Mutational Spectrum of the C1 Inhibitor Gene in a Cohort of Italian Patients with Hereditary Angioedema: Description of Nine Novel Mutations

Plasma microRNAs as biomarkers in hereditary angioedema

BACKGROUND

Hereditary angioedema (HAE) is an autosomal dominant disease with variable expression. In some families with identical genetic abnormalities, the expression can range from several attacks per month to no attacks at all. It is hypothesized that post-transcriptional gene regulation accounts for the variable expression of the disease.

OBJECTIVE

To identify candidate microRNAs (miRNAs) that could play a role in HAE by determining whether miRNAs are differentially expressed in patients with HAE vs non-HAE individuals and whether expression profiles are tracked with severity.

METHODS

This study compared serum miRNA expression in patients with HAE vs non-HAE using RNA sequencing. Associations between miRNA expression and HAE severity were assessed in patients with mild disease (<6 attacks a year) vs severe disease (>1 attack per month). The functions of candidate miRNAs were analyzed using in silico methods.

RESULTS

There were robust miRNA expression differences between patients with HAE and non-HAE controls. A cluster analysis identified subgroups of patients with HAE having unique miRNA profiles that tracked with frequency of attacks. Two miRNAs, miR-99b-5p and miR-127-3p, were differentially expressed between mild and severe HAE (adjusted P < .05). In silico analysis revealed a function of differentially expressed miRNAs in regulation of C1 esterase inhibitor, kininogen, the bradykinin B2 receptor, and adherens junction function.

CONCLUSION

Candidate microRNAs were identified that could distinguish patients with and without HAE and may be used to identify phenotypes of HAE.

Complex analysis of the national Hereditary angioedema cohort in Slovakia - Identification of 12 novel variants in SERPING1 gene

Background

Hereditary angioedema (HAE) is a rare autosomal dominant genetic disease characterised by acute episodes of non-pruritic skin and submucosal swelling caused by increase in vascular permeability.

Objective

Here we present the first complex analysis of the National HAE Slovakian cohort with the detection of 12 previously un-published genetic variants in SERPING1 gene.

Methods

In patients diagnosed with hereditary angioedema caused by deficiency or dysfunction of C1 inhibitor (C1-INH-HAE) based on clinical manifestation and complement measurements, SERPING1 gene was tested by DNA sequencing (Sanger sequencing/massive parallel sequencing) and/or multiplex ligation-dependent probe amplification for detection of large rearrangements.

Results

The Slovakian national cohort consisted of 132 living patients with confirmed HAE. We identified 51 index cases (32 families, 19 sporadic patients/112 adults, 20 children). One hundred seventeen patients had HAE caused by deficiency of C1 inhibitor (C1-INH-HAE-1) and 15 patients had HAE caused by dysfunction of C1 inhibitor (C1-INH-HAE-2). The prevalence of HAE in Slovakia has recently been calculated to 1:41 280 which is higher than average calculated prevalence. The estimated incidence was 1:1360 000. Molecular-genetic testing of the SERPING1 gene found 22 unique causal variants in 26 index cases, including 12 previously undescribed and unreported.

Conclusion

The first complex report about epidemiology and genetics of the Slovakian national HAE cohort expands the knowledge of the C1-INH-HAE genetics. Twelve novel causal variants were present in the half of the index cases. A higher percentage of inframe variants comparing to other studies was observed. Heterozygous deletion of exon 3 found in a large C1-INH-HAE-1 family probably causes the dysregulation of the splicing isoforms balance and leads to the decrease of full-length C1-INH level.

Restriction of C1-inhibitor activity in hereditary angioedema by dominant-negative effects of disease-associated SERPING1 gene variants

BACKGROUND

Patients with hereditary angioedema experience recurrent, sometimes life-threatening, attacks of edema. It is a rare genetic disorder characterized by genetic and clinical heterogenicity. Most cases are caused by genetic variants in the SERPING1 gene leading to plasma deficiency of the encoded protein C1 inhibitor (C1INH). More than 500 different hereditary angioedema-causing variants have been identified in the SERPING1 gene, but the disease mechanisms by which they result in pathologically low C1INH plasma levels remain largely unknown.

OBJECTIVES

The aim was to describe trans-inhibitory effects of full-length or near full-length C1INH encoded by 28 disease-associated SERPING1 variants.

METHODS

HeLa cells were transfected with expression constructs encoding the studied SERPING1 variants. Extensive and comparative studies of C1INH expression, secretion, functionality, and intracellular localization were carried out.

