE in Canada, thereby ultimately bringing a rational basis for the biological testing.

Results

C1-INH functional assay was widely available in Canada (93%), but was only offered by a small numbers of hospitals meaning that there could be longer delays in the analysis of these samples that may explain why the physicians expressed a lower level of confidence in this assay (59%). Antigenic C1-INH was available to the vast majority of the physicians treating C1-INH-HAE (93%) and was considered reliable by 96% of the respondents. Antigenic C4 was found available to all Canadian physicians and, although with limited specificity, was considered very reliable by all the participants. This study revealed that 81% of physicians were able to order the antigenic C1q and the confidence in this assay was moderate (70%). Concerning genetic testing, the survey revealed that most of the CHAEN members never had to or couldn't order this test.

Conclusion

This study highlights the need for improved education and knowledge exchange, about biological assays available to Canadian physicians and their performance in proper diagnosis of C1-INH-HAE to improve confidence and access to relevant tests.

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.

Icatibant for the treatment of hereditary angioedema with C1-inhibitor deficiency in adolescents and in children aged over 2 years

INTRODUCTION

Hereditary angioedema (HAE) due to C1-inhibitor deficiency (C1-INH-HAE) is a rare disorder with life-threatening complications if untreated. It begins during childhood, and reduces the patient's quality of life. Therefore, the availability of an easily administered agent to relieve unpredictable HAE episodes is indispensable for this age group. Areas covered: Randomized, double-blind, placebo-controlled, open-label extensions and prospective observational studies have proven the safety and efficacy of the subcutaneously administered bradykinin B2 receptor antagonist, icatibant, in the acute treatment of HAE episodes in adult C1-INH-HAE patients. Recently, a Phase 3, multicenter, open-label, non-randomized, single-arm study demonstrated the efficacy, safety, and tolerability of icatibant as an acute treatment for pediatric patients aged 2 years to less than 18 years. Expert commentary: The clinical study in pediatric patients showed that icatibant undergoes rapid absorption, reaches a therapeutic level, and promptly relieves the symptoms. It is well tolerated, and the subcutaneous preparation, presented in a pre-filled syringe, ensures ease of use. It can be administered anytime, anywhere, and instantly - even by the patients themselves, or - in the case of children and adolescents - by a caregiver. Icatibant may greatly contribute to the improvement of the quality of life of pediatric patients.

Investigational drugs in phase I and phase II clinical trials for hereditary angioedema

INTRODUCTION

Hereditary angioedema (HAE) with C1-inhibitor deficiency (C1-INH-HAE) is a rare bradykinin-mediated disease characterized by recurrent subcutaneous and/or submucosal angioedematous attacks (HAE attacks), which occur unpredictably. The recurrent HAE attacks do not respond to conventional treatments, and may evolve into a life-threatening condition; therefore, special therapy is required.

AREAS COVERED

The agents used so far for the acute management of HAE attacks act by blocking the release of bradykinin, or its binding to its receptor. By contrast, the investigational medicinal products under evaluation in Phase I and II clinical trials are targeted at the prevention of HAE attacks. Chemically, these new drugs are small synthetic molecules, oligonucleotides, or antibodies, which inhibit either kallikrein, or Factor XII.

EXPERT OPINION

The key considerations for the development of new medicinal products include more straightforward dosing, self-administration, longer duration of action, and keeping the patient attack-free. This review summarizes the status and the findings of the currently ongoing Phase I and Phase II clinical trials of C1-INH-HAE.

Factor XII-Driven Inflammatory Reactions with Implications for Anaphylaxis

Anaphylaxis is a life-threatening allergic reaction. It is triggered by the release of pro-inflammatory cytokines and mediators from mast cells and basophils in response to immunologic or non-immunologic mechanisms. Mediators that are released upon mast cell activation include the highly sulfated polysaccharide and inorganic polymer heparin and polyphosphate (polyP), respectively. Heparin and polyP supply a negative surface for factor XII (FXII) activation, a serine protease that drives contact system-mediated coagulation and inflammation. Activation of the FXII substrate plasma kallikrein leads to further activation of zymogen FXII and triggers the pro-inflammatory kallikrein-kinin system that results in the release of the mediator bradykinin (BK). The severity of anaphylaxis is correlated with the intensity of contact system activation, the magnitude of mast cell activation, and BK formation. The main inhibitor of the complement system, C1 esterase inhibitor, potently interferes with FXII activity, indicating a meaningful cross-link between complement and kallikrein-kinin systems. Deficiency in a functional C1 esterase inhibitor leads to a severe swelling disorder called hereditary angioedema (HAE). The significance of FXII in these disorders highlights the importance of studying how these processes are integrated and can be therapeutically targeted. In this review, we focus on how FXII integrates with inflammation and the complement system to cause anaphylaxis and HAE as well as highlight current diagnosis and treatments of BK-related diseases.

