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R Schneppenheim

Publications and source records attributed to R Schneppenheim.

At least 19 recordsLinked to original sources
PubMed2006

Update on the pathophysiology and classification of von Willebrand disease: a report of the Subcommittee on von Willebrand Factor.

von Willebrand disease (VWD) is a bleeding disorder caused by inherited defects in the concentration, structure, or function of von Willebrand factor (VWF). VWD is classified into three primary categories. Type 1 includes partial quantitative deficiency, type 2 includes qualitative defects, and type 3 includes virtually complete deficiency of VWF. VWD type 2 is divided into four secondary categories. Type 2A includes variants with decreased platelet adhesion caused by selective deficiency of high-molecular-weight VWF multimers. Type 2B includes variants with increased affinity for platelet glycoprotein Ib. Type 2M includes variants with markedly defective platelet adhesion despite a relatively normal size distribution of VWF multimers. Type 2N includes variants with markedly decreased affinity for factor VIII. These six categories of VWD correlate with important clinical features and therapeutic requirements. Some VWF gene mutations, alone or in combination, have complex effects and give rise to mixed VWD phenotypes. Certain VWD types, especially type 1 and type 2A, encompass several pathophysiologic mechanisms that sometimes can be distinguished by appropriate laboratory studies. The clinical significance of this heterogeneity is under investigation, which may support further subdivision of VWD type 1 or type 2A in the future.

ADAM Proteins↗
PubMed2006

Linkage analysis in families diagnosed with type 1 von Willebrand disease in the European study, molecular and clinical markers for the diagnosis and management of type 1 VWD.

BACKGROUND: von Willebrand disease (VWD) type 1 is a congenital bleeding disorder caused by genetic defects in the von Willebrand factor (VWF) gene and characterized by a reduction of structurally normal VWF. The diagnosis of type 1 VWD is difficult because of clinical and laboratory variability. Furthermore, inconsistency of linkage between type 1 VWD and the VWF locus has been reported. OBJECTIVES: To estimate the proportion of type 1 VWD that is linked to the VWF gene. PATIENTS AND METHODS: Type 1 VWD families and healthy control individuals were recruited. An extensive questionnaire on bleeding symptoms was completed and phenotypic tests were performed. Linkage between VWF gene haplotypes and the diagnosis of type 1 VWD, the plasma levels of VWF and the severity of bleeding symptoms was analyzed. RESULTS: Segregation analysis in 143 families diagnosed with type 1 VWD fitted a model of autosomal dominant inheritance. Linkage analysis under heterogeneity resulted in a summed lod score of 23.2 with an estimated proportion of linkage of 0.70. After exclusion of families with abnormal multimer patterns the linkage proportion was 0.46. LOD scores and linkage proportions were higher in families with more severe phenotypes and with phenotypes suggestive of qualitative VWF defects. About 40% of the total variation of VWF antigen could be attributed to the VWF gene. CONCLUSIONS: We conclude that the diagnosis of type 1 VWD is linked to the VWF gene in about 70% of families, however after exclusion of qualitative defects this is about 50%.

Adolescent↗
PubMed2006

A quantitative analysis of bleeding symptoms in type 1 von Willebrand disease: results from a multicenter European study (MCMDM-1 VWD).