RESULTS

Our findings characterized functional properties of a subset of SERPING1 variants allowing the examined variants to be subdivided into 5 different clusters, each containing variants sharing specific molecular characteristics. For all variants except 2, we found that coexpression of mutant and normal C1INH negatively affected the overall capacity to target proteases. Strikingly, for a subset of variants, intracellular formation of C1INH foci was detectable only in heterozygous configurations enabling simultaneous expression of normal and mutant C1INH.

CONCLUSIONS

We provide a functional classification of SERPING1 gene variants suggesting that different SERPING1 variants drive the pathogenicity through different and in some cases overlapping molecular disease mechanisms. For a subset of gene variants, our data define some types of hereditary angioedema with C1INH deficiency as serpinopathies driven by dominant-negative disease mechanisms.

Innate Immunity: A Balance between Disease and Adaption to Stress

Since first being documented in ancient times, the relation of inflammation with injury and disease has evolved in complexity and causality. Early observations supported a cause (injury) and effect (inflammation) relationship, but the number of pathologies linked to chronic inflammation suggests that inflammation itself acts as a potent promoter of injury and disease. Additionally, results from studies over the last 25 years point to chronic inflammation and innate immune signaling as a critical link between stress (exogenous and endogenous) and adaptation. This brief review looks to highlight the role of the innate immune response in disease pathology, and recent findings indicating the innate immune response to chronic stresses as an influence in driving adaptation.

The place of scales and questionnaires in assessing the disease’s severity and the long-term prophylaxis’s prescribing in patients with hereditary angioedema

Hereditary angioedema is a hereditary life-threatening disease characterized by recurrent angioedema of various strength and localization. To date, definite diseases severity criteria have not been developed. There are many different factors to consider not only the frequency of episodes, but also their duration, strength, influence on the patient's appearance, the severity of the pain syndrome. Disease related quality of life, the number of work disability days, and the patient's satisfaction with the prescribed treatment are important. In addition, there are no criteria for prescribing long-term prophylaxis, and no parameters for choosing a specific drug. The introduction of specific scales and questionnaires developed to assess such characteristics as disease activity, disease control, quality of life in patients with recurrent angioedema into clinical practice seems to be the best solution for both questions. The comprehensive understanding of the diseases severity in a particular patient can be carried out with the combined use of assessment tools.

The importance of recognizing and managing a rare form of angioedema: hereditary angioedema due to C1-inhibitor deficiency

The majority of angioedema cases encountered in clinical practice are histamine-mediated (allergic); however, some cases are bradykinin-related (non-allergic) and do not respond to standard anti-allergy medications. Among bradykinin-related angioedema, hereditary angioedema (HAE) is a rare, but chronic and debilitating condition. The majority of HAE is caused by deficiency (type 1) or abnormal function (type 2) of the naturally occurring protein, C1-inhibitor (C1-INH)-a major inhibitor of proteases in the contact (kallikrein-bradykinin cascade), fibrinolytic pathway, and complement systems. Failure to recognize HAE and initiate appropriate intervention can lead to years of pain, disability, impaired quality of life (QoL) and, in cases of laryngeal involvement, it can be life-threatening. HAE must be considered in the differential diagnosis of non-urticarial angioedema, particularly for patients with a history of recurrent angioedema attacks, family history of HAE, symptom onset in childhood/adolescence, prodromal signs/symptoms before swellings, recurrent/painful abdominal symptoms, and upper airway edema. Management strategies for HAE include on-demand treatment for acute attacks, short-term prophylaxis prior to attack-triggering events/procedures, and long-term or routine prophylaxis for attack prevention. Patients should be evaluated at least annually to assess need for routine prophylaxis. HAE specific medications like plasma-derived and recombinant C1-INH products, kallikrein inhibitors, and bradykinin B2 receptor antagonists, have improved management of HAE. While the introduction of intravenous C1-INH represented a major breakthrough in routine HAE prophylaxis, some patients fail to achieve adequate control and others have psychological barriers or experience complications related to intravenous administration. Subcutaneous (SC) C1-INH, SC monoclonal antibody (mAb)-based therapies, and an oral kallikrein inhibitor offer effective alternatives for HAE attack prevention and may facilitate self-administration. HAE management should be individualized, with QoL improvement being a key goal. This can be achieved with broader availability of existing options for routine prophylaxis, including greater global availability of C1-INH(SC), mAb-based therapy, oral treatments, and multiple on-demand therapies.

