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

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

An ABC of the Warning Signs of Hereditary Angioedema.

Hereditary angioedema (HAE) with C1 inhibitor deficiency is a genetic disorder that clinically manifests with attacks of angioedema in the subcutaneous and submucosal tissues, mainly in the extremities, abdomen, and upper airway. During attacks, vascular permeability is increased due to increased bradykinin (BK). This means that special therapies are needed for attacks that do not respond to traditional antiallergic therapies involving antihistamines, corticosteroids, and epinephrine. The recurring attacks may disable patients and lead to frequent visits to emergency rooms where misdiagnoses are common. HAE attacks may be fatal when upper-airway edema occurs, if proper treatment with a C1 inhibitor concentrate or BK receptor antagonist is not administered or an emergency tracheostomy is not performed. We propose a mnemonic method for the warning signs of HAE for the use as a diagnostic tool, i.e., the so-called "ABC" of the warning signs of HAE. The letters represent the following: A = Angioedema, B = Bradykinin, C = C1 inhibitor, D = Distress factors, E = Epinephrine nonresponsive, F = Family history, and G = Glottis/Gastrointestinal edema. To avoid fatalities, medical staff and patients, including family members, must be aware of HAE. An alphabetical mnemonic method has been developed and we hope it may benefit patients.

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 Sibenik, 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.

'Epinephrine-resistant' angioedema.

A man in his 60s was brought to the emergency department, with airway compromise and dysarthria due to a grossly enlarged tongue. As he was on a current course of antibiotics, he was treated for a likely antibiotic-associated allergic reaction. However, as he failed to improve with intramuscular and nebulised epinephrine, another cause of his symptoms was sought. Further discussion revealed a history of chronic lymphocytic leukaemia (CLL), which had recently relapsed. Investigations were ordered to confirm that the symptoms were due to acquired angioedema, and the patient was managed for this diagnosis based on the presence of an undetectable C4 level. This diagnosis was later confirmed when the results of specialist tests became available. The patient was treated for his relapsed CLL with good effect, and has had no further episodes of angioedema and an improvement in the level of his C1 esterase protein level and function.

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.

[Acquired angioedema with C1-INH deficiency and accompanying chronic spontaneous urticaria in a patient with chronic lymphatic B cell leukemia]. / Erworbenes Angioödem mit C1-INH-Defizienz und begleitender chronisch spontaner Urtikaria bei chronisch lymphatischer B-Zell-Leukämie.

Acquired angioedema due to C1 inhibitor deficiency (C1-INH-AAE) is characterized by recurrent edema of the subcutaneous and/or submucosal tissue without wheals and negative family history of angioedema. Here, we present the case of a patient with a chronic lymphatic B cell leukemia who suffered from both C1-INH-AAE and chronic spontaneous urticaria. Oral corticosteroids, antihistamines, and the anti-IgE antibody omalizumab were applied to treat the chronic urticaria in combination with the plasma-derived C1 esterase inhibitor concentrate Berinert® and the bradykinin B2 receptor antagonist icatibant, but the symptoms did not improved significantly. Thus, polychemotherapy targeting the slow-growing lymphoproliferative disease including rituximab was initiated, which resulted in remission of both the urticaria and the angioedema.

Elevated D-dimers in attacks of hereditary angioedema are not associated with increased thrombotic risk.