HAE Pathophysiology and Underlying Mechanisms

Remarkable progress in understanding the pathophysiology and underlying mechanisms of hereditary angioedema has led to the development of effective treatment for this disorder. Progress in three separate areas has catalyzed our understanding of hereditary angioedema. The first is the recognition that HAE type I and type II result from a deficiency in the plasma level of functional C1 inhibitor. This observation has led to a detailed understanding of the SERPING1 mutations responsible for this deficiency as well as the molecular regulation of C1 inhibitor expression and function. The second is that the fundamental cause of swelling is enhanced contact system activation leading to increased generation of bradykinin. Substantial progress has been made in defining the parameters regulating bradykinin generation and catabolism as well as the receptors that transduce the biologic effects of kinins. The third is the understanding that tissue swelling in hereditary angioedema primarily involves the function of endothelial cell adherens junctions. This knowledge is driving increased attention to the role of endothelial biology in determining disease activity in hereditary angioedema. While there has been considerable progress made, large gaps still remain in our knowledge. Important areas that remain poorly understood include the factors that lead to very low plasma functional C1 inhibitor levels, the triggers of contact system activation in hereditary angioedema, and the role of the bradykinin B1 receptor. The phenotypic variability of hereditary angioedema has been extensively documented but never understood. The mechanisms discussed in this chapter likely contribute to this variability. Future progress in understanding these mechanisms should provide new means to improve the diagnosis and treatment of hereditary angioedema.

"Nuts and Bolts" of Laboratory Evaluation of Angioedema

Angioedema, as a distinct disease entity, often becomes a clinical challenge for physicians, because it may cause a life-threatening condition, whereas prompt and accurate laboratory diagnostics may not be available. Although the bedside diagnosis needs to be established based on clinical symptoms and signs, family history, and the therapeutic response, later, laboratory tests are available. Currently, only for five out of the nine different types of angioedema can be diagnosed by laboratory testing, and these occur only in a minority of the patient population. Hereditary angioedema with C1-inhibitor (C1-INH) deficiency type I can be diagnosed by the low C1-INH function and concentration, whereas in type II, C1-INH function is low, but its concentration is normal or even elevated. C1q concentration is normal in both forms. Acquired angioedema with C1-INH deficiency type I is characterized by the low C1-INH function and concentration; however, C1q concentration is also low, and autoantibodies against C1-INH cannot be detected. Complement profile of acquired angioedema with C1-INH deficiency type II is similar to that of type I, but in this form, autoantibodies against C1-INH are present. Hereditary angioedema due to a mutation of the coagulation factor XII can be diagnosed exclusively by mutation analysis of FXII gene. Diagnostic metrics are not available for idiopathic histaminergic acquired angioedema, idiopathic non-histaminergic acquired angioedema, acquired angioedema related to angiotensin-converting enzyme inhibitor, and hereditary angioedema of unknown origin; these angioedemas can be diagnosed by medical and family history, clinical symptoms, and therapeutic response and by excluding the forms previously described. Several potential biomarkers of angioedema are used to date only in research. In the future, they could be utilized into the clinical practice to improve the differential diagnosis, therapy, as well as the prognosis of angioedema.

Hereditary Angioedema as a Metabolic Liver Disorder: Novel Therapeutic Options and Prospects for Cure

Hereditary angioedema (HAE) is a rare autosomal dominant disorder caused by mutations of the SERPING1 or the Factor 12 genes. It is potentially fatal, particularly if not identified at an early stage. Apart from androgens, which are contraindicated in children and in pregnant women, a range of effective, albeit very expensive treatments have recently become available for HAE patients. The cost of these new treatments is beyond the reach of most developing countries. At this time, there is no cure for the disorder. In spite of mutations of the SERPING1 gene, autoimmunity and infections are not prominent features of the condition. Here, we present the argument that HAE should be viewed primarily as a metabolic liver disorder. This conceptual paradigm shift will stimulate basic research and may facilitate new therapeutic approaches to HAE outlined in this paper. We suggest several novel potential treatment options for HAE from the perspectives of clinical immunology, molecular biology, and liver transplantation. Many of these offer the prospect of curing the disorder. The effectiveness of these options is rapidly improving in many cases, and their risks are decreasing. Given the very high costs of treating HAE, some of these curative options may become feasible in the next decade.