Gastrointestinal manifestations of angioedema: a potential area of misdiagnosis

Abdominal pain is one of the most common conditions leading people to the emergency department. An uncommon but well described cause of abdominal pain is angioedema of the gastrointestinal tract due to recurrent angioedema without wheals. Abdominal involvement is very common in hereditary angioedema (HAE), but it is also described in acquired angioedema and allergic forms. In patients with HAE, the involvement of gastrointestinal tract with resultant abdominal pain occurs in 43-93% of cases. Attacks can involve the entire gastrointestinal tract, such as the oropharynx, small intestine, colon, liver, or pancreas. Pain is the most common gastrointestinal symptom, and it may occur for many years even without cutaneous or respiratory symptoms. The case report we included in this article emphasizes the importance of accurate evaluation of personal and family history in patients with a long history of acute, severe, and unexplained abdominal pain, and it gives an example of how diagnostic delay may be longer if gastroenterological symptoms are the predominant clinical presentation. Furthermore, sometimes the simultaneous presence of concomitant gastrointestinal disorders and HAE may cause difficulties in differential diagnosis. Gastroenterologists and other physicians should add HAE to their list of potential causes of unexplained abdominal pain. The initiation of appropriate prophylaxis and treatment will prevent needless suffering and useless surgical and medical procedures.

Novel SERPING1 gene mutations and clinical experience of type 1 hereditary angioedema from North India

BACKGROUND

There is paucity of literature on long-term follow-up of patients with hereditary angioedema (HAE) from developing countries.

OBJECTIVE

This study was carried out to analyze the clinical manifestations, laboratory features, and genetic profile of 32 patients (21 male and 11 female) from 23 families diagnosed with HAE between January 1996 and December 2019.

METHODS

Data were retrieved from medical records of Paediatric Immunodeficiency Clinic, Postgraduate Institute of Medical Education and Research, Chandigarh, India.

RESULTS

Median age at onset of symptoms was 6.25 years (range 1-25 years), and median age at diagnosis was 12 years (range 2-43 years). Serum complement C4 level was decreased in all patients. All patients had low C1-esterase inhibitor (C1-INH) quantitative level (type 1 HAE). SERPING1 gene sequencing could be carried out in 20 families. Of these, 11 were identified to have a pathogenic disease-causing variant in the SERPING1 gene. While 2 of these families had a previously reported mutation, remaining 9 families had novel pathogenic variants in SERPING1 gene. Because of non-availability of C1-INH therapy in India, all patients were given long-term prophylaxis (attenuated androgens or tranexamic acid (TA) or a combination of the 2). Life-threatening episodes of laryngeal edema were managed with fresh-frozen plasma (FPP) infusions. We recorded one disease-related mortality in our cohort. This happened in spite of long-term prophylaxis with stanozolol and TA.

CONCLUSIONS

We report largest single-center cohort of patients with HAE from India. Attenuated androgens, fibrinolytic agents, and FPP may be used for management of HAE in resource-limited settings.

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.

Role of Endothelial G Protein-Coupled Receptor Kinase 2 in Angioedema

Excessive BK (bradykinin) stimulation is responsible for the exaggerated permeabilization of the endothelium in angioedema. However, the molecular mechanisms underlying these responses have not been investigated. BK receptors are Gq-protein-coupled receptors phosphorylated by GRK2 (G protein-coupled receptor kinase 2) with a hitherto unknown biological and pathophysiological significance. In the present study, we sought to identify the functional role of GRK2 in angioedema through the regulation of BK signaling. We found that the accumulation of cytosolic Ca²⁺ in endothelial cells induced by BK was sensitive to GRK2 activity, as it was significantly augmented by inhibiting the kinase. Accordingly, permeabilization and NO production induced by BK were enhanced, as well. In vivo, mice with reduced GRK2 levels in the endothelium (Tie2-CRE/GRK2^fl+/fl-) exhibited an increased response to BK in terms of vascular permeability and extravasation. Finally, patients with reduced GRK2 levels displayed a severe phenotype of angioedema. Taken together, these findings establish GRK2 as a novel pivotal regulator of BK signaling with an essential role in the pathophysiology of vascular permeability and angioedema.

Impaired control of the contact system in hereditary angioedema with normal C1-inhibitor

BACKGROUND

Hereditary angioedema (HAE) comprises HAE with C1-inhibitor deficiency (C1-INH-HAE) and HAE with normal C1-INH activity (nl-C1-INH-HAE), due to mutations in factor XII (FXII-HAE), plasminogen (PLG-HAE), angiopoietin 1 (ANGPT1-HAE), kininogen 1 genes (KNG1-HAE), or angioedema of unknown origin (U-HAE). The Italian network for C1-INH-HAE (ITACA) created a registry including different forms of angioedema without wheals.

OBJECTIVE

We analyzed clinical and laboratory features of a cohort of Italian subjects with nl-C1-INH-HAE followed by ITACA to identify specific biomarkers.

