Asunto(s)

Mutación , Enfermedades de von Willebrand , Humanos , Enfermedades de von Willebrand/genética

RESUMEN

Clinical interpretation of genetic variants in the context of the patient's phenotype is a time-consuming and costly process. In-silico analysis using in-silico prediction tools, and molecular modeling have been developed to predict the influence of genetic variants on the quality and/or quantity of the resulting translated protein, and in this way, to alert clinicians of disease likelihood in the absence of previous evidence. Our objectives were to evaluate the success rate of the in-silico analysis in predicting the disease-causing variants as pathogenic and the single-nucleotide variants as neutral, and to establish the reliability of in-silico analysis for determining pathogenicity or neutrality of von Willebrand factor gene-associated genetic variants. Using in-silico analysis, we studied pathogenicity in 31 disease-causing variants, and neutrality in 61 single-nucleotide variants from patients previously diagnosed as type 2 von Willebrand disease. Disease-causing variants and non-synonymous single-nucleotide variants were explored by in-silico tools that analyze the amino acidic sequence. Intronic and synonymous single-nucleotide variants were analyzed by in-silico methods that evaluate the nucleotidic sequence. We found a consistent agreement between predictions achieved by in-silico prediction tools and molecular modeling, both for defining the pathogenicity of disease-causing variants and the neutrality of single-nucleotide variants. Based on our results, the in-silico analysis would help to define the pathogenicity or neutrality in novel genetic variants observed in patients with clinical and laboratory phenotypes suggestive of von Willebrand disease.

Asunto(s)

Enfermedades de von Willebrand , Factor de von Willebrand , Humanos , Factor de von Willebrand/genética , Factor de von Willebrand/metabolismo , Relevancia Clínica , Reproducibilidad de los Resultados , Enfermedades de von Willebrand/diagnóstico , Enfermedades de von Willebrand/genética , Nucleótidos

RESUMEN

The von Willebrand disease (vWD) is the most common hereditary bleeding disorder caused by defects of the von Willebrand Factor (vWF), a large extracellular protein in charge of adhering platelets to sites of vascular lesions. vWF performs this essential homeostatic task via specific protein-protein interactions between the vWF A1 domain and the platelet receptor, the glycoprotein Ib alpha (GPIBα). The two naturally occurring vWF A1 domain mutations G1324A and G1324S, near the GPIBα binding site, induce a dramatic decrease in platelet adhesion, resulting in a bleeding disorder classified as type 2M vWD. However, the reason for the drastic phenotypic response induced by these two supposedly minor modifications remains unclear. We addressed this question using a combination of equilibrium-molecular dynamics (MD) and nonequilibrium MD-based free energy simulations. Our data confirms that both mutations maintain the highly stable Rossmann fold of the vWF A1 domain. G1324A and G1324S mutations hardly changed the per-residue flexibility of the A1 domain but induced a global conformational change affecting the region near the binding site to GPIBα. Furthermore, we observed two significant changes in the vWF A1 domain upon mutation, the global redistribution of the internal mechanical stress and the increased thermodynamic stability of the A1 domain. These observations are consistent with previously reported mutations increasing the melting temperature. Overall, our results support the idea of thermodynamic conformational restriction of A1-before the binding to GPIBα-as a crucial factor determining the loss-of-function of the G1324A(S) vWD mutants.

Asunto(s)

Enfermedades de von Willebrand , Factor de von Willebrand , Humanos , Sitios de Unión , Plaquetas/metabolismo , Unión Proteica , Termodinámica , Enfermedades de von Willebrand/genética , Factor de von Willebrand/química , Factor de von Willebrand/genética

Asunto(s)

Enfermedad de von Willebrand Tipo 2 , Enfermedades de von Willebrand , Genotipo , Humanos , Fenotipo , Enfermedad de von Willebrand Tipo 2/genética , Enfermedades de von Willebrand/diagnóstico , Enfermedades de von Willebrand/genética