BACKGROUND: Recommended management of attacks of hereditary angioedema (HAE) due to C1 esterase inhibitor (C1-INH) deficiency (C1-INH-HAE) includes therapy with exogenous C1INH. Thrombotic/thromboembolic events (TEE) have been reported with plasma-derived C1INH, but so far none with recombinant human C1INH (rhC1INH). This phase III, randomized, placebo (saline)-controlled study evaluated the safety of rhC1INH 50 IU/kg for the treatment of acute attacks in 74 patients with C1-INH-HAE. METHODS: Monitoring for TEE and assessment of risk of deep vein thrombosis (DVT) by the Wells prediction rule were performed, and levels of fibrin degradation products (plasma D-dimers) were assessed before study drug administration (baseline), 2 h, and 7 days posttreatment. RESULTS: Plasma D-dimer levels were elevated in 80% of the patients (median [25th-75th percentiles]: 2149 [480-5105] µg/l; normal ≤250 µg/l) and were higher in patients with submucosal (abdominal, oropharyngeal-laryngeal) attacks (3095 [890-10000] µg/l; n = 29) compared with subcutaneous (peripheral, facial) attacks (960 [450-4060] µg/l; n = 35). Median plasma D-dimer levels were comparable across treatment groups at baseline (1874 [475-4568] µg/l rhC1INH; 2259 [586-7533] µg/l saline) and 2 h postinfusion (2389 [760-4974] µg/l rhC1INH; 2550 [310-8410] µg/l saline); median plasma D-dimer levels were decreased by Day 7 in both groups (425 [232-3240] µg/l rhC1INH; 418 [246-2318] µg/l saline). No increased risk of DVT was identified, nor any TEE reported in rhC1INH treated or controls. CONCLUSION: Elevated plasma D-dimer levels were associated with acute C1-INH-HAE attacks, particularly with submucosal involvement. However, rhC1INH therapy was not associated with thrombotic events.

A novel splice site mutation in the SERPING1 gene leads to haploinsufficiency by complete degradation of the mutant allele mRNA in a case of familial hereditary angioedema.

Hereditary angioedema due to C1-inhibitor deficiency (HAE-C1INH) is a rare autosomal-dominant and life-threatening disorder caused by mutations in SERPING1 gene. It is characterized by attacks of angioedema involving the skin and/or the mucosa of the upper airways, as well as the intestinal mucosa. Here we report the case of a patient with HAE-C1INH without family history of angioedema. By sequencing the SERPING1 gene we detected a novel mutation (c.1249 + 5G > A) affecting the 5' donor splice site in intron 7. We analyzed the SERPING1 cDNA expecting a defect in splicing process but only the wild type allele was detected. SNP analysis of the cDNA sequence demonstrated that only one of the two alleles was present, indicating that the mRNA from the mutated allele was completely degraded. This study reinforces the concept of incomplete penetrance of this disorder since the patients' mother never presented any sign of angioedema despite carrying the same mutation.

[Recurrent isolated angioedema as a result of acquired C1 inhibitor deficiency]. / Geïsoleerd angio-oedeem door verworven C1-esteraseremmerdeficiëntie.

Isolated angioedema may be the presenting symptom of acquired C1 inhibitor (C1-INH) deficiency. C1-INH deficiency is associated with lymphoproliferative disorders. Treatment of the underlying disease can result in a complete reversal of clinical and complement abnormalities. We describe a 41-year-old woman who was referred to our emergency department with recurrent episodes of isolated angioedema. Initially, her angioedema was linked to the use of angiotensin receptor blockers. However, after discontinuation of this drug angioedema recurred. Additional investigations revealed the presence of acquired C1-INH deficiency caused by an indolent non-Hodgkin's lymphoma. Treatment with rituximab resulted in complete clinical and biochemical remission of the acquired angioedema.

Recombinant human C1-esterase inhibitor relieves symptoms of hereditary angioedema attacks: phase 3, randomized, placebo-controlled trial.

