Article

Baseline level of functional C1-inhibitor correlates with disease severity scores in hereditary angioedema.

Department of Internal Medicine, Semmelweis University, Budapest, Hungary.
Clinical Immunology (impact factor: 4.05). 11/2009; 134(3):354-8. DOI:10.1016/j.clim.2009.11.002 pp.354-8
Source: PubMed

ABSTRACT The diagnosis of hereditary angioedema (HAE) is based on complement tests. We studied for the first time the possible association between complement parameters measured at the time of diagnosis and disease severity in 115 patients with HAE. Serum levels of functional C1-inhibitor (C1-INH(f)), antigenic C1-inhibitor (C1-INH(a)), C4 and hemolytic activity of the classical pathway (CH50) were determined at the time of diagnosis. We found a significant correlation between severity scores and baseline C1-INH(f) levels, as determined by ELISA assay (p=0.0003). On the other hand, there was no correlation between severity scores and other complement parameters (C1-INH(a), C4, and CH50). We consider the correlation between severity scores and baseline C1-INH(f) levels an important pathophysiological observation. Our findings underlie the potential significance of monitoring functional C1-INH levels in relation to clinical disease course.

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    Article: Mutational spectrum and phenotypes in Danish families with hereditary angioedema because of C1 inhibitor deficiency.
    A Bygum, C R Fagerberg, D Ponard, N Monnier, J Lunardi, C Drouet
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    ABSTRACT: Hereditary angioedema (HAE), type I and II, is an autosomal dominant disease with deficiency of functional C1 inhibitor protein causing episodic swellings of skin, mucosa and viscera. HAE is a genetically heterogeneous disease with more than 200 different mutations in the SERPING1 gene. A genotype-phenotype relationship does not seem to exist in HAE, although the polymorphism c.-21T>C of exon 2 has been reported to be associated with a more severe phenotype. We aimed to establish the mutational spectrum of C1 inhibitor deficiency in Denmark and investigate the possible disease-aggravating effect of the c.-21T>C polymorphism. Hereditary angioedema was diagnosed based on clinical features and C1 inhibitor deficiency. A general severity score ranging from 0 to 10 was developed based on age at disease onset, clinical manifestations and treatment experiences. SERPING1 gene investigation was performed by exon sequencing followed by multiplex ligation-dependent probe amplification genomic rearrangement analysis in all known Danish HAE families. Fifty-nine patients with HAE from 26 families were included in this study. The mean disease severity score was 7.12 [1-10], and the mean C1 inhibitor function was 26% [20-46%]. The sensitivity of the mutational screening was 96%, and 13 new mutations were found in this Danish patient cohort. Nine patients (15%) carried the c.-21T>C polymorphism, but they didn't have a more severe phenotype. Thirteen new mutations were identified in the Danish HAE population. No correlation between the c.-21T>C polymorphism, the biochemical values of C1 inhibitor function and the clinical severity score was found.
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    Article: A single nucleotide deletion at the C1 inhibitor gene as the cause of hereditary angioedema: insights from a Brazilian family.
    M F Ferraro, A S Moreno, E C Castelli, E A Donadi, M S Palma, H A Arcuri, A P Lange, K Bork, W Sarti, L K Arruda
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    ABSTRACT: Hereditary angioedema is an autosomal dominant disease characterized by episodes of subcutaneous and submucosal edema. It is caused by deficiency of the C1 inhibitor protein, leading to elevated levels of bradykinin. More than 200 mutations in C1 inhibitor gene have been reported. The aim of this study was to analyze clinical features of a large family with an index case of hereditary angioedema and to determine the disease-causing mutation in this family. Family pedigree was constructed with 275 individuals distributed in five generations. One hundred and sixty-five subjects were interviewed and investigated for mutation at the C1 inhibitor gene. Subjects reporting a history of recurrent episodes of angioedema and/or abdominal pain attacks underwent evaluation for hereditary angioedema. We have identified a novel mutation at the C1 inhibitor gene, c.351delC, which is a single-nucleotide deletion of a cytosine on exon 3, resulting in frameshift with premature stop codon. Sequencing analysis of the hypothetical truncated C1 inhibitor protein allowed us to conclude that, if transcription occurs, this protein has no biological activity. Twenty-eight members of the family fulfilled diagnostic criteria for hereditary angioedema and all of them presented the c.351delC mutation. Variation in clinical presentation and severity of disease was observed among these patients. One hundred and thirty-seven subjects without hereditary angioedema did not have the c.351delC mutation. The present study provides definitive evidence to link a novel genetic mutation to the development of hereditary angioedema in patients from a Brazilian family.
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    Article: Cleavage of kininogen and subsequent bradykinin release by the complement component: mannose-binding lectin-associated serine protease (MASP)-1.
    József Dobó, Balázs Major, Katalin A Kékesi, István Szabó, Márton Megyeri, Krishnan Hajela, Gábor Juhász, Péter Závodszky, Péter Gál
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    ABSTRACT: Bradykinin (BK), generated from high-molecular-weight kininogen (HK) is the major mediator of swelling attacks in hereditary angioedema (HAE), a disease associated with C1-inhibitor deficiency. Plasma kallikrein, activated by factor XIIa, is responsible for most of HK cleavage. However other proteases, which activate during episodes of angioedema, might also contribute to BK production. The lectin pathway of the complement system activates after infection and oxidative stress on endothelial cells generating active serine proteases: MASP-1 and MASP-2. Our aim was to study whether activated MASPs are able to digest HK to release BK. Initially we were trying to find potential new substrates of MASP-1 in human plasma by differential gel electrophoresis, and we identified kininogen cleavage products by this proteomic approach. As a control, MASP-2 was included in the study in addition to MASP-1 and kallikrein. The proteolytic cleavage of HK by MASPs was followed by SDS-PAGE, and BK release was detected by HPLC. We showed that MASP-1 was able to cleave HK resulting in BK production. MASP-2 could also cleave HK but could not release BK. The cleavage pattern of MASPs is similar but not strictly identical to that of kallikrein. The catalytic efficiency of HK cleavage by a recombinant version of MASP-1 and MASP-2 was about 4.0×10(2) and 2.7×10(2) M(-1) s(-1), respectively. C1-inhibitor, the major inhibitor of factor XIIa and kallikrein, also prevented the cleavage of HK by MASPs. In all, a new factor XII- and kallikrein-independent mechanism of bradykinin production by MASP-1 was demonstrated, which may contribute to the pro-inflammatory effect of the lectin pathway of complement and to the elevated bradykinin levels in HAE patients.
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Keywords

antigenic C1-inhibitor
 
baseline C1-INH(f)
 
clinical disease course
 
disease severity
 
ELISA assay
 
functional C1-inhibitor
 
hemolytic activity
 
monitoring functional C1-INH levels
 
pathophysiological observation
 
potential significance
 
Serum levels
 
severity scores
 
significant correlation