RESUMEN

Type 2A and 2M von Willebrand disease (VWD) broadly show similar phenotypic parameters, but involve different pathophysiological mechanisms. This report presents the clinical and laboratory profiles of type 2A and type 2M patients genotypically diagnosed at one large center. Higher bleeding score values and a higher incidence of major bleeding episodes were observed in type 2A compared with type 2M, potentially reflective of the absence of large and intermediate von Willebrand factor (VWF) multimers in 2A. In type 2A, most of disease-causing variants (DCVs) appeared to be responsible for increased VWF clearance and DCV clustered in the VWF-A1 domain resulted in more severe clinical profiles. In type 2M, DCV in the VWF-A1 domain showed different laboratory patterns, related to either reduced synthesis or shortened VWF survival, and DCV in the VWF-A2 domain showed patterns related mainly to shortened survival. VWF-type 1 collagen binding/Ag (C1B/Ag) showed different patterns according to DCV location: in type 2A VWD, C1B/Ag was much lower when DCVs were located in the VWF-A2 domain. In type 2M with DCV in the VWF-A1domain, C1B/Ag was normal, but with DCV in the VWF-A2 domain, C1B/Ag was low. The higher frequency of major bleeding in VWD 2M patients with DCV in the VWF-A2 domain than that with DCV in the VWF-A1 domain could be a summative effect of abnormal C1B/Ag, on top of the reduced VWF-GPIb binding. In silico modeling suggests that DCV impairing the VWF-A2 domain somehow modulates collagen binding to the VWF-A3 domain. Concomitant normal FVIII:C/Ag and VWFpp/Ag, mainly in type 2M VWD, suggest that other nonidentified pathophysiological mechanisms, neither related to synthesis/retention nor survival of VWF, would be responsible for the presenting phenotype.

Asunto(s)

Enfermedad de von Willebrand Tipo 2 , Enfermedades de von Willebrand , Hemorragia , Humanos , Fenotipo , Enfermedad de von Willebrand Tipo 2/genética , Enfermedades de von Willebrand/genética , Factor de von Willebrand/genética

RESUMEN

INTRODUCTION: von Willebrand factor (VWF) is a multimeric plasma glycoprotein that plays an important role in haemostasis. von Willebrand disease (VWD) is an inherited heterogeneous bleeding disorder caused by either a quantitative or qualitative defect of VWF. Type 3 VWD, the most severe form of the disease, leads to complete quantitative VWF deficiency. AIM: The present study aims to investigate the molecular pathogenesis of type 3 VWD patients from Southern Brazil. METHODS: The VWF gene was sequenced in 26 cases clinically diagnosed with type 3 VWD by next-generation sequencing using Ion Torrent PGM. RESULTS: In 25 patients, we were able to identify both disease-causing variants. We identified 72 different variants: 31 intronic and 41 exonic. Five novel variants were found: c.6976+5G>T; c.6885_6886insC; c.3378C>T (p.Cys1126); c.3346_3347insCCA; and c.2503G>T (p.Glu835*). Variants p.Pro2063Ser and p.Arg324* co-segregated in 17 patients, 15 of them in homozygosity. CONCLUSION: Our results may contribute to the discussion on whether the variant p.Pro2063Ser is pathogenic or not. Finally, the presence of a common haplotype in patients bearing these two variants suggests a founder effect for this variant in our region.

Asunto(s)

Enfermedad de von Willebrand Tipo 3 , Factor de von Willebrand , Sustitución de Aminoácidos , Brasil , Hemostasis , Humanos , Enfermedad de von Willebrand Tipo 3/genética , Enfermedades de von Willebrand/genética , Factor de von Willebrand/genética