BACKGROUND: Hereditary angioedema (HAE), caused by C1 inhibitor (C1INH) deficiency or dysfunction, is characterized by recurrent attacks of tissue swelling affecting multiple anatomic locations. Recombinant human C1INH (rhC1INH) has been shown effective for acute treatment of HAE attacks. OBJECTIVE: To evaluate the efficacy and safety of rhC1INH (50 IU/kg to maximum 4,200 IU/treatment) vs placebo in a larger HAE population. METHODS: Seventy-five patients experiencing peripheral, abdominal, facial, and/or oropharyngeal laryngeal attacks were randomized (3:2) to rhC1INH (n = 44) or placebo (saline; n = 31). Efficacy was assessed by patient responses on a Treatment Effect Questionnaire (TEQ) and visual analog scale (VAS). Safety also was evaluated. RESULTS: Median (95% confidence interval) time to beginning of symptom relief at the primary attack location was 90 minutes (61-150) in rhC1INH-treated patients vs 152 minutes (93, not estimable) in placebo-treated patients (P = .031) based on the TEQ and 75 minutes (60-105) vs 303 minutes (81-720, P = .003) based on a VAS decrease of at least 20 mm. Median time to minimal symptoms was 303 minutes (240-720) in rhC1INH-treated patients vs 483 minutes (300-1,440) in placebo-treated patients based on the TEQ (P = .078) and 240 minutes (177-270) vs 362 minutes (240, not estimable; P = .005), based on an overall VAS less than 20 mm. Overall, rhC1INH was safe and well tolerated; no thromboembolic events, anaphylaxis, or neutralizing antibodies were observed. CONCLUSION: Relief of symptoms of HAE attacks was achieved faster with rhC1INH compared with placebo as assessed by the TEQ and VAS, with a positive safety profile. Results are consistent with previous studies showing efficacy and safety of rhC1INH in patients with HAE.

The burden of illness in patients with hereditary angioedema.

OBJECTIVE: Hereditary angioedema (HAE) is a rare genetic disease characterized by long-term recurrent attacks of subcutaneous or submucosal edema in different parts of the body. A comprehensive review of the literature on burden of illness for patients with HAE is presented. DATA SOURCES: A Boolean search was performed using MEDLINE and EMBASE databases and the Internet. STUDY SELECTION: Articles discussing aspects of the burden of illness in HAE were selected. Topics focused on the course of the disease, nature of attacks, treatment, quality of life, and costs. RESULTS: Hereditary angioedema is associated with a significant and multifaceted disease burden. Diagnosis is often delayed for years, with patients receiving ineffective treatment and unnecessary medical procedures before diagnosis. HAE attacks are painful, unpredictable, and debilitating and often require emergency medical attention. Attacks can affect a patient's daily activities, including work or schooling. Depression and anxiety are prevalent in patients with HAE. Recent advances in treatment provide patients with effective and well-tolerated prophylactic and on-demand therapeutic options. However, end points specific to HAE that better measure the impact of treatment on disease burden are lacking. Furthermore, there is a notable paucity of literature directed toward physicians who are instrumental in diagnosing and treating patients with HAE (eg, emergency department). CONCLUSION: More publications are broadening the understanding of HAE. However, important gaps remain. Effective management of HAE requires a more comprehensive understanding of the disease burden so that disease management can be individualized to meet specific patient needs.

[Recurrent abdominal pain and ascites in patients suffering from congenital angioedema due to C1 inhibitor deficiency. Retrospective analysis]. / Nawracajace bóle brzucha i wodobrzusze u pacjentów z wrodzonym obrzekiem naczynioruchowym na tle niedoboru C1 inhibitora. Analiza retrospektywna.

The aim of the study was the estimation of diagnostic value abdominal ultrasonography in recurrent attacks the patients suffering from hereditary angioedema. The retrospective analysis was done in 150 patients with C1 inhibitor deficiency and abdomen attack of angioedema connected with this. In 55 patients severe 2-3 days longlasting abdomen attacks with nausea, diarrhoea and weakening were the first symptoms of the illness and causing particular diagnostic problem. In 95 remaining patients abdomen attack appeared in the course of illness manifesting external angioedema of hands, feets, face, genitalia or larynx. The frequency of abdominal attacks was different from 1-15/year. Diagnostic problem was the reason of laparotomy in 19.3% of patients which did not explain the reason of symptoms. Only in 23 % of patients US of abdomen was done, which revealed the presence of ascites, which disappeared together with abdomen symptoms. US often allowed to show the place of regional angioedema usually in the most cases in intestine wall.

Overview of hereditary angioedema caused by C1-inhibitor deficiency: assessment and clinical management.

