The Levels of the Lectin Pathway Serine Protease MASP-1 and Its Complex Formation with C1 Inhibitor Are Linked to the Severity of Hereditary Angioedema.

C1 inhibitor (C1-INH) is known to form complexes with the lectin complement pathway serine proteases MASP-1 and MASP-2. Deficiency of C1-INH is associated with hereditary angioedema (HAE), an autosomal inherited disease characterized by swelling attacks caused by elevated levels of bradykinin. MASP-1 was shown to cleave high m.w. kininogen into bradykinin; therefore, we hypothesized that MASP-1 levels and the quantity of MASP-1/C1-INH complexes might be associated with different paraclinical and clinical outcomes of HAE. We measured MASP-1 serum concentrations and endogenous MASP-1/C1-INH complex levels in 128 HAE patients and 100 controls. Relatively high levels of pre-existing MASP-1/C1-INH complexes were observed in normal serum, and we found that both the serum levels of MASP-1 and the complex formation between MASP-1 and C1-INH were significantly reduced in HAE patients compared with matched controls (p < 0.0001). The level of MASP-1 and MASP-1/C1-INH complexes in HE patients correlated with the level of C1-INH (p = 0.0009 and p = 0.0047, respectively), the level of C4 (p = 0.0084 and p < 0.0001, respectively), and the number of attacks in the year of blood sampling (p = 0.0075 and p = 0.0058, respectively). In conclusion, we show that MASP-1/C1-INH complexes circulate in normal human blood. The levels of MASP-1 and MASP-1/C1-INH complexes are reduced in HAE patients compared with controls. Both MASP-1 and MASP-1/C1-INH complexes are related to the degree of complement C4 consumption, as well as the severity of disease. These results suggest that MASP-1 may exert a previously unrecognized role in the pathophysiology of HAE.

Coagulation Factor XII Gene Mutation in Brazilian Families with Hereditary Angioedema with Normal C1 Inhibitor.

BACKGROUND: Hereditary angioedema (HAE) with normal C1 inhibitor (C1-INH) is a rare disorder. Mutations of the gene encoding coagulation factor XII have been identified in a subset of patients with this condition. Our aim was to investigate mutations in the F12 gene in patients with HAE with normal C1-INH from Brazil. METHODS: We studied 5 Brazilian families with index female patients who presented with recurrent angioedema with normal C1-INH and C4 levels. Genomic DNA was isolated from whole blood and PCR was performed. Mutations were detected by the sequencing of exon 9 of the F12 gene and allelic discrimination. RESULTS: The c.983C>A (p.Thr328Lys) mutation was identified in 16 subjects, from 4 of the 5 families studied, including 8 patients with symptoms of HAE with normal C1-INH (87.5% women) and 8 subjects asymptomatic for HAE (25% women). Mean age at onset of symptoms among the FXII-HAE patients was 13.8 years (range 6-25 years). Recurrent abdominal pain (100%) and subcutaneous angioedema (87.5%) were the most frequent clinical presentations. Two patients presented with associated laryngeal edema. In keeping with previous observations in patients with both C1-INH-HAE and HAE with normal C1-INH, all 7 women with FXII-HAE reported triggering or worsening of symptoms upon intake of estrogen-containing oral contraceptives and/or pregnancy. CONCLUSIONS: We report for the first time in Brazil a mutation in the F12 gene as a likely cause of HAE with normal C1-INH in patients with recurrent attacks of angioedema and/or abdominal pain. A higher frequency of abdominal pain attacks and onset of symptoms at a younger age were observed among Brazilian patients when compared to those from other parts of the world.

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.

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.

Acquired angioedema--occurrence, clinical features and associated disorders in a Danish nationwide patient cohort.