RESUMEN

von Willebrand disease type 2B (VWD2B) expresses gain-of-function mutations that enhance binding of an individual's von Willebrand factor (VWF) to its platelet ligand, glycoprotein Ib (GPIb), and which are usually identified by increased ristocetin-induced platelet aggregation (RIPA). We describe here the phenotypic profile of 38 genotypically selected VWD2B-affected family members (AFMs) belonging to 19 unrelated families. Major bleeding was observed in 68.4% of AFMs (previous to their diagnosis and registered by lifetime interviews), with a total of 46 episodes (1.21/patient), and was found to be highly related to the individual bleeding score and presence of thrombocytopenia, but otherwise unrelated to other laboratory parameters. Excessive muco-cutaneous bleeding symptoms were often reported, the most frequent of which comprised menorrhagia, epistaxis, easy bruising, and bleeding after teeth extraction/in oral cavity. Eight unaffected family members were also studied. The prevalence of VWD2B within families was 0.826, and the penetrance of mutations was complete, making it mandatory to study entire family sets to complete diagnostic profiles. Seven heterozygous missense mutations were found, the most common being p.V1316M. In the p.R1308C group, 75% of the AFMs showed absence of RIPA at 0.5 mg/mL, 66.6% of whom had VWF:RCo < 10 IU/dL, and 50% of whom had VWF:CB < 10 IU/dL. In the p.S1310F group, none of the AFMs had VWF:RCo/VWF:Ag < 0.6 (RCo/Ag), but 100% had VWF:CB/VWF:Ag < 0.6/(CB/Ag). Patients with p.P1266L and p.R1304V were characterized as atypical VWD2B. Two de novo mutations were found in four AFMs belonging to two families. We also describe a novel mutation: p.Y1258C. Of our patients, 70.5% had O blood group. In conclusion, a normal RCo/Ag and a negative RIPA at 0.5 mg/mL do not necessarily rule out a diagnosis of VWD2B.

Asunto(s)

Enfermedad de von Willebrand Tipo 2/genética , Enfermedades de von Willebrand/genética , Factor de von Willebrand/genética , Femenino , Genotipo , Humanos , Masculino , Mutación

RESUMEN

BACKGROUND: Von Willebrand disease is the most common inherited disorder of the coagulation proteins in humans. There are three types: 1, 2A, 2B, 2N, 2M and 3. It is associated with mutations on chromosome 12 in the region p13.2, encoding the von Willebrand factor (VWF), which is synthesized in endothelial cells and megakaryocytes. DISCUSSION: The VWF gene has been characterised using molecular biology techniques, which have acquired an important role in diagnosis von Willebrand disease, as well as in the investigation of alterations in other genes, which may be involved in regulating the synthesis, processing, and secretion of VWF. However, there are still no strategies to integrate the molecular biology diagnostic tests available. Analysis of VWF multimers is a methodology that meets the characteristics for diagnosis, but it is not easy to standardise. Considering that even in tertiary centres in our country, von Willebrand patients do not have a definitive diagnosis, it is necessary to implement these methodologies to study and improve diagnosis. CONCLUSIONS: Von Willebrand disease is highly heterogeneous due to the molecular mechanisms that produce the various clinical and laboratory phenotypes. In Mexico there are few studies related to this disease; therefore it is essential to conduct a comprehensive study including clinical, basic, and special testing laboratory tests, in order to establish a correct diagnosis, develop new therapeutic approaches, and offer the appropriate medical care and genetic counselling.

Asunto(s)

Enfermedades de von Willebrand/diagnóstico , Enfermedades de von Willebrand/genética , Humanos , Enfermedades de von Willebrand/clasificación , Factor de von Willebrand/genética

