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R Schneppenheim

Publications and source records attributed to R Schneppenheim.

At least 19 recordsLinked to original sources
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↗
PubMed2001

Novel missense mutations outside the allosteric domain of glutamate dehydrogenase are prevalent in European patients with the congenital hyperinsulinism-hyperammonemia syndrome.

The hyperinsulinism-hyperammonemia syndrome (HHS) has been shown to result from 'gain-of-function' mutations of the glutamate dehydrogenase (GlDH) gene, GLUD1. In the original report, all mutations were found in a narrow range of 27 base pairs within exons 11 and 12 which predicted an effect on the presumed allosteric domain of the enzyme and all these mutations were associated by a diminished inhibitory effect of guanosine triphosphate (GTP) on GlDH activity. We have investigated 14 patients from seven European families with mild hyperinsulinism. In four families, more than one member was affected. In eight cases hyperammonemia was documented, and eight cases had signs of significant leucine sensitivity. In one of the families, a novel heterozygous missense mutation in exon 6 [c.833C>T (R221C)] was detected, and in all other cases from six unrelated families the novel heterozygous missense mutation c.978G>A (R269H) was found in exon 7. When GIDH activity was measured in lymphocytes isolated from affected patients, both mutations were shown to result in a normal basal activity but a diminished sensitivity to GTP. It is the first time that this effect is reported for mutations located in the presumed catalytic site and outside the GTP allosteric domain of the enzyme. The observation of the high prevalence of the exon 7 mutation both in familial and sporadic cases of HHS suggests a mutation hot spot and justifies a mutation screening for this novel mutation by mismatch PCR-based restriction enzyme digestion in patients with hyperinsulinism.

Adolescent↗
PubMed2001

Laboratory signs of activated coagulation are common in Henoch-Schönlein purpura.

We investigated 17 patients with Henoch-Schönlein purpura (HSP) and describe as yet unreported abnormal results of blood coagulation tests. In parallel to the activity of the disease, D-dimer concentrations in plasma were found to be significantly increased in 15 of the 17 patients; almost 50% of all patients showed values higher than 10 times the upper limit of the normal range. In 11 patients, plasma concentrations of thrombin-antithrombin complex (TAT) and prothrombin fragments 1 and 2 (F1+2) were examined; six of them showed abnormal results. The pathologic values were correlated to the activity of the disease, but abnormalities were also found in milder cases of HSP. These findings probably reflect local reactions within inflamed blood vessels rather than a systemic activation of coagulation and hyperfibrinolysis. Clinicians should be aware of these laboratory findings in order not to confuse common cases of HSP with purpura necroticans, a very severe type of vasculitis in which signs of disseminated intravascular coagulation (DIC) have been reported. Our findings suggest that an activation of coagulation including hyperfibrinolysis secondary to the endothelial damage is a typical feature of the common types of HSP.

Antithrombin III↗
PubMed2001

Molecular genetic basis and prevalence of glycogen storage disease type IIIA in the Faroe Islands.

Glycogen storage disease type IIIA (GSD IIIA) is caused by mutations of the amyloglucosidase gene (AGL). For most populations, none of the AGL mutations described to date is particularly frequent. In this paper, we report that six children with GSD IIIA from the Faroe Islands were found to be homozygous for the novel nonsense mutation c.1222C>T (R408X) of the AGL gene. This mutation is easily detected by restriction enzyme digest with NsiI after mismatch PCR. Investigating five intragenic polymorphisms, we could show that this mutation was always associated with the same haplotype. The c.1222C>T mutation could be detected on two chromosomes of another 50 unselected GSD IIIA patients of other European or North American origin which means that this mutation plays a minor role worldwide. From the fact that we are currently aware of a total of 14 GSD IIIA cases in the Faroese population of 45 000, the observed prevalence is 1 : 3100. While the novel AGL mutation c.1222C>T was not detectable among 198 German newborns, nine out of 272 children from the Faroese neonatal screening program were found to be heterozygous for this mutation. Thus, the calculated prevalence is 1 : 3600 (95% CI 1:700-1:6400). We conclude that due to a founder effect, the Faroe Islands have the highest prevalence of GSD IIIA world-wide. The detection of the molecular defect has facilitated the diagnosis and has offered the opportunity for prenatal diagnosis in this patient group.

