Molecular Genetics of von Willebrand Disease in Korean Patients: Novel Variants and Limited Diagnostic Utility of Multiplex Ligation-Dependent Probe Amplification Analyses

BACKGROUND: von Willebrand disease (VWD), characterized by quantitative or qualitative defects of von Willebrand factor (VWF), is the most common inheritable bleeding disorder. Data regarding the genetic background of VWD in Korean patients is limited. To our knowledge, this is the first comprehensive molecular genetic investigation of Korean patients with VWD. METHODS: Twenty-two unrelated patients with VWD were recruited from August 2014 to December 2017 (age range 28 months–64 years; male:female ratio 1.2:1). Fifteen patients had type 1, six had type 2, and one had type 3 VWD. Blood samples were collected for coagulation analyses and molecular genetic analyses from each patient. Direct sequencing of all exons, flanking intronic sequences, and the promoter of VWF was performed. In patients without sequence variants, multiplex ligation-dependent probe amplification (MLPA) was performed to detect dosage variants. We adapted the American College of Medical Genetics and Genomics guidelines for variant interpretation and considered variants of uncertain significance, likely pathogenic variants, and pathogenic variants as putative disease-causing variants. RESULTS: VWF variants were identified in 15 patients (68%): 14 patients with a single heterozygous variant and one patient with two heterozygous variants. The variants consisted of 13 missense variants, one small insertion, and one splicing variant. Four variants were novel: p.S764Efs*16, p.C889R, p.C1130Y, and p.W2193C. MLPA analysis in seven patients without reportable variants revealed no dosage variants. CONCLUSIONS: This study revealed the spectrum of VWF variants, including novel ones, and limited diagnostic utility of MLPA analyses in Korean patients with VWD.

Genetic and prenatal diagnosis of a pedigree affected with type 3 von Willebrand disease / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To provide genetic and prenatal analysis for a pedigree affected with type 3 von Willebrand disease.</p><p><b>METHODS</b>Next generation sequencing and Sanger sequencing of the VWF gene were carried out for the pedigree. Suscepted pathogenic mutation was verified among other members of the pedigree and 100 healthy controls. Prenatal diagnosis was performed on amniotic cells derived from the fetus.</p><p><b>RESULTS</b>A homozygous mutation c.7287+1G>A of the VWF gene was detected in the patient, which was predicted by bioinformatic analysis as a pathological splice site mutation. The parents and sister of the patient have all carried the same mutation. The mutation was not detected among the 100 healthy controls. Prenatal diagnosis confirmed that the fetus did not inherit the same mutation.</p><p><b>CONCLUSION</b>A novel mutation of the VWF gene was discovered, which correlated with the phenotype of the patient. Based on the discovery, prenatal diagnosis was provided for a fetus during subsequent pregnancy.</p>

Phenotype and genotype analysis of two Chinese pedigrees with type 3 von Willebrand diseases / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze the phenotype and genotype of two Chinese pedigrees with von Willebrand diseases, and to investigate the molecular pathogenesis.</p><p><b>METHODS</b>Bleeding time (BT), activated partial thromboplastin time (APTT), ristocetin-induced platelet aggregation (RIPA), von Willebrand factor-ristocetin cofactor (vWF:Rco), von Willebrand factor antigen (vWF:Ag), von Willebrand factor activity (vWF:A), von Willebrand factor collagen binding assay (vWF:CB) and multimer analysis were used for phenotype diagnosis. DNA was extracted. All of the 52 exons and exon-intron bounda ries of the VWF gene were amplified with polymerase chain reaction(PCR) and analyzed by direct sequencing.</p><p><b>RESULTS</b>APTT and BT were prolonged. Plasma RIPA, vWF:Rco, vWF:Ag, vWF:A and vWF:CB was significantly decreased. No VWF multimer can be found by plasma VWF multimer analysis. Homozygous insertional mutation g.82888_82889insCATG in exon 17 was found in proband A. Compound heterozygous mutations g.94865 G to A (Trp856stop) in exon 20 and g.110698_110699delinsG in exon 28 were found in proband B.</p><p><b>CONCLUSION</b>Homozygous insertional mutation g.82888_82889insCATG and compound heterozygous mutations g.94865G to A(Trp856X) and g.110698_110699delinsG probably have respectively induced type 3 von Willebrand diseases in the two probands.</p>

Subtypes of von Willebrand Disease Based on vWF Multimer Analysis in Korea / 대한소아혈액종양학회지

PURPOSE: von Willebrand disease is a common inherited bleeding disorder characterized by high degree of variable clinical presentation due to either quantitative or qualitative defects in von Willebrand factor. Its incidence in Korea is not well studied while that in western countries is extensively studied. METHODS: We classified 16 cases of vWD from 14 unrelated families based on vWF antigen, ristocetin cofactor activity, factor VIII activity and vWF multimeric patterns analysed by agarose gel electrophoresis, according to a revised classification by ISTH. RESULTS: There were 12 cases (75%) of type 1 vWD or 2M/2N with normal multimeric pattern, 3 cases (18.75%) of type 2 vWD lacking high molecular weight multimers and only 1 case of type 3 vWD with no multimers. CONCLUSION: The proportion of each vWD subtype in Korea is similar to that in western countries, however, accurate diagnosis based on ristocetin induced platelet aggregation test, factor VIII binding assay and molecular genetic diagnosis seems to be necessary for a more complete classification of vWD.