Eculizumab as first-line treatment for patients with severe presentation of complement factor H antibody-mediated hemolytic uremic syndrome.

BACKGROUND: Complement factor H (FH) antibody-mediated hemolytic uremic syndrome (HUS) has varying prevalence globally. Plasmapheresis and immunosuppressive drugs are the standard treatment. Recently, eculizumab has been reported as an effective alternative. This study aims to report four children with FH antibody-mediated HUS managed with eculizumab plus immunosuppression as first-line therapy. METHODS: A retrospective chart review was conducted for children aged ≤ 18 years old with complement-mediated HUS in two referral centers. Patients with FH antibody-mediated HUS treated with eculizumab as first-line therapy were included. RESULTS: Four children (aged 6-11 years old) were included. Dialysis was necessary in three patients. Eculizumab was administered 5-23 days after onset. None of them received plasmapheresis. Prednisone and mycophenolate mofetil were added after receiving positive FH antibody results. Hematological signs and kidney function improved after the second eculizumab dose. Eculizumab was discontinued in three patients after 6 months. One patient required rituximab due to persistent high FH antibody titers; discontinuation of eculizumab occurred after 15 months without recurrence. No treatment-related complications were observed. During a mean 12-month follow-up (range 6-24 months), no relapses were recorded and all patients ended with normal GFR. CONCLUSION: Our data suggest that a short course of 6 months of C5 inhibitor might be sufficient to reverse thrombotic microangiopathy symptoms and improve kidney function in patients with severe FH antibody-mediated HUS. Simultaneously, adding immunosuppressive agents might reduce the risk of relapse and allow cessation of C5 inhibition in a shorter period of time.

Clinical relevance of genetic variants in the von Willebrand factor according to in-silico methods.

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.

From the Discovery of ADAMTS13 to Current Understanding of Its Role in Health and Disease.

ADAMTS13 (a disintegrin-like metalloprotease domain with thrombospondin type 1 motif, member 13) is a protease of crucial importance in the regulation of the size of von Willebrand factor multimers. Very low ADAMTS13 activity levels result in thrombotic thrombocytopenic purpura, a rare and life-threatening disease. The mechanisms involved can either be acquired (immune-mediated thrombotic thrombocytopenic purpura [iTTP]) or congenital (cTTP, Upshaw-Schulman syndrome) caused by the autosomal recessive inheritance of disease-causing variants (DCVs) located along the ADAMTS13 gene, which is located in chromosome 9q34. Apart from its role in TTP, and as a regulator of microthrombosis, ADAMTS13 has begun to be identified as a prognostic and/or diagnostic marker of other diseases, such as those related to inflammatory processes, liver damage, metastasis of malignancies, sepsis, and different disorders related to angiogenesis. Since its first description almost 100 years ago, the improvement of laboratory tests and the description of novel DCVs along the ADAMTS13 gene have contributed to a better and faster diagnosis of patients under critical conditions. The ability of ADAMTS13 to dissolve platelet aggregates in vitro and its antithrombotic properties makes recombinant human ADAMTS13 treatment a potential therapeutic approach targeting not only patients with cTTP but also other medical conditions.

AISYF: first national, prospective, multicenter study of young patients with stroke in Argentina.

Up to 15% of all strokes affect young patients and the incidence of ischemic stroke in this population is rising. Nevertheless, there is limited information of cerebrovascular events in this population both in our country and in Latin America. The aim of our study was to evaluate the clinical characteristics and risk factors of young adults with stroke in Argentina. This is a prospective, multicenter study of stroke in young adults (18 - 55 years) in Argentina. Patients presenting with a cerebrovascular event within 180 days were included. Stroke subtypes were classified according to TOAST criteria. A total number of 311 patients were enrolled (men 53.9%, mean age: 43.3 years). Ischemic strokes occurred in 91.8% (brain infarcts 82.6%, transient ischemic attack 9.2%) and hemorrhagic strokes in 8.2%. The most frequent vascular risk factors (including ischemic and hemorrhagic strokes) were: hypertension 120 (41%), smoking 92 (31.4%), dyslipidemia 81 (27.6%) and, overweight/obesity: 74 (25.3%). Stroke subtypes were: large artery disease 12.3%, cardioembolism 7.5%, small artery occlusion 11.5%, other defined etiology 27.1%, and undetermined etiology 41.6%. Our study demonstrates that vascular risk factors are very frequent in young adults with stroke. Our findings underline that urgent strategies are required for primary and secondary stroke prevention in this group of patients.