Kininogen Cleavage Assay: Diagnostic Assistance for Kinin-Mediated Angioedema Conditions

Background

Angioedema without wheals (AE) is a symptom characterised by localised episodes of oedema presumably caused by kinin release from kininogen cleavage. It can result from a hereditary deficiency in C1 Inhibitor (C1Inh), but it can present with normal level of C1Inh. These forms are typically difficult to diagnose although enhanced kinin production is suspected or demonstrated in some cases.

Objectives

We wanted to investigate bradykinin overproduction in all AE condition with normal C1Inh, excluding cases with enhanced kinin catabolism, and to propose this parameter as a disease biomarker.

Methods

We retrospectively investigated high molecular weight kininogen (HK) cleavage pattern, using gel electrophoresis and immunorevelation. Plasma samples were drawn using the same standardised procedure from blood donors or AE patients with normal C1Inh conditions, normal kinin catabolism, and without prophylaxis.

Results

Circulating native HK plasma concentrations were similar in the healthy men (interquartile range: 98–175μg/mL, n = 51) and in healthy women (90–176μg/mL, n = 74), while HK cleavage was lower (p<0.001) in men (0–5%) than women (3–9%). Patients exhibited lower native HK concentration (p<10⁻⁴; 21–117μg/mL, n = 31 for men; 0–84μg/mL, n = 41 for women) and higher HK cleavage (p<10⁻⁴; 10–30% and 14–89%, respectively) than healthy donors. Pathological thresholds were set at: <72μg/mL native HK, >14.4% HK cleavage for men; <38μg/mL; native HK, >33.0% HK cleavage for women, with >98% specificity achieved for all parameters. In plasma from patients undergoing recovery two months after oestrogen/progestin combination withdrawal (n = 13) or two weeks after AE attack (n = 2), HK cleavage was not fully restored, suggesting its use as a post-attack assay.

Conclusion

As a diagnostic tool, HK cleavage can offer physicians supportive arguments for kinin production in suspected AE cases and improve patient follow-up in clinical trials or prophylactic management.

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.

Homozygosity for a factor XII mutation in one female and one male patient with hereditary angio-oedema

Hereditary angio-oedema (HAE) with normal C1 inhibitor is associated with heterozygous mutations in the factor XII gene (FXII-HAE). We report two Brazilian FXII-HAE families segregating the mutation c.983 C>A (p.Thr328Lys). In each family, one patient with a homozygous mutation was found. The homozygous female patient in family 1 displayed a severe phenotype. However, this falls within the clinical phenotype spectrum reported for heterozygous female mutation carriers. The homozygous male patient in family 2 also showed a severe phenotype. This finding is intriguing, as to our knowledge, it is the first such report for a male FXII-HAE mutation carrier. In the rare instances in which male mutation carriers are affected, a mild phenotype is typical. The present findings therefore suggest that homozygous FXII-HAE mutation status leads to a severe phenotype in females and males, and to an increased risk of manifest symptoms in the latter.

Optimizing hereditary angioedema management through tailored treatment approaches

Hereditary angioedema (HAE) is a rare but serious and potentially life threatening autosomal dominant condition caused by low or dysfunctional C1 esterase inhibitor (C1-INH) or uncontrolled contact pathway activation. Symptoms are characterized by spontaneous, recurrent attacks of subcutaneous or submucosal swellings typically involving the face, tongue, larynx, extremities, genitalia or bowel. The prevalence of HAE is estimated to be 1:50,000 without known racial differences. It causes psychological stress as well as significant socioeconomic burden. Early treatment and prevention of attacks are associated with better patient outcome and lower socioeconomic burden. New treatments and a better evidence base for management are emerging which, together with a move from hospital-centered to patient-centered care, will enable individualized, tailored treatment approaches.

C1 inhibitor function using contact-phase proteases as target: evaluation of an innovative assay

BACKGROUND

Controlling prekallikrein activation by C1 inhibitor (C1Inh) represents the most essential mechanism for angioedema patient protection. C1Inh function in the plasma is usually measured based on the residual activity of the C1s protease not involved in the pathological process. We have hereby proposed an alternative enzymatic measurement of C1Inh function based on contact-phase activation and correlation with angioedema diagnostic requirements.