METHODS

A total of 105 nl-C1-INH-HAE patients were studied. Plasma concentrations of cleaved high-molecular-weight kininogen (cHK), vascular endothelial growth factors (VEGFs), angiopoietins (Angs), and secreted phospholipase A₂ enzymes (sPLA₂ ) were evaluated.

RESULTS

We identified 43 FXII-HAE patients, 58 U-HAE, and 4 ANGPT1-HAE. We assessed a prevalence of 1:1.4 × 10⁶ for FXII-HAE and 1:1.0 × 10⁶ for U-HAE. cHK levels in U-HAE patients were similar to controls in plasma collected using protease inhibitors cocktail (PIC), but they significantly increased in the absence of PIC. In FXII-HAE patients, cHK levels, in the absence of PIC, were significantly higher than in controls. We found a significant increase of VEGF-A, VEGF-C, and Ang1 levels in U-HAE patients compared to controls. In FXII-HAE, only VEGF-C levels were increased. Ang2 concentrations and sPLA₂ activity were not modified. The levels of these mediators in ANGPT1-HAE patients were not altered.

CONCLUSIONS

Our results suggest that pathogenesis of FXII-, ANGPT1-, and U-HAE moves through an unbalanced control of kallikrein activity, with bradykinin as most likely mediator. VEGFs and Ang1 participate in the pathophysiology of U-HAE increasing the basal vascular permeability.

The signal peptide as a new target for drug design

Many current and potential drug targets are membrane-bound or secreted proteins that are expressed and transported via the Sec61 secretory pathway. They are targeted to translocon channels across the membrane of the endoplasmic reticulum (ER) by signal peptides (SPs), which are temporary structures on the N-termini of their nascent chains. During translation, such proteins enter the lumen and membrane of the ER by a process known as co-translational translocation. Small molecules have been found that interfere with this process, decreasing protein expression by recognizing the unique structures of the SPs of particular proteins. The SP may thus become a validated target for designing drugs for numerous disorders, including certain hereditary diseases.

Deep Intronic Mutation in SERPING1 Caused Hereditary Angioedema Through Pseudoexon Activation

PURPOSE

Hereditary angioedema (HAE) is a rare autosomal dominant life-threatening disease characterized by low levels of C1 inhibitor (type I HAE) or normal levels of ineffective C1 inhibitor (type II HAE), typically occurring as a consequence of a SERPING1 mutation. In some cases, a causal mutation remains undetected after using a standard molecular genetic analysis.

RESULTS

Here we show a long methodological way to the final discovery of c.1029 + 384A > G, a novel deep intronic mutation in intron 6 which is responsible for HAE type I in a large family and has not been identified by a conventional diagnostic approach. This mutation results in de novo donor splice site creation and subsequent pseudoexon inclusion, the mechanism firstly described to occur in SERPING1 in this study. We additionally discovered that the proximal part of intron 6 is a region potentially prone to pseudoexon-activating mutations, since natural alternative exons and additional cryptic sites occur therein. Indeed, we confirmed the existence of at least two different alternative exons in this region not described previously.

CONCLUSIONS

In conclusion, our results suggest that detecting aberrant transcripts, which are often low abundant because of nonsense-mediated decay, requires a modified methodological approach. We suggest SERPING1 intron 6 sequencing and/or tailored mRNA analysis to be routinely used in HAE patients with no mutation identified in the coding sequence.

Mutational spectrum and genotype-phenotype relationships in a cohort of Romanian hereditary angioedema patients caused by C1 inhibitor deficiency

Background: Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) caused by SERPING1 mutations is a rare monogenic disorder characterized by a high frequency of de novo mutations, allelic heterogeneity and populational differences. Geno- and phenotype correlation data are limited. Addressing the pathogenic complexity, we proposed to analyze the clinical and genetic characteristics in a set of Romanian patients. Material and Methods: 49 patients from 22 unrelated families with C1-INH-HAE were investigated, by calculating clinical severity score (CSS), C1-INH and C4 level assessment by nephelometric assays, C1-INH function study by functional enzyme-linked immunosorbent assay, and mutation analysis by sequencing and MLPA. Clinical manifestations by missense vs other mutation mechanisms were compared. Results: The mean age at diagnosis and onset was 28.8±14.7 and 15.1±15.2 years, while the diagnostic delay 13.1±10.1 years. CSS ranged from 2 to 9, with a mean of 5.4±1.8. The frequency of missense and nonsense mutations, splice defects, frameshift mutations and large gene rearrangements was 61.22, 6.12, 22.4, 6.12 and 4.08%; in the regulatory sequence no mutation was described. In type II, only missense mutations were noted. Lower levels of C1-INH characterized index cases caused by mechanisms other than missense mutation, with more severe consequences on protein synthesis (p=0.017). 53% of the cases were identified by familial screening. Conclusion: A later onset of disease manifestations and a higher frequency of missense mutations characterize HAE in Romanian patients with SERPING1 mutation. Genetic analysis improves the management of affected families, and may inform about disease severity.