RESUMEN

La enfermedad de von Willebrand tipo plaquetario (PT-VWD) y tipo 2B (2B-VWD) son trastornos hemorrágicos raros, caracterizados por agregación plaquetaria a bajas concentraciones de ristocetina (RIPA). El diagnóstico diferencial no es fácil y representa un desafío. Hasta el presente, sólo se habían reportado cinco mutaciones en el gen GP1BA relacionadas con este desorden. Describimos aquí la sexta mutación relacionada con PT-VWD, en un paciente con sintomatología hemorrágica severa, macro-trombocitopenia, leve agregación plaquetaria espontánea, RIPA positivo a 0,3 y 0,4 mg/mL, VWF:RCo/VWF: Ag<0,2 y estudios discriminatorios positivos para PT-VWD. VWFpp/VWF: Ag resultó normal a diferencia del 2B-VWD que en algunas oportunidades resulta afectado. El exón 28 del gen VWF del paciente y su madre no reveló mutaciones. Identificamos una sustitución G>T en el nucleótido 3805 en el gen GP1BA del paciente, resultando en un cambio de Trp a Leu en el residuo 246 (p.W246L), en la región de la GPIBa que une al VWF. Esta mutación no se identificó en su madre ni en 100 controles sanos. Es considerada como dañina por análisis in sílico. Consideramos que esta sustitución es responsable del fenotipo PT-VWD del paciente. Dada la ausencia de la misma en los 100 normales estudiados, no se considera un polimorfismo

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Platelet-type von Willebrand disease (PT-VWD) and type 2B von Willebrand disease (2B-VWD) are rare bleeding disorders characterized by increased ristocetin-induced platelet aggregation (RIPA) at low concentrations. Diagnosis of either condition is not easy and the differential diagnosis is especially challenging. Five mutations in the GP1BA gene related to PT-VWD and near 50 patients are currently reported worldwide. We herein describe a patient with severe bleeding symptoms, macro thrombocytopenia, mild spontaneous platelet aggregation, positive RIPA at 0.3 and 0.4 mg/mL, VWF: RCo/VWF: Ag <0.2, normal VWFpp/VWF: Ag ratio, and RIPA mixing tests and cryoprecipitate challenge positive for PT-VWD. GP1BA gene was studied in the patient, his mother, and 100 healthy control subjects. We identified a substitution G>T at nucleotide 3805 in the patient's GP1BA gene, resulting in a Trp to Leu amino acid change at residue 246 (p.W246L), within the VWF binding region. This mutation was absent in his unaffected mother and also in the 100 controls, and was predicted as damaging by in silico analysis. The residue is located in a strongly conserved position in the phylogenetic tree. These findings argue in favor of considering this substitution does not represent a polymorphism, and is therefore responsible for the PT-VWD phenotype of the patient

Asunto(s)

Humanos , Masculino , Enfermedades de von Willebrand/genética , Complejo GPIb-IX de Glicoproteína Plaquetaria/genética , Predisposición Genética a la Enfermedad/genética , Mutación Missense , Enfermedades de von Willebrand/sangre , Análisis Mutacional de ADN , Salud de la Familia , Secuencia de Aminoácidos

RESUMEN

Platelet-type von Willebrand disease (PT-VWD) and type 2B von Willebrand disease (2B-VWD) are rare bleeding disorders characterized by increased ristocetin-induced platelet aggregation (RIPA) at low concentrations of ristocetin. Diagnosis of either condition is not easy and the differential diagnosis between the two entities is especially challenging as evidenced by high levels of misdiagnosis of both conditions, but particularly PT-VWD. Five mutations in the GP1BA gene related to PT-VWD and less than 50 patients are currently reported worldwide. We herein describe a patient with severe bleeding symptoms, macrothrombocytopenia, mild spontaneous platelet aggregation, positive RIPA at 0.3 and 0.4 mg/mL, von Willebrand factor ristocetin cofactor (VWF:RCo) to antigen (VWF:Ag) < 0.2, normal VWF propeptide/VWF:Ag ratio, and RIPA mixing tests and cryoprecipitate challenge positive for PT-VWD. GP1BA gene was studied in the patient, in his mother, and in 100 healthy control subjects. We identified a heterozygous substitution G > T located at nucleotide 3805 in the g.DNA of the patient's GP1BA gene, resulting in a Trp to Leu amino acid change at residue 246 (p.W246L). This mutation was absent in his unaffected mother and also in the 100 controls, and was predicted as damaging by in silico analysis. The residue W246 is located within the VWF-binding region and exists in a strongly conserved position in the phylogenetic tree, which is expected to be unable to tolerate substitutions without changing its functional characteristics. These findings argue strongly in favor of the view that this substitution does not represent a polymorphism and is therefore responsible for the PT-VWD phenotype of the patient.