METHODS

The contact phase was reconstituted using the purified components, with C1Inh standard or plasma sample. The kinetics of the amidase activity were monitored using Pro-Phe-Arg-pNA, independently of alpha2-macroglobulin. We prevented any interference from a possible high plasma kininogenase activity by preincubating the samples with protease inhibitor. Receiver operating characteristics (ROC) were used to calculate the assay's diagnostic performance.

RESULTS

The calibration curve was built using C1Inh standard (threshold limit 0.10 × 10(-3) U, i.e., 0.2 pmol), and C1Inh function was quantified in the sample, with a reference interval established based on healthy individuals (n = 281; men: 0.61-1.10 U/ml, median: 0.85 U/ml; women: 0.42-1.08 U/ml, median: 0.74 U/ml). The median values of female donors were lower than those of the others due to estrogen, yet C1Inh function remained within the reference interval. The ROC curve calculation provided the following optimum diagnostic cutoff values: women 0.36 U/ml (area under curve [AUC]: 0.99; sensitivity: 93.48%; specificity: 99.37%); and men 0.61 U/ml (AUC: 1; sensitivity: 100.0%; specificity: 100.0%).

CONCLUSION

The performance outcome provided features suitable for angioedema diagnostic or follow-up. Established by means of the kinin formation process, this assay should be preferred over the method based on a C1s protease target.

Distinct conditions support a novel classification for bradykinin-mediated angio-oedema

BACKGROUND

Angio-oedema (AO) can be attributable to bradykinin (BK) accumulation, as is the case for prototypical hereditary AO (HAO) due to C1 inhibitor (C1-INH) deficiency. However, our clinical experience in a reference centre has shown that some patients display a clinical history suggestive of HAO, but exhibit normal C1-INH function, have no mutation in the causative genes associated with HAO (SERPING1, F12), and report no intake of drugs known to promote AO.

OBJECTIVE

We sought to determine the frequency and distribution of different AO subtypes suspected to be BK-mediated AO (BK-AO) and defined by clinical, history and biological criteria (enzyme activities implicated in BK formation and catabolism).

METHODS

The files of all patients referred to our centre for suspected BK-AO were retrospectively analysed.

RESULTS

The distribution of patients (n = 162) was 16 and 4% with a hereditary deficiency of C1-INH or a gain of factor XII function, respectively, 29% with iatrogenic BK-AO, 21% with non-iatrogenic defective kininase activity and 30% with idiopathic increased kinin formation.

CONCLUSION

BK-AO may be caused by multiple inherited or acquired factors triggering BK accumulation. Therefore, we propose a novel typology for BK-AO based on the imbalance of production/catabolism of BK.

[Biological investigation of kinin-mediated angioedema]

Kinin-mediated angioedema results from accumulation of kinins, vasoactive and vasopermeant peptides, on the vascular endothelium. The disease is characterized by sudden episodes of swelling in the subcutaneous and submucosal tissues; the edema may occur spontaneously or it may be precipitated by triggering factors such as physical or emotional stress, or certain medicines. The characterization of kinin formation and catabolism systems helps improve knowledge of the aetiopathogenic mechanisms involved and provides the basis for classification of kinin-mediated angioedema conditions; thus, we may distinguish between angioedema with C1 inhibitor deficiency, whether inherited or acquired, and angioedema with normal C1 inhibitor activity, associated with increased kinin-forming activity or deficiency in kinin catabolism enzymes. In support of the clinical diagnosis, the physician may request laboratory investigation for a functional and molecular definition of the disease. Laboratory diagnosis is based on the characterization of: (1) kinin production control by C1 inhibitor investigation (function, antigen levels and circulating species); (2) kinin production (kininogenase activity, kininogen cleavage species); and (3) kinin catabolism enzymes (aminopeptidase P, carboxypeptidase N, angiotensin-I converting enzyme and dipeptidyl peptidase IV). An abnormal biological phenotype is supported by examination of susceptibility genes (SERPING1, F12 and XPNPEP2) and mutation segregation in the families.

Frequency of the virilising effects of attenuated androgens reported by women with hereditary angioedema

BACKGROUND

Danazol, a drug extensively used in the management of hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE), has various side effects. This study investigated the virilizing actions of this drug in 31 danazol-treated female patients with HAE-C1-INH. We compared our findings with those of healthy controls and with literature data.