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.

SERPING1 exon 3 splicing variants using alternative acceptor splice sites

Mutations in the C1 inhibitor (C1INH) encoding gene, SERPING1, are associated with hereditary angioedema (HAE) which manifests as recurrent submucosal and subcutaneous edema episodes. The major C1INH function is the complement system inhibition, preventing its spontaneous activation. The presented study is focused on SERPING1 exon 3, an alternative and extraordinarily long exon (499 bp). Endogenous expression analysis performed in the HepG2, human liver, and human peripheral blood cells revealed several exon 3 splicing variants alongside exon inclusion: a highly prevalent exon skipping variant and less frequent +38 and -15 variants with alternative 3' splice sites (ss) located 38 and 15 nucleotides downstream and upstream from the authentic 3' ss, respectively. An exon skipping variant introducing a premature stop codon, represented nearly one third of all splicing variants and surprisingly appeared not to be degraded by NMD. The alternative -15 3' ss was used to a small extent, although predicted to be extremely weak. Its use was shown to be independent of its strength and highly sensitive to any changes in the surrounding sequence. -15 3' ss seems to be co-regulated with the authentic 3' ss, whose use is dependent mainly on its strength and less on the presence of intronic regulatory motifs. Subtle SERPING1 exon 3 splicing regulation can contribute to overall C1INH plasma levels and HAE pathogenesis.

Oxidative stress markers in patients with hereditary angioedema

INTRODUCTION

Hereditary angioedema due to C1-INH deficiency (C1-INH-HAE) or with normal C1-INH is characterized by recurrent swellings due to uncontrolled production of vasoactive mediators, among which bradykinin (BK) is crucial. Through the binding and activation of the two human BK-receptors, kinins may have dual beneficial and deleterious effects in vascular and inflammation physiopathology by inducing oxidative stress. We aimed to assess the serum concentrations of advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs) in patients affected by HAE.

MATERIAL AND METHODS

Blood samples were collected to measure the serum concentrations of AGEs and AOPPs by spectrofluorimetric and spectrophotometric methods in patients affected by C1-INH-HAE and FXII-HAE during the remission state.

RESULTS

We showed that the circulating levels of AOPPs observed on control group (0.94 (0.36) nmol/mg) were significantly lower than those observed on the C1-INH-HAE group (1.68 (0.47) nmol/mg; p = 0.002) and FXII-HAE (1.50 (0.27) nmol/mg; p = 0.001). Moreover, the circulating levels of AGEs were significantly higher in C1-INH-HAE group (211.58 (151.05) AU/g; p = 0.02) than the FXII group (141.48 (89.59) AU/g), thus demonstrating a state of heightened oxidative stress.

CONCLUSIONS

Our observations show additional underlying events involved in HAE and are of central importance for further investigations of differences in bradykinin receptors signaling among the two disease subgroups.

Deletions in SERPING1 Lead to Lower C1 Inhibitor Function: Lower C1 Inhibitor Function Can Predict Disease Severity

BACKGROUND

How genotype affects phenotype in hereditary angioedema with C1 inhibitor deficiency (C1-INH-HAE) has not been totally clarified. In this study, we investigated the relationship between different types of mutations and various phenotypic characteristics.

METHODS

Clinical data from 81 patients from 47 families were recorded. Complement proteins were analyzed from 61 untreated patients. The coding exons and the exon-intron boundaries of the SERPING1 gene were sequenced, and deletion/duplication analysis with multiple ligation dependent probe amplification was performed. The relationship of complement protein with the mutation type was analyzed by using generalized estimating equations.

RESULTS

Thirty-five different mutations (15 novel and 2/15 homozygous) were identified. There was no causative mutation in 6 patients (7.4%). Patients with deletion and large deletion had the lowest (5.05%, 0-18.7; 5.8%, 0-16.5%, respectively), and the none mutation group had the highest C1 inhibitor function (23.3%, 11-78%, p < 0.001). C1 inhibitor function levels decreased as the age of the disease progressed (r = -0.352, p = 0.005). Lower C1 inhibitor function levels caused severer disease (r = -0.404, p = 0.001) and more frequent annual attacks (r = -0.289, p = 0.024). In the off-attack period, C1q levels were lower than normal in 9.8% of the patients.

