von Willebrand disease with G4022A mutation (vWd Sungnam): a case report.
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A 10-year-old male patient affected by type 2 von Willebrand disease (vWD) and his family members were investigated by hemostatic and molecular genetic studies. The propositus, who experienced frequent bleeding episodes, was characterized by a normal level of von Willebrand factor (vWF) antigen (54%), reduced vWF ristocetin cofactor activity (5%), decreased factor VIII clotting activity (25%) and absent high molecular weight multimers in the plasma. An exon 28 fragment coding for the A1 and A2 domains was amplified by polymerase chain reaction and sequenced. We found a heterozygous mutation (G4022A), producing an additional PstI restriction site, which resulted in the substitution of Arg578Gln. Family studies, including the parents and a brother, were negative for this mutation and vWF abnormalities were not observed. We confirmed that G to A mutation in the region of the platelet glycoprotein Ib binding domain of vWF causes the qualitative type 2 defect in von Willebrand disease. (+info)
An acutely painful elbow as a first presentation of von Willebrand's disease.
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A 26 year old woman presented to the accident and emergency department with a painful right elbow. There had been no history of trauma. Clinical examination suggested an effusion, which was confirmed on radiological examination. Her elbow was aspirated and revealed a haemarthrosis. Subsequent investigations revealed a diagnosis of von Willebrand's disease (vWD). A spontaneously occurring effusion of the elbow may be due to a haemarthrosis. Aspiration of blood in the absence of trauma may lead to a diagnosis of an occult coagulopathy in addition to relieving pain. The diagnosis and treatment of vWD is discussed. (+info)
Low platelet alpha2beta1 levels in type I von Willebrand disease correlate with impaired platelet function in a high shear stress system.
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Platelet adhesion to collagen-coated surfaces in whole blood under flow conditions is mediated by both von Willebrand factor (vWF)-dependent recruitment of the platelet glycoprotein Ib-IX receptor complex and collagen interaction with the integrin alpha2beta1. In type 1 von Willebrand disease (vWD), platelet adhesive functions are impaired due to the decrease in vWF levels in plasma and platelets. There are at least three alleles of the human alpha2 gene, distinguishable by a cluster of silent or noncoding sequence differences within a segment of the gene. Two alleles, associated with low receptor density can be distinguished by nucleotide 807C, while the third allele associated with high receptor density, expresses nucleotide 807T. Gene frequencies of these alleles in a normal population (n = 167) are 0.58 for 807C and 0.42 for 807T. We measured the frequencies of these alleles in symptomatic patients with five types of vWD (type 1, n = 78; type 2A, n = 25, type 2B, n = 14; type 2M, n = 10; and type 3, n = 20). Compared with the normal group, no significant difference in allele frequencies was observed among individuals with types 2A, 2B, 2M, or 3 vWD. However, the frequency of the 807C allele, associated with low collagen receptor density, among type 1 vWD patients (807C =.71; 807T =.29) was significantly higher than that of the normal population (P =.007). Also, in patients with vWD type 1 and borderline to normal ristocetin-cofactor (vWF:RCo) activity values, collagen receptor density correlates inversely with closure time in a high shear stress system (platelet function analyzer [PFA-100]). We propose that low platelet alpha2beta1 density results in less efficient primary platelet adhesion and may result in increased tendency to bleed, as evidenced by the high frequency of this polymorphism in patients with type 1 vWD compared with normal individuals. In addition, this may account for the variability between patients with similar levels of vWF antigen, but strikingly different bleeding histories. (+info)
Plasma von Willebrand factor-collagen binding activity in normal dogs and in dogs with von Willebrand's disease.
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A sensitive enzyme-linked immunosorbent assay was used for the simultaneous assessment of the amount of von Willebrand factor (vWF) in canine plasma and its ability to bind to canine collagen in vitro. In 60 normal dogs, there was close correlation between the concentration of vWF and its activity as determined by vWF-collagen binding. In 14 dogs with type I expressions of von Willebrand's disease, the ratio of vWF antigen to collagen binding activity was normal or only slightly increased. In 7 dogs with type II expressions of the disease, this ratio was consistently elevated suggesting a significant functional deficiency of the protein. Plasma from 3 dogs with type III von Willebrand's disease had little collagen binding activity because of the severe quantitative deficiency of the protein. The described assay permits the rapid assessment of both the quantity and quality of vWF in a dog. This information is necessary for the detection and characterization of canine von Willebrand's disease, particularly the type II expressions, which cannot be diagnosed by quantitative vWF assays alone. (+info)
Evidence for extracellular processing of pro-von Willebrand factor after infusion in animals with and without severe von Willebrand disease.