BACKGROUND: The prevalence of acquired angioedema (AAE) is hitherto unknown and, to date, less than 200 patients have been reported worldwide. AAE is associated with lymphoproliferative conditions and autoantibodies against C1 inhibitor (C1INH). Rituximab (RTX) is increasingly used in the treatment of AAE patients. METHODS: A nationwide study of AAE patients was performed in Denmark. Clinical features, associated disorders, treatments and outcomes were registered. RESULTS: Eight AAE patients were identified. The diagnostic delay was on average 1 year and 8 months. Patients were treated with C1INH concentrate or icatibant on demand. Six patients were diagnosed with a clonal B-cell disorder during follow-up, on average 2.5 years after the first swelling. Two patients had monoclonal B-cell lymphocytosis (MBL). Two patients received RTX. CONCLUSIONS: AAE is a rare condition occurring in less than 10% of patients with C1INH deficiency in Denmark. AAE is highly associated with haematologic disorders, and we recommend yearly follow-up visits with clinical examination and blood tests including flow cytometry to diagnose B-cell conditions at an early stage. We report 2 patients with AAE and associated MBL, which is a benign expansion of clonal B lymphocytes. MBL can be the precursor of chronic lymphocytic leukaemia or is associated with non-Hodgkin's lymphoma. If angioedema is poorly controlled with standard treatment regimens, we suggest treatment of the associated haematologic disorder. Based on a review of the literature and our own data, we recommend therapy with RTX, especially in patients with anti-C1INH autoantibodies.

Angioedema: an overview and update.

Angioedema is an increasing cause of hospitalizations in the United States. This syndrome presents with non-pitting, asymmetric swelling of the face, lips, tongue, larynx, genitalia, and extremities, although any part of the body can be involved. Common causes of angioedema include allergic reactions and ACE inhibitors. Hereditary angioedema is a rare form of angioedema that can be diagnosed by screening with a C4 level. In 2009, three new treatments for hereditary angioedema were approved for use in the United States, revolutionizing management of this rare disease.

Anti-C1-Inhibitor Autoantibody Detection by ELISA.

Enzyme-linked immunosorbent assay (ELISA) is a quantitative analytical method used to measure the concentration of molecules in biological fluids through antigen-antibody reactions. Here we describe the measurement of anti-C1-inhibitor autoantibodies by an indirect ELISA. In this method patients' sera are incubated in a microplate coated with plasma derived C1-inhibitor.

Complement 1 inhibitor is a regulator of the alternative complement pathway.

We studied complement 1 inhibitor (C1-INH) as an inhibitor of the alternative complement pathway. C1-INH prevented lysis, induced by the alternative complement pathway, of paroxysmal nocturnal hemoglobinuria (PNH) erythrocytes in human serum. It inhibited the binding of both factors B and C3 to PNH and rabbit erythrocytes and blocked the ability of factor B to restore alternative-pathway function in factor B-depleted serum. C1-INH did not bind to factors B or D but did bind to immobilized C3b and cobra venom factor (CVF), a C3b analogue. C1-INH prevented factor B from binding to CVF-coated beads and dissociated bound factor B from such beads. Factor B and C1-INH showed cross competition in binding to CVF-coated beads. Factor D cleaved factor B into Bb and Ba in the presence of C3b. Cleavage was markedly inhibited when C3b was preincubated with C1-INH. C1-INH inhibited the formation of CVFBb and decreased the C3 cleavage. Removal of C1-INH from serum, in the presence of Mg-EGTA with an anti-C1-INH immunoabsorbant, markedly increased alternative-pathway lysis. C1-INH interacts with C3b to inhibit binding of factor B to C3b. At physiologic concentrations, it is a downregulator of the alternative pathway convertase.

Acquired angioedema: Autoantibody associations and C1q utility as a diagnostic tool.

