Significant linkage and non-linkage of type 1 von Willebrand disease to the von Willebrand factor gene (original) (raw)
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Journal of Thrombosis and Haemostasis, 2006
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%.
Blood, 2016
Von Willebrand disease (VWD) is the most common inherited bleeding disorder, and type 1 VWD is the most common VWD variant. Despite its frequency, diagnosis of type 1 VWD remains the subject of much debate. In order to study the spectrum of type 1 VWD in the United States, the Zimmerman Program enrolled 482 subjects with a previous diagnosis of type 1 VWD without stringent laboratory diagnostic criteria. VWF laboratory testing and full length VWF gene sequencing were performed for all index cases and healthy control subjects in a central laboratory. Bleeding phenotype was characterized using the ISTH Bleeding Assessment Tool. At study entry, 64% of subjects had VWF:Ag or VWF:RCo below the lower limit of normal, while 36% had normal VWF levels. VWF sequence variations were most frequent in subjects with VWF:Ag < 30 IU/dL (82%) while subjects with type 1 VWD and VWF:Ag ≥ 30 IU/dL had an intermediate frequency of variants (44%). Subjects whose VWF testing was normal at study entry h...
International Journal of General Medicine
Introduction: von Willebrand disease (VWD) is the most prevalent bleeding disease, which is associated with either low levels of von Willebrand factor (VWF) or abnormality in its structure. Three types of the disease have been described; type 1 (VWD1) and 3 (VWD3) are caused by deficiency of VWF and type 2 (VWD2) is caused by production of defective VWF. The aim of the current study was to characterize gene variants of VWF gene; exon 18 in particular, in a cohort of Saudi families as well as healthy control subjects. Methods: A total of 19 families comprising 60 subjects of type 1 VWD were enrolled in the study. Participants were divided into 22 index cases, 21 affected family members and 17 unaffected family members ranging in age from 6 to 70 years. Blood samples were collected from all participants to measure activated partial thromboplastin time test (APTT), von Willebrand antigen level (VWF:Ag), Factor VIII activity (FVIII:C) and ristocetin cofactor activity (VWF:RCo), platelet count, determining the ABO blood group and for genetic analysis by Sanger sequencing. Results: The results indicated that VWD1 patients have lower levels of VWF and factor VIII than the non-affected family members and the control subjects. In addition, five gene variants were reported in VWF exon 18; of these, c.2365A>G and c.2385T>C were more common in the control group and might be protective from VWD. Discussion: In conclusion, VWF levels are influenced by blood group, and there was no association between variants in exon 18 of VWF gene reported in all groups and the disease status; however, blood group analysis and genome-wide genotyping could help to highlight high-risk groups and improve clinical management of VWD.
Journal of Thrombosis and Haemostasis, 2011
Background: Type 3 von Willebrand disease (VWD) is an autosomal recessive bleeding disorder, characterized by virtually undetectable plasma von Willebrand factor (VWF) and consequently reduced plasma factor VIII levels. Genetic mutations responsible for type 3 VWD are very heterogeneous, scattered throughout the VWF gene and show high variability among different populations. Methods: Twenty-five severe VWD patients were studied by direct sequencing of the 51 coding exons of the VWF gene. The total number of VWD type 3 families in Hungary is 24, of which 23 were investigated. Results: Fifteen novel mutations were identified in 31 alleles, five being nonsense mutations (p.Q1238X, p.Q1898X, p.Q1931X, p.S2505X and p.S2568X), four small deletions and insertions resulting in frame shifts (c.1992insC, c.3622delT, c.5315insGA and c.7333delG), one a large partial deletion (delExon1-3) of the 5¢-region, four candidate missense mutations (p.C35R, p.R81G, p.C295S, p.C623T) and one a candidate splice site mutation (c.1730-10C>A). Six previously described mutations were detected in 17 alleles, including the repeatedly found c.2435delC, p.R1659X and p.R1853X. Only one patient developed alloantibodies to VWF, carrying a homozygous c.3622delT. Conclusion: We report the genetic background of the entire Hungarian type 3 VWD population. A large novel deletion, most probably due to a founder effect, seems to be unique to Hungarian type 3 VWD patients with high allele frequency. In contrast to previous reports, none of the five patients homozygous for the large partial deletion developed inhibitors to VWF. This discrepancy raises the possibility of selection bias in some of the reports.