METHODS

The patients were interviewed individually about the type and severity of the virilizing effects, as well as about their satisfaction with danazol therapy.

RESULTS

The average duration of danazol treatment was 10.31 years [2 to 23] and its mean daily dose was 131.7 mg [33 to 200]. The most common adverse effects were hirsutism (n=14), weight gain (n=13), and menstrual disturbances (n=8). The severity of danazol adverse effects did not differ by duration of treatment or by daily drug dose. The mean level of patient satisfaction with the treatment was high. The comparison of age-matched healthy controls and of HAE-C1-INH patients receiving danazol did not demonstrate a statistically higher incidence of any of the monitored symptoms in the danazol group.

CONCLUSIONS

Our findings indicate that long-term danazol treatment - using the lowest effective dose - has only a mild virilizing effect.

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.

Hereditary angioedema: what the gastroenterologist needs to know

Up to 93% of patients with hereditary angioedema (HAE) experience recurrent abdominal pain. Many of these patients, who often present to emergency departments, primary care physicians, general surgeons, or gastroenterologists, are misdiagnosed for years and undergo unnecessary testing and surgical procedures. Making the diagnosis of HAE can be challenging because symptoms and attack locations are often inconsistent from one episode to the next. Abdominal attacks are common and can occur without other attack locations. An early, accurate diagnosis is central to managing HAE. Unexplained abdominal pain, particularly when accompanied by swelling of the face and extremities, suggests the diagnosis of HAE. A family history and radiologic imaging demonstrating edematous bowel also support an HAE diagnosis. Once HAE is suspected, C4 and C1 esterase inhibitor (C1-INH) laboratory studies are usually diagnostic. Patients with HAE may benefit from recently approved specific treatments, including plasma-derived C1-INH or recombinant C1-INH, a bradykinin B2-receptor antagonist, or a kallikrein inhibitor as first-line therapy and solvent/detergent-treated or fresh frozen plasma as second-line therapy for acute episodes. Short-term or long-term prophylaxis with nanofiltered C1-INH or attenuated androgens will prevent or reduce the frequency and severity of episodes. Gastroenterologists can play a critical role in identifying and treating patients with HAE, and should have a high index of suspicion when encountering patients with recurrent, unexplained bouts of abdominal pain. Given the high rate of abdominal attacks in HAE, it is important for gastroenterologists to appropriately diagnose and promptly recognize and treat HAE, or refer patients with HAE to an allergist.

Current update on cellular and molecular mechanisms of hereditary angioedema

OBJECTIVE

To provide an update on the molecular mechanisms of hereditary angioedema (HAE).

DATA SOURCES

MEDLINE and PubMed databases were searched to identify pertinent articles using the following key terms: hereditary angioedema, angioedema, C1 inhibitor, bradykinin, contact system, factor XII, mechanism, pathophysiology, severity, permeability, and estrogen.

STUDY SELECTIONS

Articles were selected based on their relevance to the subject matter.

RESULTS

Although the biochemical basis of "classic" HAE is known to result from C1 esterase inhibitor (C1INH) deficiency, a new form, HAE with normal C1INH, has been identified. HAE types I and II are caused by mutations in the SERPING1 gene that result in decreased plasma levels of functional C1INH. In HAE with normal C1INH, mutations in the F12 gene have been identified in a subset of individuals, but the genetic defect remains unknown in most patients. The primary mediator of swelling in HAE is bradykinin, a product of the plasma contact system that increases vascular permeability. HAE disease severity is highly variable and may be influenced by polymorphisms in other genes and other factors, such as hormones, trauma, stress, and infection.

CONCLUSION

Hereditary angioedema is a heterogeneous disorder with a complex pathophysiology. Implicated genes include SERPING1 and FXII in patients with HAE from C1INH deficiency and HAE with normal C1INH levels, respectively. Disease severity is highly variable.

Update on preventive therapy (prophylaxis) for hereditary angioedema

Both prophylactic and acute treatment of hereditary angioedema have been revolutionized in the past decade. Effective prophylactic treatment has long been provided by the group of attenuated androgens and antifibrinolytic agents, but their use has been attended by side effects. Plasma derived C1 inhibitor has been added to the group of agents effective in prophylaxis and a group of agents, discussed elsewhere in this volume, has been added to the armamentarium for acute therapy.