Asunto(s)

Predisposición Genética a la Enfermedad/genética , Mutación Missense , Complejo GPIb-IX de Glicoproteína Plaquetaria/genética , Enfermedades de von Willebrand/genética , Secuencia de Aminoácidos , Análisis Mutacional de ADN , Salud de la Familia , Femenino , Humanos , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Madres , Adulto Joven , Enfermedades de von Willebrand/sangre

RESUMEN

Clinical and laboratory data of children with von Willebrand disease (VWD) types have been derived from retrospective studies and small case series. This article reports on the clinical and laboratory data of a large pediatric cohort in one single Argentinian center. The biological and clinical responses to desmopressin and replacement therapies are also described. Over a 15-year period, 194 of 1150 children (16.9%) were diagnosed as having type 1 VWD (80%), type 2 VWD (19%), and type 3 VWD (1%). The distribution of the different type 2 VWD subtypes was type 2A VWD, 43%; type 2B VWD, 32%; type 2M VWD, 19%; and type 2N VWD, 6%. Eighty patients with type 1 VWD and 12 patients with type 2 VWD were prospectively evaluated to desmopressin (DDAVP) response. A complete response was observed in all children with type 1 VWD, whereas 40% of the children with severe type 1 VWD and with type 2 VWD achieved a complete response. All the children who received DDAVP as prophylaxis or treatment for bleeding had good clinical evolution. Considering the restricted availability of specialized hemostasis centers, we believe our clinical and laboratory approach appropriate for the detection of patients with different types of VWD. Further studies are necessary to determine epidemiological aspects of VWD in Argentina to estimate the necessary facilities and trained personnel for the diagnosis and management of patients with VWD.

Asunto(s)

Coagulantes/uso terapéutico , Enfermedades de von Willebrand/diagnóstico , Enfermedades de von Willebrand/tratamiento farmacológico , Adolescente , Argentina , Niño , Preescolar , Estudios de Cohortes , Desamino Arginina Vasopresina/uso terapéutico , Factor VIII/uso terapéutico , Femenino , Estudios de Seguimiento , Humanos , Lactante , Masculino , Mutación , Resultado del Tratamiento , Enfermedades de von Willebrand/genética , Factor de von Willebrand/genética , Factor de von Willebrand/uso terapéutico

RESUMEN

Von Willebrand disease (VWD) is a bleeding disorder with variable clinical expression. In this article we describe types, clinical features, genetic testing when needed, genotype/phenotype relationships, and the response to desmopressin (DDAVP) testing, according to our experience. Our findings are possible type 1, 69.6%; type 1, 13.5%; severe type 1, 0 .35%; type 3, 0.55%; type 2A, 9.5%; probable 2B, 0.6%; type 2M, 2.5%; and probable type 2N, 3.4%. The most frequent symptoms are ecchymoses-hematomas and epistaxis, and, in females >over 13 years also menorrhagia. In pregnant patients, assessment of laboratory parameters in months 7 and 8 is recommended to plan the need for prophylaxis at term. DDAVP merits to be considered as the first-choice therapy, including pregnant women and children, and no patient showed significant unwanted effects. Because this is a safe, effective, and affordable therapy, we hope to encourage clinicians, mainly pediatricians and obstetricians, to a wider use of DDAVP, especially in developing countries. We also report two patients with prophylactic treatment.

