Unraveling the Influence of Common von Willebrand factor variants on von Willebrand Disease Phenotype: An Exploratory Study on the Molecular and Clinical Profile of von Willebrand Disease in Spain Cohort.

The clinical diagnosis of von Willebrand disease (VWD), particularly type 1, can be complex because several genetic and environmental factors affect von Willebrand factor (VWF) plasma levels. An estimated 60% of the phenotypic variation is attributable to hereditary factors, with the ABO blood group locus being the most influential. However, recent studies provide strong evidence that nonsynonymous single nucleotide variants (SNVs) contribute to VWF and factor VIII phenotypic variability in healthy individuals. This study aims to investigate the role of common VWF SNVs on VWD phenotype by analyzing data from 219 unrelated patients included in the "Molecular and Clinical Profile of von Willebrand Disease in Spain project." To that end, generalized linear mixed-effects regression models were fitted, and additive and epistatic analyses, and haplotype studies were performed, considering five VWD-related measures (bleeding score, VWF:Ag, VWF:RCo, factor VIII:C, and VWF:CB). According to these analyses, homozygotes: for p.Thr789Ala(C) would be expected to show 39% higher VWF:Ag levels; p.Thr1381Ala(C), 27% lower VWF:Ag levels; and p.Gln852Arg(C), 52% lower VWF:RCo levels. Homozygotes for both p.Thr789Ala(C) and p.Gln852Arg(T) were predicted to show 185% higher VWF:CB activity, and carriers of two copies of the p.Thr1381Ala(T)/p.Gln852Arg(T) haplotype would present a 100% increase in VWF:RCo activity. These results indicate a substantial effect of common VWF variation on VWD phenotype. Although additional studies are needed to determine the true magnitude of the effects of SNVs on VWF, these findings provide new evidence regarding the contribution of common variants to VWD, which should be taken into account to enhance the accuracy of the diagnosis and classification of this condition. ClinicalTrials.gov identifier: NCT02869074.

Factor XIII deficiency in two Spanish families with a novel variant in gene F13A1 detected by next-generation sequencing; symptoms and clinical management.

Coagulation factor XIII (FXIII) has a major role in coagulation stabilizing the haemostatic clot. FXIII deficiency is associated with an increased risk of bleeding. Severe phenotypes lead to spontaneous, traumatic and surgical bleeding. Umbilical cord bleeding is especially common, and intracranial bleeding may occur in up to one third of patients without prophylaxis. In this work, we used NGS for screening all the coding and intronic boundary regions of F13A1 and F13B genes in two families affected by severe FXIII deficiency. Outcome confirmation analysis and variant studies in related patients was done by Sanger sequencing. Two variants were found: c.34A > G (p.Arg12Gly; NM_00129.3) and c.514C > T (p.Arg172Ter; NM_00129.3), both located in the F13A1 gene. The variant p.Arg172Ter is already described in literature and was found in homozygosis in one family and in compound heterozygosis in the other family. The variant p.Arg12Gly variant has not been described previously. This variant is located in the activation peptide of the FXIII A-subunit which is highly conserved among FXIII homologs. Given the high risk of dangerous bleeding and early manifestation in severe FXIII-deficient patients, a prompt genetic confirmation is imperative. In this sense, NGS technology allows a rapid and simultaneous analysis of all regions of all the genes involved in the pathology.

Involvement of antifactor VIII autoantibodies specificity in the outcome of inhibitor eradication therapies in acquired hemophilia a patients.

: We hypothesized that inhibitor specificity may predict the outcome of antifactor VIII autoantibodies eradication treatment in acquired hemophilia A. Our objective was to analyze the association between factor VIII domains recognized by inhibitors and outcome of the immunosuppressive therapies (ISTs) in a prospective, observational study. 16 patients were recruited. Inhibitor specificities were assessed at diagnosis and throughout the study. Their association with IST outcome was addressed. First-line IST succeeded in 56% of patients. Inhibitors reacted mainly with light chain domains (69%) and/or the A2 domain (44%). 31% inhibitors recognized more than one domain. Significantly, the number of patients whose inhibitors recognized the light chain was significantly higher in the group of those who did not reach complete remission after first line IST when compared with those who did [6/7 (85.7%) vs. 4/9 (44.4%), P < 0.05]. Therefore, inhibitor specificity could predict the success of IST in acquired hemophilia A.