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Although proteolytic processing of pro-von Willebrand factor (pro-vWF) resulting in free propeptide and mature vWF is known to be initiated intracellularly, vWF released from endothelial cells may contain a high proportion of incompletely processed pro-vWF. Because pro-vWF is only rarely detectable in normal human plasma, we investigated whether extracellular processing of pro-vWF is possible. A recombinant preparation (rpvWF) containing both pro-vWF and mature vWF subunits was infused into 2 pigs and 1 dog with severe von Willebrand disease, 2 mice with a targeted disruption of the vWF gene, and 2 healthy baboons. Total vWF antigen (vWF:Ag), free propeptide, and pro-vWF were measured using enzyme-linked immunosorbent assay techniques in blood samples drawn before and after infusion. vWF:Ag increased promptly. No pro-vWF could be detected when the first postinfusion sample was drawn after 30 minutes (pigs) or 60 minutes (mice), but pro-vWF was detectable for short periods when postinfusion samples were drawn after 15 minutes (dog) or 5 minutes (baboons). In contrast, free propeptide was increased at the first timepoint measured, suggesting that it was generated from the pro-vWF in the rpvWF preparation. vWF multimers were analyzed in the rpvWF preparation and in plasma samples drawn before and after infusion of rpvWF using ultra-high resolution 3% agarose gels to allow separation of homo- and hetero-forms of the vWF polymers. Within 30 minutes after infusion in the pigs, 1 hour in the dog and the mice, and within 2 hours in the baboons, the multimer pattern had changed to that typically seen in mature vWF. These data indicate that propeptide cleavage from unprocessed vWF can occur extracellularly in the circulation. The enzyme or enzymes responsible for this cleavage in plasma remain to be identified. (+info)
Desmopressin enhances the binding of plasma von Willebrand factor to collagen in plasmas from normal dogs and dogs with type I von Willebrand's disease.
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A new in vitro von Willebrand factor-collagen binding activity (vWF:CBA) assay was used to assess qualitative changes in vWF in normal dogs and dogs with Type I von Willebrand's disease (vWD) following treatment with desmopressin acetate (DDAVP). Although DDAVP induced increases in vWF antigen concentrations at 1 hour postinfusion in both normal and vWD dogs (57% and 60% increases, respectively), there were disproportionately greater increases in vWF:CBA (96% and 103% increases). These results support the hypothesis that the enhanced hemostatic activity induced by DDAVP is, at least in part, due to the selective release of more functionally active vWF multimers. The assay, as described, provides a convenient means of simultaneously assessing vWF quantity and function before and after DDAVP administration. (+info)
Involvement of low-density lipoprotein receptor-related protein (LRP) in the clearance of factor VIII in von Willebrand factor-deficient mice.
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Factor VIII is tightly noncovalently linked to von Willebrand factor (vWF) in plasma with a stoichiometry of 1:50, and vWF deficiency results in secondary factor VIII deficiency, with accelerated clearance of factor VIII from the circulation. We used a murine model of severe von Willebrand disease (vWF knockout mice) to study the effect of a recombinant vWF/pro-vWF preparation (rpvWF) on factor VIII survival and to investigate whether low-density lipoprotein receptor-related protein (LRP) might be involved in the in vivo clearance of factor VIII in the absence of vWF. vWF-deficient mice received 70 U/kg rpvWF in the first series of experiments, and in a second series, 80 mg/kg receptor-associated protein (RAP) as a recombinant fusion protein to block the action of LRP. Factor VIII levels were measured at time 0, or 1 or 3 hours after administration of rpvWF or RAP. RAP induced a sustained rise in factor VIII levels comparable to that induced by rpvWF. In a third series, the preadministration of RAP resulted in a slower disappearance of factor VIII antigen (measured by an enzyme-linked immunosorbent assay specific for human factor VIII) after infusion of recombinant factor VIII. These findings suggest that the accelerated clearance of factor VIII seen in the absence of vWF may be a result of the involvement of LRP in factor VIII metabolism. (Blood. 2000;95:1703-1708) (+info)
Two novel type 2N von Willebrand disease-causing mutations that result in defective factor VIII binding, multimerization, and secretion of von Willebrand factor.
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Two novel mutations, a T-to-C transition at nucleotide 2612 and a T-to-G transversion at nucleotide 3923 of the von Willebrand factor (vWF) complementary DNA, were detected by analysis of the vWF gene in DNA from members of 2 families with atypical von Willebrand disease. The T2612C transition predicts substitution of cysteine by arginine at amino acid position 788 (C788R), and the T3923G transversion predicts substitution of cysteine by glycine at position 1225 (C1225G) of pre-pro-vWF. The patients homozygous for the C788R and C1225G mutations both had a partial vWF deficiency (0. 18 IU/mL and 0.07 IU/mL vWF antigen, respectively); vWF in plasma from patients homozygous for either the C788R or the C1225G mutation failed to bind factor VIII and lacked high molecular weight multimers. Recombinant (r) vWF molecules having the C788R or C1225G mutation were expressed in COS-7 cells. Both rvWF C788R and rvWF C1225G exhibited significantly impaired secretion and failed to bind factor VIII. Recombinant vWF C788R in COS-7 culture medium showed a severe reduction in high molecular weight multimers, whereas rvWF C1225G showed a very mild reduction in high molecular weight multimers when compared with wild-type rvWF. (Blood. 2000;95:2000-2007) (+info)