Asunto(s)

Desamino Arginina Vasopresina/uso terapéutico , Enfermedades de von Willebrand/diagnóstico , Enfermedades de von Willebrand/tratamiento farmacológico , Adolescente , Adulto , Argentina , Niño , Preescolar , Femenino , Estudios de Asociación Genética , Hemostáticos/uso terapéutico , Humanos , Masculino , Persona de Mediana Edad , Mutación , Embarazo , Resultado del Tratamiento , Adulto Joven , Enfermedades de von Willebrand/genética , Factor de von Willebrand/genética

RESUMEN

Type 2B von Willebrand disease (VWD2B) and platelet-type von Willebrand disease (PT-VWD) are rare bleeding disorders characterised by an increased ristocetin-induced platelet aggregation (RIPA) at low dose of ristocetin. It was the objective of this study to detect children with VWD2B and PT-VWD using RIPA at low dose of ristocetin (0.5 mg/ml) in the screening evaluation of bleeding disorders, and to analyse the phenotypic data along with the molecular findings. Over a 14-year period, 641 children with personal and family bleeding symptoms or bleeding from birth with previously uncharacterised haemostatic disorders were prospectively studied. Six unrelated patients (0.93%) showed RIPA at low dose of ristocetin. RIPA-based mixing studies identified that the plasma of the six probands and at least one parent from five unrelated families induced aggregation of normal platelets with the addition of low-dose ristocetin. None of the probands' platelets showed aggregation with cryoprecipitate. Low ristocetin cofactor activity/VWF antigen ratio with absent collagen binding activity or thrombocytopenia were detected respectively in only two patients. Molecular analysis of exon 28 of the VWF gene identified mutations in only three patients. No mutation in the GP1BA gene was found. In this large prospective paediatric study, the screening approach including RIPA at low dose of ristocetin permitted the detection of patients with VWD2B that would otherwise have been missed. No patient with phenotype or genotype of PT-VWD was identified. Heterogeneity of bleeding symptoms and phenotypic parameters were found among members of the same family.

Asunto(s)

Agregación Plaquetaria , Pruebas de Función Plaquetaria , Ristocetina , Enfermedad de von Willebrand Tipo 2/diagnóstico , Factor de von Willebrand/metabolismo , Adolescente , Argentina , Pruebas de Coagulación Sanguínea , Niño , Preescolar , Análisis Mutacional de ADN , Ensayo de Inmunoadsorción Enzimática , Femenino , Genotipo , Humanos , Lactante , Masculino , Mutación , Fenotipo , Agregación Plaquetaria/genética , Valor Predictivo de las Pruebas , Pronóstico , Estudios Prospectivos , Ristocetina/administración & dosificación , Enfermedad de von Willebrand Tipo 2/sangre , Enfermedad de von Willebrand Tipo 2/genética , Enfermedades de von Willebrand/sangre , Enfermedades de von Willebrand/diagnóstico , Enfermedades de von Willebrand/genética , Factor de von Willebrand/genética

RESUMEN

Von Willebrand disease (VWD) is one of the most common inherited bleeding diseases caused by a qualitative or quantitative deficiency of the von Willebrand factor (FvW). FvW is a multimeric glycoprotein synthesized by megakaryocytes and endothelial cells and it is present in the subendothelial matrix, blood plasma, platelets, and endothelium. This glycoprotein plays an important role in thrombus formation by initiating platelet adhesion to sites of injury as well as platelet aggregation. The aim of this study was to evaluate the activities of enzymes that hydrolyze adenine nucleotides in platelets, ristocetin-induced platelet aggregation (RIPA), and polymorphisms of the alpha2 gene of alpha2beta1 integrin from VWD patients. Platelet nucleoside triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase, and ecto-nucleotide pyrophosphatase/phosphodiesterase (E-NPP) activities were verified in 14 VWD patients. For RIPA determination, a final concentration of 1.25 mg/ml of ristocetin was used. Polymorphisms of the alpha2 gene were analyzed through PCR. Platelet NTPDase and E-NPP were decreased in VWD patients. 5'-Nucleotidase activity was not statistically significant between controls and VWD patients. RIPA was significantly reduced, with an allelic frequency of 78.57% for 807C in VWD patients. Our results indicated reduced platelet NTPDase and E-NPP activities which might be related to the low platelet adhesiveness. The prevalence of the 807C allele might account for the variability in bleeding in VWD.