Hereditary angioedema due to C1-inhibitor deficiency (HAE-C1-INH) is a rare, autosomal-dominant disease. HAE-C1-INH is characterized by recurrent attacks of marked, diffuse, nonpitting and nonpruritic skin swellings, painful abdominal attacks, and laryngeal edema. The extremities and the gastrointestinal tract are most commonly affected. Swelling of the upper respiratory mucosa poses the greatest risk because death from asphyxiation can result from laryngealedema. HAE-C1-INH attacks are variable, unpredictable, and may be induced by a variety of stimuli, including stress or physical trauma. Because the clinical presentation of HAE-C1-INH is similar to other types of angioedema, the condition may be a challenge to diagnose. Accurate identification of HAE-C1-INH is critical in order to avoid asphyxiation by laryngeal edema and to improve the burden of disease. Based on an understanding of the underlying pathophysiology of IHAE-C1-INH, drugs targeted specifically to the disease, such as C1-inhibitor therapy, bradykinin B2-receptor antagonists, and kallikrein-inhibitors, have become available for both treatment and prevention of angioedema attacks. This article reviews the clinical features, differential diagnosis, and current approaches to management of HAE-C1-INH.

In pursuit of excellence: an integrated care pathway for C1 inhibitor deficiency.

There are estimated to be approximately 1500 people in the United Kingdom with C1 inhibitor (C1INH) deficiency. At BartsHealth National Health Service (NHS) Trust we manage 133 patients with this condition and we believe that this represents one of the largest cohorts in the United Kingdom. C1INH deficiency may be hereditary or acquired. It is characterized by unpredictable episodic swellings, which may affect any part of the body, but are potentially fatal if they involve the larynx and cause significant morbidity if they involve the viscera. The last few years have seen a revolution in the treatment options that are available for C1 inhibitor deficiency. However, this occurs at a time when there are increased spending restraints in the NHS and the commissioning structure is being overhauled. Integrated care pathways (ICP) are a tool for disseminating best practice, for facilitating clinical audit, enabling multi-disciplinary working and for reducing health-care costs. Here we present an ICP for managing C1 inhibitor deficiency.

Hereditary angioedema nationwide study in Slovenia reveals four novel mutations in SERPING1 gene.

Hereditary angioedema (HAE) is a rare autosomal dominant disease characterized by swelling of the face, lips, tongue, larynx, genitalia, or extremities, with abdominal pain caused by intra-abdominal edema. HAE is caused by mutations affecting the C1 inhibitor gene, SERPING1, resulting in low levels of C1 inhibitor (Type I HAE) or normal levels of ineffective C1 inhibitor (Type II HAE). A nationwide survey identified nine unrelated families with HAE in Slovenia, among whom 17 individuals from eight families were recruited for genetic analyses. A diagnosis of HAE was established in the presence of clinical and laboratory criteria (low C1 inhibitor antigenic levels and/or function), followed up by a positive family history. Genetic studies were carried out using PCR and sequencing to detect SERPING1 mutations in promoter, noncoding exon 1, the 7 coding exons, and exon-intron boundaries. Multiplex ligation-dependent probe amplification was performed in order to search for large deletions/duplications in SERPING1 gene. A mutation responsible for HAE was identified in patients from seven families with the disease. In HAE type I families, one previously reported substitution (Gln67Stop, c.265C>T) and four novel mutations were identified. The new mutations included two missense substitutions, Ser128Phe (c.449C>T), and Glu429Lys (c.1351G>A), together with two frameshift mutations, indel (c.49delGinsTT) and deletion (c.593_594delCT). Both families with HAE type II harbored the two well-known substitutions affecting the arginyl residue at the reactive center in exon 8, Arg444Cys (c.1396C>T) and Arg444His (c.1397G>A), respectively. In one patient only the homozygous variant g.566T>C (c.-21T>C) was identified. Our study identified four novel mutations in the Slovenian HAE population, highlighting the heterogeneity of mutations in the SERPING1 gene causing C1 inhibitor deficiency and HAE. In a single patient with HAE a homozygous variant g.566T>C (c.-21T>C) might be responsible for the disease.