BACKGROUND: A quantitative description of bleeding symptoms in type 1 von Willebrand disease (VWD) has never been reported. OBJECTIVES: The aim was to quantitatively evaluate the severity of bleeding symptoms in type 1 VWD and its correlation with clinical and laboratory features. PATIENTS AND METHODS: Bleeding symptoms were retrospectively recorded in a European cohort of VWD type 1 families, and for each subject a quantitative bleeding score (BS) was obtained together with phenotypic tests. RESULTS: A total of 712 subjects belonging to 144 families and 195 controls were available for analysis. The BS was higher in index cases than in affected family members (BS 9 vs. 5, P < 0.0001) and in unaffected family members than in controls (BS 0 vs. -1, P < 0.0001). There was no effect of ABO blood group. BS showed a strong significant inverse relation with either von Willebrand ristocetin cofactor (VWF:RCo), von Willebrand antigen (VWF:Ag) or factor VIII procoagulant activity (FVIII:C) measured at time of enrollment, even after adjustment for age, sex and blood group (P < 0.001 for all the four upper quintiles of BS vs. the first quintile, for either VWF:RCo, VWF:Ag or FVIII:C). Higher BS was related with increasing likelihood of VWD, and a mucocutaneous BS (computed from spontaneous, mucocutaneous symptoms) was strongly associated with bleeding after surgery or tooth extraction. CONCLUSIONS: Quantitative analysis of bleeding symptoms is potentially useful for a more accurate diagnosis of type 1 VWD and to develop guidelines for its optimal treatment.

ABO Blood-Group System↗
PubMed2005

Decreased plasma concentration of von Willebrand factor antigen (VWF:Ag) in patients with glycogen storage disease type Ia.

Despite highly increased blood lipids, patients with glycogen storage disease type Ia (GSD Ia) do not develop premature vascular complications. Since this could be due to changes of coagulation factors, coagulation tests (including von Willebrand factor (VWF) antigen (VWF:Ag) ELISA, VWF:collagen binding activity (VWF:CB) and VWF multimer analysis) were performed in 10 GSD Ia patients, single cases of other GSD types, and in both healthy and hyperlipidaemic controls. In 60% of GSD Ia patients we found abnormal results, with a decrease of VWF:Ag and multimer analysis showing reduced intensity of individual oligomers in the presence of all multimers with a normal triplet structure. We interpret these findings as an acquired 'von Willebrand syndrome type I' in GSD Ia. The underlying metabolic mechanism and a potential role in the protection from vascular complication still needs to be evaluated.

Adolescent↗
PubMed2005

Gene conversions are a common cause of von Willebrand disease.

von Willebrand disease (VWD), the most common inherited bleeding disorder, is very heterogeneous, both in its phenotype and genotype. One particular molecular mechanism of VWD is due to recombination events between the true gene and its pseudogene on chromosome 22. We assessed the frequency and extension of such events in 50 multi-ethnic index patients with severe VWD type 3 and in five index patients with VWD type 2M Vicenza. One additional unclassified patient had been diagnosed with possible VWD in Russia solely on a clinical basis. Gene conversions, previously thought to be rare events, were identified in >10% of our study population: in six multi-ethnic patients with severe VWD type 3, in one patient with VWD type 2M Vicenza and the Russian patient was finally diagnosed with VWD type 2B New York/Malmoe. Our results suggest a significant contribution of this particular molecular mechanism to the manifestation of VWD. The location of the gene conversions, their extension and their occurrence as homozygous, compound heterozygous or heterozygous mutations determines the resulting phenotype.

Cells, Cultured↗
PubMed2005

[Inborn and acquired von Willebrand disease].

Von Willebrand disease (VWD) is known for its marked heterogeneity which was already recognized by von Willebrand in 1926. The basis of phenotypic differentiation are quantitative and qualitative or functional differences between the different types and subtypes of VWD. Clinical relevant facts for the practitioner on diagnosis and therapy of von Willebrand disease and von Willebrand syndrome are presented.

Deamino Arginine Vasopressin↗
PubMed2004

[Classification of von Willebrand disease].

Von Willebrand disease (VWD) is known for its marked heterogeneity which was already recognized by von Willebrand in 1926. The basis of phenotypic differentiation are quantitative and qualitative or functional differences between the different types and subtypes of VWD. One of the most important tools in the classification of VWD is multimer analysis that visualizes many of the structural abnormalities of mutant VWF. The introduction of multimer analysis was followed by the identification of an increasing number of different VWD phenotypes that were first reviewed in 1987 by Ruggeri and Zimmerman, thus forming a first classification of the disease. However, the detection of additional phenotypes required a revision of the nomenclature at a time point when only a few types of VWD had already been analyzed on the molecular level. Consequently, the molecular data only played a minor role in the revised classification published by Sadler in 1994. The advent of molecular techniques provided the opportunity for genotype/phenotype studies which recently helped not only to elucidate or confirm important functions of VWF and its steps of post-translational processing but also many disease causing defects. The reproducible correlation between certain phenotypes and particular mutations can now be used for a molecular approach towards a soundly based classification of VWD, equally useful for the clinician and for research requirements.