Acquired Angioedema (AAE) is a rare condition classified into two subtypes: Type I, which is associated with lymphoproliferative disorders, and Type II, which is linked with autoantibodies against C1-esterase inhibitor (C1-INH). Unlike Type I AAE, Type II has no correlation with lymphoproliferative disorders. We report the evaluation of angioedema that was associated with an underlying lymphoproliferative disorder for the purpose of discussing the relationship between C1q and a diagnosis of AAE. A literature review was completed for the purpose of assessing the diagnostic value of C1q when used in the workup of AAE. A PubMed/Web of Science search (1976-2010) produced 78 references (yielding 167 individual cases of AAE) using terminology "AAE." The case described a patient with a depressed C1q (<3.5 mg/dL), decreased C4 (<3 mg/dL), decreased C1-inhibitor (1 mg/dL), decreased functional C1-INH (12%), and decreased total complement (<10 U/mL). Autoantibodies against C1-INH (free and bound respectively) were normal (12.4% and 10.1% of the standard of deviation). Using the above figures and data collected from the literature search, we tabulated 168 individual cases of AAE. Of the 168 cases, C1q was drawn in 104 cases, and 64 cases have no information regarding C1q. There are 10 cases where the C1q was documented as normal. With these values, a correlation between C1q and a diagnosis of AAE was assessed: A decreased C1q correlated with a diagnosis of AAE approximately 56%-94% of the time. C1q is a useful tool when working up a case of AAE.

Variability of prodromal signs and symptoms associated with hereditary angioedema attacks: a literature review.

Hereditary angioedema (HAE) is a rare disease caused by deficiency in the production or function of C1 inhibitor. It predisposes individuals to paroxysmal acute attacks causing painful, debilitating, disfiguring, and life-threatening angioedema. Prodromes occurring hours to days before attacks have been described in the literature; however, their significance as predictive signals of impending attacks is uncertain. Given the morbidity and mortality associated with HAE attacks and the increasing availability of therapeutic products for their treatment, identifying prodromes that accurately predict the onset of attacks could provide the basis for the development of a validated instrument to identify the onset of such attacks requiring abortive therapeutic intervention before the development of clinically significant angioedema. The aim of this study was to review the literature to identify the prodromes reported to occur with HAE attacks. A literature review of English language journal articles was performed using search terms hereditary angioedema, HAE, angioneurotic edema, prodrome, signs, and symptoms. Nineteen original English language articles that included both case reports and studies describing prodromes associated with HAE attacks were obtained. Our review indicates that there is significant variability in the expression, manifestation, prevalence, timing, and predictive reliability of the prodromes that have been described. There is considerable variability of the prodromal manifestations that may occur before or during HAE attacks. We have not found any evidence that their sensitivity and specificity for accurately predicting such attacks has been studied.

Pathogenesis and laboratory diagnosis of hereditary angioedema.

Hereditary angioedema (HAE) was first described in the 19th century. Over the past 50 years, many details of the pathophysiology and molecular biology of HAE have been elucidated. Two types of HAE, type I and type II, result from mutations in the gene for the broad-spectrum protease inhibitor C1 inhibitor (C1INH). Type I HAE is characterized by low antigenic and functional C1INH levels and type II HAE has normal antigenic but low functional C1INH levels. Type III HAE, by contrast, has normal antigenic and functional C1INH levels. In some families, type III HAE has been linked to mutations in Hageman factor. C1INH is the primary inhibitor of the complement proteases C1r and C1s as well as the contact system proteases activated Hageman factor (coagulation factor XIIa and XIIf) and plasma kallikrein. It is also an inhibitor of plasmin and coagulation factor XIa. The primary mediator of swelling in HAE has now been unequivocally shown to be bradykinin, generated from activation of the plasma contact system. The knowledge gained concerning the underlying mechanisms of the different types of HAE allow the clinician to approach the laboratory diagnosis with confidence and provides opportunities for novel therapeutic strategies.

Melkersson-Rosenthal syndrome and acquired C1 inhibitor deficiency.

BACKGROUND: Melkersson-Rosenthal syndrome (MRS) is a rare disease whose full-blown form is characterized by orofacial swelling, facial palsy and lingua plicata. OBJECTIVE: To investigate the complement system as well as its role in patients with MRS. METHODS: Seven patients presenting at this hospital between November 2002 and May 2003 and meeting the diagnostic criteria according to Hornstein were evaluated retrospectively. The investigations included clinical signs, an analysis of the complement system including levels of CH50, C3, C4, C1 inhibitor (INH) functions and C1-INH antigen detection. RESULTS: Two female patients showed isolated low levels of functional C1-INH as determined by duplicate tests. Both patients took estrogen-progestin contraceptives. CONCLUSION: Since deficiency in plasma protease C1-INH is known to lead to recurrent angioedema, we hypothesize that low levels of functional C1-INH may have contributed to the orofacial swelling in the 2 patients.