Unraveling the effect of silent, intronic and missense mutations on VWF splicing: contribution of next generation sequencing in the study of mRNA.

Large studies in von Willebrand disease patients, including Spanish and Portuguese registries, led to the identification of >250 different mutations. It is a challenge to determine the pathogenic effect of potential splice site mutations on VWF mRNA. This study aimed to elucidate the true effects of 18 mutations on VWF mRNA processing, investigate the contribution of next-generation sequencing to in vivo mRNA study in von Willebrand disease, and compare the findings with in silico prediction. RNA extracted from patient platelets and leukocytes was amplified by RT-PCR and sequenced using Sanger and next generation sequencing techniques. Eight mutations affected VWF splicing: c.1533+1G>A, c.5664+2T>C and c.546G>A (p.=) prompted exon skipping; c.3223-7_3236dup and c.7082-2A>G resulted in activation of cryptic sites; c.3379+1G>A and c.7437G>A) demonstrated both molecular pathogenic mechanisms simultaneously; and the p.Cys370Tyr missense mutation generated two aberrant transcripts. Of note, the complete effect of three mutations was provided by next generation sequencing alone because of low expression of the aberrant transcripts. In the remaining 10 mutations, no effect was elucidated in the experiments. However, the differential findings obtained in platelets and leukocytes provided substantial evidence that four of these would have an effect on VWF levels. In this first report using next generation sequencing technology to unravel the effects of VWF mutations on splicing, the technique yielded valuable information. Our data bring to light the importance of studying the effect of synonymous and missense mutations on VWF splicing to improve the current knowledge of the molecular mechanisms behind von Willebrand disease. clinicaltrials.gov identifier:02869074.

Guía práctica de tratamiento urgente de la microangiopatía trombótica / Practice guidelines for the emergency treatment of thrombotic microangiopathy

Antecedentes y objetivo: El término microangiopatía trombótica (MAT) incluye un grupo heterogéneo de enfermedades potencialmente mortales o invalidantes, rápidamente evolutivas, caracterizadas por anemia hemolítica microangiopática y trombocitopenia. La actuación en las primeras horas es crucial para mejorar el pronóstico de los pacientes. El objetivo de esta revisión es proporcionar recomendaciones orientadas a optimizar el tratamiento inicial de la MAT y agilizar el diagnóstico etiológico. Pacientes y métodos: Se diseña una guía práctica en la cual se diferencian cuatro apartados en el abordaje inicial de las MAT: sospecha diagnóstica, confirmación sindrómica, tratamiento urgente y estudios complementarios. Resultados: La detección de anemia hemolítica microangiopática (caracterizada por aumento de reticulocitos, LDH y bilirrubina indirecta, Coombs directo negativo y esquistocitos en el frotis de sangre periférica) y trombocitopenia no justificable por otras causas secundarias confirma el diagnóstico sindrómico de anemia hemolítica microangiopática y trombocitopenia (AHMAT). Estos pacientes requieren ingreso en la unidad de cuidados intensivos para iniciar lo antes posible el recambio plasmático, preferiblemente en las primeras 4-8h. Antes de realizar el recambio plasmático deben extraerse las muestras para el estudio de ADAMTS13 y de complemento. Finalmente, es importante solicitar las pruebas complementarias necesarias para obtener un correcto diagnóstico etiológico. Conclusiones: La puesta en práctica de las recomendaciones consensuadas en esta guía permitirá mejorar los resultados terapéuticos al facilitar la cooperación de los distintos especialistas implicados en la atención de las MAT