Codon, Nonsense↗
PubMed2001

Von Willebrand factor and 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 weight glycoprotein. Typically, it affects the primary hemostatic system, which results in a mucocutaneous bleeding tendency simulating a platelet function defect. The vWF promotes its function in two ways: (i) by initiating platelet adhesion to the injured vessel wall under conditions of high shear forces, and (ii) by its carrier function for factor VIII in plasma. Accumulating knowledge of the different clinical phenotypes and the pathophysiological basis of the disease translated into a classification 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 conducting genotype-phenotype studies which have recently helped, not only to elucidate or confirm important functions of vWF and its steps in post-translational processing, but also many disease causing defects. Acquired von Willebrand syndrome (avWS) has gained more attention during the recent years. An international registry was published and recommendation by the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis in 2000. It concluded that avWS, although not a frequent disease, is nevertheless probably underdiagnosed. This should be addressed in future prospective studies. The aim of treatment is the correction of the impaired hemostatic system of the patient, ideally including the defects of both primary and secondary hemostasis. Desmopressin is the treatment of choice in about 70% of patients, mostly with type 1, while the others merit treatment with concentrates containing vWF.

Clinical Laboratory Techniques↗
PubMed2001

A molecular approach to the classification of von Willebrand disease.

The marked heterogeneity of von Willebrand disease was already recognized by von Willebrand in 1926. The accumulating knowledge of the different clinical phenotypes and the pathophysiological basis of the disease was translated into a classification that differentiated between quantitative and qualitative defects by means of quantitative and functional parameters and by analysing the electrophoretic pattern of von Willebrand factor multimers. The increasing number of different von Willebrand disease phenotypes required a revision of the nomenclature at a time when only a few types of von Willebrand disease had already been analysed at the molecular level. Consequently, the molecular data played only a minor role in the revised classification. Given the pronounced, even intra-individual, variation in the manifestation of von Willebrand disease and the diagnostic difficulties caused by a non-standardized methodology, it is clear that biochemical methods alone are insufficient for a clear classification. The advent of molecular techniques provided the opportunity for genotype-phenotype studies that recently helped to elucidate or confirm not only the important functions of von Willebrand factor and the steps of its 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 final classification of von Willebrand disease, equally useful for the clinician and for research requirements.

Genetic Variation↗
PubMed2001

Quantification and facilitated comparison of von Willebrand factor multimer patterns by densitometry.

The analysis of von Willebrand factor (vWF) multimers is an important laboratory tool for distinguishing among the numerous subtypes of von Willebrand disease (vWD). Comparability and reproducibility of this method are insufficient; standardization and external references are pending. Interlaboratory comparison of results therefore may be difficult. We applied densitometry to obtain a reproducible quantification of vWF multimer patterns in healthy donors, patients with vWD variants, and factor VIII/vWF concentrates to improve the reproducibility and comparability of vWF multimer analysis. Multimers were separated and visualized luminographically on x-ray films. Films were scanned and evaluated by densitometry. The variation inherent in vWF multimer analysis and the range of the normal could be quantified. In vWD variants and factor VIII/vWF concentrates, densitometry could quantify and visualize alterations of vWF multimer patterns and facilitate their comparison. Densitometry permits a precise quantitative comparison of sample patterns to a reference plasma. It could be a valuable tool offering reproducible quantification and additional visualization of normal and pathologic vWF multimer patterns, facilitating their comparison and contributing to a standardization of vWF multimer analysis.

Adult↗