Asunto(s)

Nucleótidos de Adenina/sangre , Plaquetas/enzimología , Hidrolasas/sangre , Integrina alfa2/genética , Integrina alfa2beta1/genética , Polimorfismo Genético , Enfermedades de von Willebrand/enzimología , Enfermedades de von Willebrand/genética , 5'-Nucleotidasa/sangre , Adolescente , Adulto , Brasil , Estudios de Casos y Controles , Niño , Femenino , Frecuencia de los Genes , Genotipo , Hemostasis/genética , Humanos , Hidrólisis , Masculino , Nucleósido-Trifosfatasa/sangre , Tiempo de Tromboplastina Parcial , Fenotipo , Hidrolasas Diéster Fosfóricas/sangre , Agregación Plaquetaria/genética , Recuento de Plaquetas , Tiempo de Protrombina , Pirofosfatasas/sangre , Adulto Joven , Enfermedades de von Willebrand/sangre

Asunto(s)

Humanos , Femenino , Embarazo , Calcio/análisis , Coagulación Intravascular Diseminada/patología , Enfermedades de von Willebrand/clasificación , Enfermedades de von Willebrand/genética , Enfermedades de von Willebrand/prevención & control , Hemorragia/etiología , Trastornos Hemostáticos/genética , Tromboplastina/análisis , Epistaxis/etiología , Hemodinámica , Menorragia/etiología , Fenotipo

RESUMEN

To investigate the origin of von Willebrand disease in Mexican Mestizo population, we analyzed exons 18, 19, 20, 28, 45, and 52 of the VWF gene from 34 Mexican Mestizo index cases, 28 of them affected but not related, using DNA amplification by polymerase chain reaction and direct sequencing. We found three novel mutations: E1447Q in one patient with type 1; P2781S in one patient with type 2M; and P812L in another type 1/2N patient. These mutations were not found in 100 normal alleles. Moreover, we found other mutations previously reported in the literature; one of them (G1609R) was the most frequent (6/28) in patients with VWD type 2A. This is the first molecular study in a Mexican group that has a particular mixture of Indigenous, Caucasian, and African genes.

Asunto(s)

Alelos , Exones , Mutación Missense , Enfermedades de von Willebrand/genética , Adolescente , Niño , Preescolar , Femenino , Humanos , Masculino , México , Factor de von Willebrand/genética

RESUMEN

Von Willebrand Factor (VWF) is a large multimeric glycoprotein expressed in the megakaryocytes and endothelial cells of all vertebrates. It participates fundamentally in the primary and secondary hemostasis because it induces the adhesion of platelets to vascular subendothelium and promotes aggregation of platelets when blood vessels and capillaries are damaged. In addition, VWF links to factor VIII which avoids its proteolysis. The deficiency or the inadequate synthesis of the VWF causes von Willebrand disease (VWD), which is the most common hereditary bleeding disorder in humans principally from mucous and cutaneous sites. VWD is difficult to detect with accuracy due to interrelation among VWF with different components of hemostasis, although it is performed by different tests of haemostatic system, and the basic mechanisms in VWD are herein emphasized. The diagnosis of VWD is difficult due to the heterogeneous manifestation of the disease, which also complicates its classification. This article focuses on the molecular aspects of the disease and discusses their possible clinical implications.