Background and aim: The term thrombotic microangiopathy (TMA) involves a heterogeneous group of diseases that can be overwhelming or invalidating, with an acute development, characterised by microangiopathic haemolytic anaemia and thrombocytopaenia. Its management during its initial hours is essential to improving the prognostic of these patients. The aim of this review is to give recommendations about the optimisation of TMA initial treatment and to accelerate the aetiological diagnosis. Patients and methods: We provide a practice guideline based on four steps for the initial management of TMA: diagnosis of suspicion, syndromic confirmation, emergent treatment and complementary tests. Results: The detection of microangiopathic haemolytic anaemia (characterised by elevated reticulocytes, LDH and indirect bilirubin, negative direct Coombs test and schistocytes in peripheral blood), and thrombocytopaenia not explained by other secondary aetiologies confirm the syndromic diagnosis of microangiopathic haemolytic anaemia and thrombocytopaenia (MAHAT). These patients require admission to an Intensive Care Unit to initiate plasma exchange therapy as soon as possible, ideally within the first 4-8hours. Prior to this, samples for ADAMTS13 and complement study should be obtained. Finally, it is important to request the complementary tests necessary to have a correct aetiological diagnosis. Conclusions: Adherence to the agreed recommendations in this guideline will improve therapeutic results by facilitating cooperation between different specialists involved in TMA management

Role of multimeric analysis of von Willebrand factor (VWF) in von Willebrand disease (VWD) diagnosis: Lessons from the PCM-EVW-ES Spanish project.

The multimeric analysis (MA) of plasma von Willebrand factor (VWF) evaluates structural integrity and helps in the diagnosis of von Willebrand disease (VWD). This assay is a matter of controversy, being considered by some investigators cumbersome and only slightly informative. The centralised study 'Molecular and Clinical Profile of von Willebrand Disease in Spain (PCM-EVW-ES)' has been carried out by including the phenotypic assessment and the genetic analysis by next generation sequencing (NGS) of the VWF gene (VWF). The aim of the present study was to evaluate the role of MA to the diagnosis of these patients and their potential discrepancies. Two hundred and seventy out of 480 patients centrally diagnosed with VWD had normal multimers, 168 had abnormal multimers and 42 a total absence of multimers. VWF MA was of great significance in the diagnosis of 83 patients (17.3%), it was also of help in the diagnosis achieved in 365 additional patients (76%) and was not informative in 32 cases (6.7%). With regard to discrepancies, 110 out of 480 (23%) patients centrally diagnosed with VWD presented some kind of discordance between VWF:RCo/VWF:Ag and/or VWF:CB/VWF:Ag ratios, multimeric study and/or genetic results. The VWF MA was key in the presence of novel mutations as well as in cases with phenotypic discrepancies. A comparison between the contribution of MA and VWF:CB showed a clearly higher contribution of the former in the diagnostic process. These data seem to reinforce the relevance of the VWF MA in VWD diagnosis, despite all its limitations.

Practice guidelines for the emergency treatment of thrombotic microangiopathy. / Guía práctica de tratamiento urgente de la microangiopatía trombótica.

BACKGROUND AND AIM: The term thrombotic microangiopathy (TMA) involves a heterogeneous group of diseases that can be overwhelming or invalidating, with an acute development, characterised by microangiopathic haemolytic anaemia and thrombocytopaenia. Its management during its initial hours is essential to improving the prognostic of these patients. The aim of this review is to give recommendations about the optimisation of TMA initial treatment and to accelerate the aetiological diagnosis. PATIENTS AND METHODS: We provide a practice guideline based on four steps for the initial management of TMA: diagnosis of suspicion, syndromic confirmation, emergent treatment and complementary tests. RESULTS: The detection of microangiopathic haemolytic anaemia (characterised by elevated reticulocytes, LDH and indirect bilirubin, negative direct Coombs test and schistocytes in peripheral blood), and thrombocytopaenia not explained by other secondary aetiologies confirm the syndromic diagnosis of microangiopathic haemolytic anaemia and thrombocytopaenia (MAHAT). These patients require admission to an Intensive Care Unit to initiate plasma exchange therapy as soon as possible, ideally within the first 4-8hours. Prior to this, samples for ADAMTS13 and complement study should be obtained. Finally, it is important to request the complementary tests necessary to have a correct aetiological diagnosis. CONCLUSIONS: Adherence to the agreed recommendations in this guideline will improve therapeutic results by facilitating cooperation between different specialists involved in TMA management.