Humans↗
PubMed2004

[Diagnostic standards of von Willebrand disease].

Von Willebrand disease (VWD) is caused by quantitative and/or qualitative defects of the von Willebrand factor (VWF), a multimeric high molecular glycoprotein. Typically, it affects the primary haemostatic system, which is reflected by a mucocutaneous bleeding tendency simulating a functional platelet defect. The VWF promotes its function in two ways: It promotes platelet adhesion to the injured vessel wall under conditions of high shear forces and it functions as carrier for factor VIII in plasma. Due to its complexity diagnosis of VWD is one of the most challenging of coagulation disorders. The stepwise diagnosis of VWD includes patient's and family history, orientating procedures (bleeding time, filter tests, platelet count, aPTT), confirmatory tests (VWF:Ag, VWF:RCo, VIII:C) and tests for final classification (VWF:CB, RIPA, multimeric analysis, bWF:FVIIIB, platelet VWF). Accumulating knowledge of the different clinical phenotypes and their pathophysiological basis was translated into a classification scheme that differentiated between quantitative and qualitative defects by means of quantitative and functional parameters and by analyzing the electrophoretic pattern of VWF multimers. The advent of molecular techniques provided the opportunity for genotype/phenotype studies which recently helped not only to elucidate or confirm important functions of VWF and the steps of its posttranslational processing but also many disease causing defects.

Diagnosis, Differential↗
PubMed2004

[Molecular genetics of von Willebrand disease].

Due to the multifunctional character of von Willebrand factor (VWF), its complex biosynthesis and structure, many different disease causing molecular mechanisms exist which explain the well known marked heterogeneity of clinical symptoms in von Willebrand disease (VWD). Identification of specific mutations that can either cause complete or partial absence of VWF, interfere with post-translation processing of VWF like dimerisation and multimerisation, impair intracellular transport or disturb particular functions of VWF, offered the opportunity for structure/function studies of VWF and genotype/phenotype analysis of VWD. Today the molecular tools for such studies are readily available, enabling us to identify the molecular defects in a reasonable time even in the case of the large and complex VWF gene with its 52 exons. Mutation analysis can help to find the correct diagnosis and to classify patients with VWD which may be crucial to choose the adequate therapy. It can also identify unaffected carriers of the disease gene among family members of patients with VWD. Furthermore, mutation analysis and the conclusions drawn from such data can further help to understand the molecular mechanisms of VWF not only in bleeding but also in arterial thrombotic disease.

Blotting, Southern↗
PubMed2004

[Diagnosis of thrombotic thrombocytopenic purpura].

As hallmark of TTP, generalized hyaline thrombi in the patient's microcirculation is known. These thrombi are composed of platelets and VWF. A severe defect of the VWF cleaving protease (VWF-CP) was found in all known patients with the inherited form of TTP. In contrary, although a severe deficiency of VWF-CP is specific for the acquired form, too, only a fraction of these patients is characterized by a severe deficiency. In most patients with a severe deficiency autoantibodies directed against VWF-CP is detectable in plasma. However, many patients with acquired TTP do not show any severe deficiency. Because treatment differs in inherited and acquired forms and as persistance of autoantibodies during clinical remission is of prognostic value, the determination of the activity of VWF-CP and of antibodies against VWF-CP are important parts in the workup of patients with TTP. In all methods for the determination of the activity of VWF-CP the first step is proteolysis of a specific substrate for the protease. In the second step the activity of the protease is measured by analysis of the residual VWF multimers, by the generation of specific fragments, by using the residual VWF:CB or VWF:RCo as marker of the loss of multimers or with help of specific monoclonal antibodies. In less than 30 min the cone and plate(let) aggregometer helps to distinguish between different forms of thrombotic microangiopathies. While adhesion and aggregation of platelets from a healthy person are clearly enhanced after addition of a small amount of plasma from a TTP patient, both characteristics are weakened by plasma from patients with other forms of thrombotic microangiopathy (dilution effect). Molecular genetics are established methods in the differentiation between inherited and acquired forms of TTP in those cases without autoantibodies against VWF-CP.