Asunto(s)

Enfermedades de von Willebrand/genética , Humanos , Biología Molecular , Enfermedades de von Willebrand/diagnóstico , Factor de von Willebrand/genética

Asunto(s)

Mutación/genética , Enfermedades de von Willebrand/genética , Adolescente , Adulto , Brasil/epidemiología , Niño , Preescolar , Femenino , Heterocigoto , Homocigoto , Humanos , Lactante , Masculino , Persona de Mediana Edad , Prevalencia , Enfermedades de von Willebrand/epidemiología

RESUMEN

The -1185A/G polymorphism in the 5'-regulatory region of the von Willebrand factor (VWF) gene was associated with VWF plasma levels in a normal population. This study was undertaken to evaluate whether there is a relationship between this polymorphism and type 1 von Willebrand disease (VWD), a disorder characterized by a quantitative deficiency of VWF. The association between this polymorphism and plasma VWF levels in normal Brazilian individuals was also analyzed. Control subjects (n = 460) and type 1 VWD patients (n = 41) were studied. Polymerase chain reaction (PCR) amplification of the 864-bp VWF promoter region followed by AccII restriction-digestion was used to identify the -1185A/G genotypes. The -1185G allele frequency was 57 percent in normal individuals and 63 percent in type 1 VWD patients, this difference was not significant (p = 0.29). No significant association was observed between -1185A/G genotypes and VWF plasma levels in normal individuals, although VWF levels were in the same direction as those reported by another study, with subjects carrying the G allele having the lower levels. These results suggest that -1185A/G polymorphism is not associated with the partial deficiency of VWF in type 1 VWD patients.

Asunto(s)

Humanos , Masculino , Femenino , Adulto , Enfermedades de von Willebrand/genética , Reacción en Cadena de la Polimerasa , Factor de von Willebrand , Variación Genética , Genotipo , Polimorfismo Genético , Factor de von Willebrand

RESUMEN

La enfermedad de von Willebrand (VWD) se caracteriza por manifestaciones hemorrágicas de tipo muco-cutáneo, causadas por una deficiencia cuali o cuantitativa del factor von Willebrand, responsable de la interacción de las plaquetas entre sí y con superficies subendoteliales a través de receptores específicos. Se diagnosticó VWD en 1885 individuos, encontrando una prevalencia de mujeres del 60,5 por ciento. La mayoría de los pacientes (71,1 por ciento) eran mayores de 13 años al momento de la consulta. El 91 por ciento de los pacientes fue tipo 1; 3,1 por ciento tipo 2 A; 2,7 por ciento tipo intraplaquetario bajo; 1,8 por ciento tipo 2N; 1,3 por ciento tipo severo y 0,1 por ciento fenotipo combinado 2N+1. Los síntomas clínicos más frecuentes fueron: equimosis-hematomas y epistaxis y, entre mujeres mayores de 13 años, menometrorragia. Se halló 6,7 por ciento de pacientes sin historia personal ni familiar de hemorragia, que consultaron por tener estudios preoperatorios anormales. Niveles normales de FVIII se hallaron en 37,8 por ciento de los pacientes. La prevalencia de grupo 0 entre nuestros pacientes fue del 70,5 por ciento, con disminución significativa sólo en los valores de VWF:Ag con respecto de los no-0. No hubo correlación entre el grupo 0 y la presencia de síntomas clínicos, cantidad de sitios de sangrado, sangrado gineco-obstétrico ni requerimientos transfusionales. De 81 individuos pertenecientes a 8 familias seleccionadas con 8 o más miembros estudiados (4 con miembros con VWD tipo 1 y 4 con tipo 2A) confirmamos que hay mayor número de miembros afectados en las familias con VWD tipo 2A, sugiriendo mayor penetrancia de VWD en este subgrupo. En el grupo de individuos no diagnosticados, la presencia de miembros sintomáticos fue más frecuente entre las familias con VWD tipo 1. (AU)

Asunto(s)

Humanos , Masculino , Adolescente , Adulto , Femenino , Factor de von Willebrand/genética , Factor de von Willebrand/ultraestructura , Enfermedades de von Willebrand/diagnóstico , Enfermedades de von Willebrand/fisiopatología , Enfermedades de von Willebrand/epidemiología , Enfermedades de von Willebrand/complicaciones , Enfermedades de von Willebrand/genética , Técnicas de Laboratorio Clínico , Signos y Síntomas