Molecular and clinical profile of von Willebrand disease in Spain (PCM-EVW-ES): comprehensive genetic analysis by next-generation sequencing of 480 patients.

Molecular diagnosis of patients with von Willebrand disease is pending in most populations due to the complexity and high cost of conventional molecular analyses. The need for molecular and clinical characterization of von Willebrand disease in Spain prompted the creation of a multicenter project (PCM-EVW-ES) that resulted in the largest prospective cohort study of patients with all types of von Willebrand disease. Molecular analysis of relevant regions of the VWF, including intronic and promoter regions, was achieved in the 556 individuals recruited via the development of a simple, innovative, relatively low-cost protocol based on microfluidic technology and next-generation sequencing. A total of 704 variants (237 different) were identified along VWF, 155 of which had not been previously recorded in the international mutation database. The potential pathogenic effect of these variants was assessed by in silico analysis. Furthermore, four short tandem repeats were analyzed in order to evaluate the ancestral origin of recurrent mutations. The outcome of genetic analysis allowed for the reclassification of 110 patients, identification of 37 asymptomatic carriers (important for genetic counseling) and re-inclusion of 43 patients previously excluded by phenotyping results. In total, 480 patients were definitively diagnosed. Candidate mutations were identified in all patients except 13 type 1 von Willebrand disease, yielding a high genotype-phenotype correlation. Our data reinforce the capital importance and usefulness of genetics in von Willebrand disease diagnostics. The progressive implementation of molecular study as the first-line test for routine diagnosis of this condition will lead to increasingly more personalized and effective care for this patient population.

Molecular and clinical profile of von Willebrand disease in Spain (PCM-EVW-ES): Proposal for a new diagnostic paradigm.

The diagnosis of von Willebrand disease (VWD) remains difficult in a significant proportion of patients. A Spanish multicentre study investigated a cohort of 556 patients from 330 families who were analysed centrally. VWD was confirmed in 480. Next generation sequencing (NGS) of the whole coding VWF was carried out in all recruited patients, compared with the phenotype, and a final diagnosis established. A total of 238 different VWF mutations were found, 154 were not included in the Leiden Open Variation Database (LOVD). Of the patients, 463 were found to have VWF mutation/s. A good phenotypic/genotypic association was estimated in 96.5% of the patients. One hundred seventy-four patients had two or more mutations. Occasionally a predominant phenotype masked the presence of a second abnormality. One hundred sixteen patients presented with mutations that had previously been associated with increased von Willebrand factor (VWF) clearance. RIPA unavailability, central phenotypic results disagreement and difficult distinction between severe type 1 and type 3 VWD prevented a clear diagnosis in 70 patients. The NGS study facilitated an appropriate classification in 63 of them. The remaining seven patients presented with a VWF novel mutation pending further investigation. In five patients with a type 3 and two with a type 2A or 2B phenotype with no mutation, an acquired von Willebrand syndrome (AVWS) was suspected/confirmed. These data seem to support NGS as a first line efficient and faster paradigm in VWD diagnosis.

Novel missense mutation c.2685G>C (p.Q895H) in VWF gene associated with very low levels of VWF mRNA.

Homozygous patients for null alleles in VWF gene show a severe von Willebrand phenotype, whereas compound heterozygous patients only show the phenotype of the expressed allele. Five members of the same family were studied. The two patients showed borderline VWF levels, a mild factor VIII (FVIII) deficiency and a decrease of the binding of VWF to exogenous FVIII. The genetic analyses of the VWF gene confirmed that the patients were compound heterozygous for c.2561G>A (R854Q) and c.2685G>C (p.Q895H) mutations. The latter, is located in the 3' extreme of exon 20, and it has not been previously described. Studies of the cDNA from platelet mRNA were performed to investigate the expression of p.H895 allele. The loss of heterozygosity at the cDNA level suggests a lack of expression of the p.H895 allele. The overall studies can explain the type 2N phenotype of the two patients, since the allele carrying the new missense mutation p.Q895H has shown a low expression of VWF gene.