ADAM Proteins↗
PubMed2004

[Thrombotic thrombocytopenic purpura in childhood].

Thrombotic thrombocytopenic purpura (TTP) is a micro-angiopathic disease due to deficiency of the specific VWF cleaving protease (VWF-CP) ADAMTS13. The acquired form is caused by autoantibodies against VWF-CP, whereas mutations of the ADAMTS13 gene are responsible for inherited TTP. In childhood both forms exist with predominance of inherited TTP. The phenotype of TTP in childhood can be rather variable. Besides the classical clinical picture, abortive forms may occur that can delay the identification of patients at risk. The patients are frequently assumed to suffer from idiopathic thrombocytopenia (ITP) or Evans syndrome. Further efforts are necessary to accelerate correct diagnosis and to establish a risk-adapted prophylactic therapy.

ADAM Proteins↗
PubMed2003

[2% Haemophilia A patients without mutation in the FVIII gene].

In Germany, approximately 6,000 patients are suffering from haemophilia A. Screening methods cover 97% of the mutations. For the other patients the coding sequences of the FVIII gene have to be sequenced in total. Out of 1,350 patients, no mutation was observed in 80 patients. In 5 patients, we observed an inversion in intron 1. Known mutations were detected in 16 patients, and in 19 cases novel mutations were characterized (14 in coding regions and 5 in flanking introns). The mutations are mainly base pair substitutions, small deletions or insertions (max. 4 bp) and predicted to cause amino acid exchanges or frameshifts leading to premature stop codons. Moreover, 5 polymorphisms were identified in exons 14 and 26 as well as in introns 7 and 19. Further studies are necessary to identify their causative effects. Surprisingly, in 23 patients out of this subgroup of 80, no mutation was identified in the FVIII gene. Therefore, mutations in non-coding areas or even in other genes have to be considered responsible for the haemophilia A like phenotype. One of them codes for the von Willebrand factor (vWF). We confirmed in two of our cases mutations in the vWF gene.

Base Sequence↗
PubMed2002

Remission of thrombotic thrombocytopenic purpura in a patient with compound heterozygous deficiency of von Willebrand factor-cleaving protease by infusion of solvent/detergent plasma.

UNLABELLED: Plasma exchange or plasma infusion is considered to be the therapy of choice in patients with thrombotic thrombocytopenic purpura (TTP) who are deficient in von Willebrand factor-cleaving protease (VWF-CP). Recently, mutations in the ADAMTS 13 gene were identified as being responsible for VWF-CP deficiency in patients with familial TTP (VWF-CP deficiency in the absence of an inhibitor). Here we report on a girl who presented with recurrent thrombocytopenia and anaemia since birth, developing the full pentad of characteristic TTP at the age of 16 y. Congenital TTP was confirmed on the basis of severe VWF-CP deficiency in the absence of an acquired inhibitor. The patient was found to be compound heterozygous for two hitherto undescribed mutations in the ADAMTS 13 gene: a truncating frame shift mutation, 4143insA in exon 29, and the nonsense mutation 3100A >T in exon 24 (R1034X). After infusion of solvent/detergent plasma, the patient went into remission and remained asymptomatic under regular plasma therapy at 2-wk intervals for over two years. CONCLUSION: TTP in childhood may be mild and oligosymptomatic. Determination of VWF-CP activity is helpful in the differential diagnosis of thrombocytopenia.