CONCLUSION

Deletion mutations may represent the most unfavorable effect on C1 inhibitor function. The earlier disease onset age could be a sign for lower C1 inhibitor function levels in adult life. C1q levels could also be low in C1-INH-HAE patients, as in acquired angioedema. Lower C1 inhibitor function can predict disease severity and may have negative impacts on the course of C1-INH-HAE.

Targeted next-generation sequencing for the molecular diagnosis of hereditary angioedema due to C1-inhibitor deficiency

SERPING1 genotyping of subjects suspicious for hereditary angioedema due to C1-INH deficiency (C1-INH-HAE) is important for clinical practice as well as for research reasons. Conventional approaches towards the detection of C1-INH-HAE-associated SERPING1 variants are cumbersome and time-demanding with many pitfalls. To take advantage of the benefits of next-generation sequencing (NGS) technology, we developed and validated a custom NGS platform that, by targeting the entire SERPING1 gene, facilitates genetic testing of C1-INH-HAE patients in clinical practice. In total, 135 different C1-INH-HAE-associated SERPING1 variants, out of the approximately 450 reported, along with 115 negative controls and 95 randomly selected DNA samples from affected family members of C1-INH-HAE index patients, were included in the forward and reverse validation processes of this platform. Our platform's performance, i.e. analytical sensitivity of 98.96%, a false negative rate of 1.05%, analytical specificity 100%, a false positive rate equal to zero, accuracy of 99.35%, and repeatability of 100% recommends its implementation as a first line approach for the genetic testing of C1-INH-HAE patients or as a confirmatory method. A noteworthy advantage of our platform is the concomitant detection of single nucleotide variants and copy number variations throughout the whole length of the SERPING1 gene, moreover providing information about the size and the localization of the latter. During our study, 15 novel C1-INH-HAE-related SERPING1 variants were detected.

Hereditary angioedema due to C1-inhibitor deficiency in Macedonia: clinical characteristics, novel SERPING1 mutations and genetic factors modifying the clinical phenotype

OBJECTIVE

Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare disease, characterized by swellings. We aimed to characterize on a clinical and molecular basis C1-INH-HAE patients in the Republic of Macedonia.

RESULTS

All 15 patients from six unrelated families were diagnosed with C1-INH-HAE type I, with a mean age of symptom onset of 11 years and an average delay of diagnosis of seven years. Patients reported on average 31 angioedema attacks/year, with a median clinical severity score (CSS) of 7. We identified three known mutations and two new mutations (c.813_818delCAACAA and c.1488T > G) that were reported for the first time. To address the genotype-phenotype association, a pooled analysis including 78 C1-INH-HAE south-eastern European patients was performed, with additional analysis of F12-46C/T and KLKB1-428G/A polymorphisms. We demonstrated that patients with nonsense and frameshift mutations, large deletions/insertions, splicing defects and mutations at Arg444 exhibited an increased CSS compared with missense mutations, excluding mutations at Arg444. In addition, the CC F12-46C/T polymorphism was suggestive of earlier disease onset.

DISCUSSION

Genetic analysis helped identify the molecular basis of C1-INH-HAE given that causative mutations in SERPING1 were detected in all patients, including an infant before the appearance of clinical symptoms. We identified two novel mutations and further corroborated the genotype-phenotype relationship, wherein mutations with a clear effect on C1-INH function predispose patients to a more severe disease phenotype and CC F12-46C/T predisposes patients to earlier disease onset. KEY MESSAGES • In the present nationwide study, we aimed to characterize on a clinical and molecular basis patients with hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) in the Republic of Macedonia.   • Causative mutations in SERPING1 were detected in all 15 C1-INH-HAE patients from six Macedonian families, including an infant, before the appearance of clinical symptoms.   • We identified three known mutations and two novel mutations (c.813_818delCAACAA and c.1488T > G). These findings further corroborated the genotype-phenotype relationship, wherein mutations with a clear effect on C1-INH function predispose patients to a more severe disease phenotype and the CC F12-46C/T polymorphism predisposes patients to earlier disease onset.

Personalized Medicine in Allergy

Allergic disease is among the most common pathologies worldwide and its prevalence has constantly increased up to the present days, even if according to the most recent data it seems to be slightly slowing down. Allergic disease has not only a high rate of misdiagnosis and therapeutic inefficacy, but represents an enormous, resource-absorbing black hole in respiratory and general medicine. The aim of this paper is to summarize principal therapeutic innovations in atopic disease management befallen in the recent years in terms of personalized/precision medicine.

Frequent life-threatening laryngeal attacks in two Croatian families with hereditary angioedema due to C1 inhibitor deficiency harbouring a novel frameshift mutation in SERPING1

OBJECTIVE

Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare autosomal dominant disease caused by mutations in the SERPING1 gene. It can affect many regions in the body, but potentially life-threatening laryngeal oedemas are of concern.