Acquired angioedema associated with hereditary angioedema due to C1 inhibitor deficiency.

Angioedema caused by C1 inhibitor deficiency is a rare disorder that may be either hereditary or acquired, the latter being mainly associated with lymphoproliferative disorders. A 51-year-old woman who had suffered from episodes of acute peripheral edema since she was 12 was diagnosed with hereditary angioedema at the age of 40 and remained stable with stanozolol. Due to a worsening of her symptoms she was reassessed and low levels of C1q and an abnormal lymphocyte count were detected. Immunophenotyping of peripheral blood revealed 9% monoclonal lambda B cells with a follicular center phenotype. The histopathology was consistent with a grade II follicular lymphoma stage IV-A.With chemotherapy, the hematologic disease was controlled and C1q levels returned to normal values. This represents a rare case of a patient with hereditary angioedema who developed acquired angioedema due to a lymphoma that was associated with a reduction in the levels of C1q as her symptoms worsened.

Recombinant human C1-inhibitor inhibits cytotoxicity induced by allo- and xenoantibodies.

Antibody-mediated rejection (AMR) is usually poorly controlled, especially in the context of pretransplant immunization, and remains an unsolved issue in xenotransplantation. In order to study prevention and/or treatment of AMR through an early blockade of the complement classical pathway, we designed two strategies to test the effect of a new recombinant human C1-inhibitor that inhibits C1 esterase (rhC1-INH; Pharming, The Netherlands), in a complement-dependent cytotoxicity assay, in the contexts of pretransplant anti-donor alloimmunization and pig-to-primate combinations in order to compare the situations. RhC1-INH appeared to be efficient, in allo- and xenotransplantation settings to block cytotoxicity when given at the initiation of (preventive strategy) or during (curative strategy) the cytotoxicity assay. Importantly, we showed that a small amount of exogenous rhC1-INH was sufficient to prevent cytotoxicity induced by anti-donor alloantibody, thus possibly helping to prevent or treat AMR in preimmunized patients. These in vitro data lead to future in vivo studies in models of AMR in pigs and baboons in allotransplantation and xenotransplantation, in which cytotoxicity due to Gal and non-Gal antibodies is so detrimental.

Interaction of Neisseria gonorrhoeae with classical complement components, C1-inhibitor, and a monoclonal antibody directed against the Neisserial H.8 antigen.

Strains of Neisseria gonorrhoeae were used to evaluate bactericidal and opsonic properties of McAb 10 directed against the Neisserial outer membrane antigen, H.8. Gonococci were either serum resistant in the absence but serum sensitive in the presence, of McAb 10, or serum sensitive or serum resistant regardless of the presence of McAb 10. Strain JS3, which fell in the former category, was used in subsequent studies. C1 zymogen formed by reassociation of isolated C1 subunits was not directly activated by JS3 in the presence or absence of C1-inhibitor. JS3 thus was unable to directly activate the classical pathway independently of antibody. When purified classical pathway components were used to deposit C3 on JS3 in the absence of serum regulatory proteins or antibodies, added C1-inhibitor reduced C3 binding to background levels. When McAb 10 was present, C3 binding was unaffected by C1-inhibitor. Covalently bound, large molecular weight C3 alpha-chain-gonococcal complexes were disbanded by methylamine release of ester linkages. Released 125I-C3 migrated as C3b without degradation by gonococcal proteases. Purified classical components alone or McAb 10 alone facilitated JS3 killing by neutrophils; when combined, the two provided maximal killing. Levels of McAb 10 that only slightly increase C3 deposition on JS3 are bactericidal in serum and maximally opsonic in combination with purified classical pathway components.