ADAM Proteins↗
PubMed2001

Expression and characterization of von Willebrand factor dimerization defects in different types of von Willebrand disease.

Dimerization defects of von Willebrand factor (vWF) protomers underlie von Willebrand disease (vWD) type 2A, subtype IID (vWD 2A/IID), and corresponding mutations have been identified at the 3' end of the vWF gene in exon 52. This study identified and expressed 2 additional mutations in this region, a homozygous defect in a patient with vWD type 3 (C2754W) and a heterozygous frameshift mutation (8566delC) in a patient with vWD type 2A, subtype IIE. Both mutations involve cysteine residues that we propose are possibly essential for dimerization. To prove this hypothesis, transient recombinant expression of each of the 2 mutations introduced in the carboxy-terminal vWF fragment II and in the complete vWF complementary DNA, respectively, were carried out in COS-7 cells and compared with expression of vWD 2A/IID mutation C2773R and the wild-type (WT) sequence in COS-7 cells. Recombinant WT vWF fragment II assembled correctly into a dimer, whereas recombinant mutant fragments were monomeric. Homozygous expression of recombinant mutant full-length vWF resulted in additional dimers, probably through disulfide bonding at the amino-terminal multimerization site, whereas recombinant WT vWF correctly assembled into multimers. Coexpression of recombinant mutant and recombinant WT vWF reproduced the multimer patterns observed in heterozygous individuals. Our results suggest that a common defect of vWF biosynthesis--lack of vWF dimerization--may cause diverse types and subtypes of vWD. We also confirmed previous studies that found that disulfide bonding at the vWF amino-terminal is independent of dimerization at the vWF carboxy-terminal. (Blood. 2001;97:2059-2066)

Adult↗
PubMed2001

Familial Williams-Beuren syndrome showing varying clinical expression.

Williams-Beuren syndrome (WBS) is a contiguous gene syndrome that occurs mainly sporadically, with an estimated frequency of 1:13,700 to 1:25,000 [Grimm and Wesselhoeft, 1980; Martin et al., 1984; Udwin, 1990]. The cases of monozygotic twins concordant for WBS and dizygotic twins discordant for the syndrome have been reported. In addition, a few familial cases have been described since 1993. The clinical diagnosis has been supported by molecular genetic findings in only two patients, however. We herein report on two families in which the WBS was inherited in girls from their mothers. All four patients showed the typical hemizygous deletion at 7q11.23 [46,XX, ish,del(7)(q11.23q11.23) (ELN/LIMK1/D7S-613x1, D7S486/D7S522x2)], but the clinical picture was strikingly variable within and between families.

Adolescent↗
PubMed2001

Screening strategies for a highly polymorphic gene: DHPLC analysis of the Fanconi anemia group A gene.

INTRODUCTION: Patients with Fanconi anemia (Fanc) are at risk of developing leukemia. Mutations of the group A gene (FancA) are most common. A multitude of polymorphisms and mutations within the 43 exons of the gene are described. To examine the role of heterozygosity as a risk factor for malignancies, a partially automatized screening method to identify aberrations was needed. We report on our experience with DHPLC (WAVE (Transgenomic)). METHODS: PCR amplification of all 43 exons from one individual was performed on one microtiter plate on a gradient thermocycler. DHPLC analysis conditions were established via melting curves, prediction software, and test runs with aberrant samples. PCR products were analyzed twice: native, and after adding a WT-PCR product. Retention patterns were compared with previously identified polymorphic PCR products or mutants. RESULTS AND DISCUSSION: We have defined the mutation screening conditions for all 43 exons of FancA using DHPLC. So far, 40 different sequence variations have been detected in more than 100 individuals. The native analysis identifies heterozygous individuals, and the second run detects homozygous aberrations. Retention patterns are specific for the underlying sequence aberration, thus reducing sequencing demand and costs. DHPLC is a valuable tool for reproducible recognition of known sequence aberrations and screening for unknown mutations in the highly polymorphic FancA gene.

Base Sequence↗