METHODS

Twenty-three subjects from two families were recruited for clinical data evaluation and molecular analysis at General Hospital Šibenik, Croatia.

RESULTS

Decreased levels of C1 inhibitor were detected in 12 adult patients and three young asymptomatic persons. The same novel deletion of two nucleotides on exon 3 (c.74_75delAT) was identified in all of them. A history of laryngeal oedema was present in 10 patients (83%), and all patients reported laryngeal attacks at least once a year. The delay in diagnosis decreased noticeably from the first to the last generation.

CONCLUSIONS

We identified a novel causative mutation in SERPING1 in several affected members of two apparently unrelated families with a high frequency of laryngeal oedema. Molecular analysis of large C1-INH-HAE families will provide new insights on the genotype-phenotype relationship. Key messages Hereditary angioedema due to C1 inhibitor deficiency is a rare autosomal dominant disease caused by mutations in the SERPING1 gene, and laryngeal oedema is of concern because it can cause death by asphyxiation. A novel causative mutation in SERPING1, a deletion of two nucleotides on exon 3 (c.74_75delAT), was identified in several affected members of two apparently unrelated families with a high frequency of laryngeal oedema. Molecular analysis of large C1-INH-HAE families will provide new insights on the genotype-phenotype relationship because it appears that the mutation type may affect disease severity.

Elevated plasma levels of vascular permeability factors in C1 inhibitor-deficient hereditary angioedema

BACKGROUND

Hereditary angioedema with C1 inhibitor deficiency (C1-INH-HAE) is a rare inherited genetic disease characterized by recurrent swelling episodes of the skin, gastrointestinal tract, and upper airways. Angioedema attacks result from increased vascular permeability due to the release of bradykinin from high molecular weight kininogen. Currently, there are no biomarkers predicting the frequency of angioedema attacks. Vascular permeability is modulated by several factors, including vascular endothelial growth factors (VEGFs) and angiopoietins (Angs). As increased circulating levels of VEGFs and Angs have been observed in diseases associated with higher vascular permeability (e.g., systemic capillary leak syndrome and sepsis), we sought to analyze plasma concentrations of VEGFs and Angs in patients with C1-INH-HAE.

METHODS

Sixty-eight healthy controls and 128 patients with C1-INH-HAE were studied. Concentrations of angiogenic (VEGF-A, Ang1, Ang2), anti-angiogenic (VEGF-A165b ) and lymphangiogenic (VEGF-C) factors were evaluated by ELISA. C1-INH functional activity was assessed by EIA.

RESULTS

Plasma concentrations of VEGF-A, VEGF-C, Ang1, and Ang2 were higher in patients with C1-INH-HAE in remission than in healthy controls. Concentration of VEGF-A was further increased in patients with lower C1-INH functional activity. Patients with C1-INH-HAE experiencing more than 12 angioedema attacks per year were characterized by higher plasma levels of VEGF-A, VEGF-C, and Ang2 compared with the other patients.

CONCLUSIONS

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

Diagnostic and therapeutic management of hereditary angioedema due to C1-inhibitor deficiency: the Italian experience

PURPOSE OF REVIEW

Hereditary angioedema (HAE) due to C1-inhibitor (C1-INH) deficiency (C1-INH-HAE) is a rare disease, with a reported prevalence of about 1 : 50 000. C1-INH-HAE causes disabling symptoms, which may be life-threatening if swelling affects upper airways. Diagnostic procedures are now well established and the role of bradykinin as the main mediator of plasma outflow eliciting angioedema formation has been clearly elucidated.

RECENT FINDINGS

Increased understanding of the pathogenesis of C1-INH-HAE allowed in recent years the development of new drugs targeted to inhibit bradykinin synthesis (Ecallantide) or activity (Icatibant). At the same time, a recombinant C1-INH concentrate (Ruconest) was produced from the milk of transgenic rabbits and two plasma-derived C1-INHs (Berinert, Cinryze) underwent controlled trials to obtain marketing authorization. In 2012, an Italian network for C1-INH-HAE (ITACA) was established by physicians of 17 HAE reference centres to collect data from Italian patients and to homogenize and improve the diagnostic and therapeutic approach to the disease.

SUMMARY

Although there is a widespread agreement on therapeutic goals and treatment of C1-INH-HAE acute attacks, different approaches to prophylaxis are still present among HAE experts. The clinical experience of ITACA on a large population of C1-INH-HAE patients followed for several years may help in identifying the most effective strategies for the management of the disease.

Hereditary Angioedema Due to C1 Inhibitor Deficiency in Serbia: Two Novel Mutations and Evidence of Genotype-Phenotype Association

Hereditary angioedema due to C1 inhibitor deficiency (C1-INH-HAE) is a rare autosomal dominant disease characterized by recurrent life-threatening oedemas and/or abdominal pain and caused by mutations affecting the C1 inhibitor gene, SERPING1. We sought to investigate the spectrum of SERPING1 mutations in Serbia and the possible genotype-phenotype association. C1-INH-HAE was diagnosed on the basis of clinical and laboratory criteria in 40 patients from 27 families; four were asymptomatic. Mutational analysis of the SERPING1 gene was performed by sequencing and multiplex ligation-dependent probe amplification. Disease-causing mutations in SERPING1 were identified in all patients. In C1-INH-HAE type I, we identified 19 different mutations, including 6 missense mutations, 6 nonsense mutations, 2 small deletions, 1 small insertion, 2 splicing defects and 2 large deletions. Two of the mutations (c.300C>T and c.1184_1185insTA) are reported here for the first time. All C1-INH-HAE type II patients from three families harboured the same substitution (c.1396C>T). Based on the type of mutation identified in the SERPING1 gene, patients were divided into two groups: group 1 (nonsense, frameshift, large deletions/insertions, splicing defect, and mutations at Arg444) or group 2 (missense, excluding mutations at Arg444). Significant differences were found in the clinical severity score (P = 0.005), prevalence of laryngeal (P = 0.040) and facial (P = 0.013) oedema, and long-term prophylaxis (P = 0.023) between the groups with different types of mutations. Because our population consisted of related subjects, differences in the severity score between mutation groups were further confirmed using the generalized estimating equation (P = 0.038). Our study identified 20 different disease-causing mutations, including two novel mutations, in all C1-INH-HAE patients, highlighting the heterogeneity of mutations in the SERPING1 gene. Furthermore, it appears that mutations with a clear effect on C1-INH function might be responsible for a more severe disease phenotype.

A Nationwide Study of Norwegian Patients with Hereditary Angioedema with C1 Inhibitor Deficiency Identified Six Novel Mutations in SERPING1

Hereditary angioedema with C1 inhibitor deficiency (C1-INH-HAE) is characterized by relapsing, non-pruritic swelling in skin and submucosal tissue. Symptoms can appear in early infancy when diagnosis is more difficult. In the absence of a correct diagnosis, treatment of abdominal attacks often lead to unnecessary surgery, and laryngeal edema can cause asphyxiation. A cohort study of 52 patients from 25 unrelated families in Norway was studied. Diagnosis of C1-INH-HAE was based on international consensus criteria including low functional and/or antigenic C1-INH values and antigenic C4. As SERPING1 mutations in Norwegian patients with C1-INH-HAE are largely undescribed and could help in diagnosis, we aimed to find and describe these mutations. Mutation analysis of the SERPING1 gene was performed by Sanger sequencing of all protein coding exons and exon-intron boundaries. Samples without detected mutation were further analyzed by multiplex ligation-dependent probe amplification to detect deletions and duplications. Novel mutations suspected to lead to splice defects were analyzed on the mRNA level. Fifty-two patients from 25 families were included. Forty-four (84,6%) suffered from C1-INH-HAE type I and eight (15,4%) suffered from C1-INH-HAE type II. Pathogenic or likely pathogenic mutations were found in 22/25 families (88%). Thirteen unique mutations were detected, including six previously undescribed. There were three missense mutations including one mutation affecting the reactive center loop at codon 466, three nonsense mutations, three small deletions/duplications, three gross deletions, and one splice mutation.

Characterization of patients with angioedema without wheals: the importance of F12 gene screening

Sporadic and familiar forms of non-histaminergic angioedema and normal C1 inhibitor encompass a group of disorders possibly caused by bradikinin. We aimed to study the subgroups of hereditary angioedema with FXII mutation (FXII-HAE), unknown genetic defect (U-HAE) and idiopathic non-histaminergic acquired angioedema (InH-AAE). We screened the F12 locus in our cohort and delineated the clinical, laboratory and genetic features. Four families carried the p.Thr309Lys mutation in F12 gene. Haplotyping confirmed the hypothesis of a common founder. Six families were affected by U-HAE and 13 patients by sporadic InH-AAE. C4 levels were significantly lower in FXII-HAE than in InH-AAE. In the FXII-HAE group, none had attacks exclusively in high estrogenic states; acute attacks were treated with icatibant. Prophylaxis with tranexamic acid reduced the attack frequency in most patients. Our study provides new data on the diagnosis, clinical features and treatment of non-histaminergic angioedema, underlying the role of the screening for F12 mutations.