Aproximadamente un 15% de todos los ataques cerebrovasculares afectan a pacientes jóvenes y su incidencia estaría en aumento. Existe escasa información sobre el ataque cerebral en esta población tanto en nuestro país como en Latinoamérica. El objetivo de nuestro estudio fue evaluar las características clínicas y los factores de riesgo de los adultos jóvenes con ictus en Argentina. Realizamos un estudio prospectivo y multicéntrico en adultos jóvenes (18-55 años) en Argentina, que presentaron un evento cerebrovascular dentro de los 180 días previos. Los subtipos de ictus se clasificaron según los criterios de TOAST. Se incluyeron un total de 311 pacientes (hombres 53.9%, edad media: 43,3 años). Los ataques cerebrovasculares isquémicos ocurrieron en el 91.8% (infartos cerebrales 82.6%, ataque isquémico transitorio 9.2%) y los eventos hemorrágicos correspondieron al 8.2%. Los factores de riesgo vascular más frecuentes (incluyendo los eventos isquémicos y hemorrágicos) fueron: hipertensión 120 (41%), tabaquismo 92 (31.4%), dislipidemia 81 (27.6%) y sobrepeso/obesidad: 74 (25.3%). Los subtipos de ictus isquémicos fueron: arteriopatía de gran vaso 12.3%, cardioembolismo 7.5%, oclusión de pequeña arteria 11.5%, otra etiología definida 27.1% y etiología indeterminada 41.6%. Los factores de riesgo vascular son muy frecuentes en los adultos jóvenes con ictus. Nuestros hallazgos subrayan que se requieren estrategias urgentes para la prevención primaria y secundaria del ictus en este grupo particular de pacientes en nuestro país.

AISYF: first national, prospective, multicenter study of young patients with stroke in Argentina / AISYF: primer estudio nacional, prospectivo y multicéntrico de pacientes jóvenes con ataque cerebral en Argentina

Abstract Up to 15% of all strokes affect young patients and the incidence of ischemic stroke in this population is rising. Nevertheless, there is limited information of cerebrovascular events in this population both in our country and in Latin America. The aim of our study was to evaluate the clinical characteristics and risk factors of young adults with stroke in Argentina. This is a prospective, multicenter study of stroke in young adults (18 - 55 years) in Argentina. Patients presenting with a cerebrovascular event within 180 days were included. Stroke subtypes were classified according to TOAST criteria. A total number of 311 patients were enrolled (men 53.9%, mean age: 43.3 years). Ischemic strokes occurred in 91.8% (brain infarcts 82.6%, transient ischemic attack 9.2%) and hemorrhagic strokes in 8.2%. The most frequent vascular risk factors (including ischemic and hemorrhagic strokes) were: hypertension 120 (41%), smoking 92 (31.4%), dyslipidemia 81 (27.6%) and, over weight/obesity: 74 (25.3%). Stroke subtypes were: large artery disease 12.3%, cardioembolism 7.5, small artery occlusion 11.5%, other defined etiology 27.1%, and undetermined etiology 41.6%. Our study demonstrates that vascular risk factors are very frequent in young adults with stroke. Our findings underline that urgent strategies are required for primary and secondary stroke prevention in this group of patients.

Resumen Aproximadamente un 15% de todos los ataques cerebrovasculares afectan a pacientes jóvenes y su incidencia estaría en aumento. Existe escasa información sobre el ataque cerebral en esta población tanto en nuestro país como en Latinoamérica. El objetivo de nuestro estudio fue evaluar las características clínicas y los factores de riesgo de los adultos jóvenes con ictus en Argentina. Realizamos un estudio prospectivo y multicéntrico en adultos jóvenes (18-55 años) en Argentina, que presentaron un evento cerebrovascular dentro de los 180 días previos. Los subtipos de ictus se clasificaron según los criterios de TOAST. Se incluyeron un total de 311 pacientes (hombres 53.9%, edad media: 43,3 años). Los ataques cerebrovasculares isquémicos ocurrieron en el 91.8% (infartos cerebrales 82.6%, ataque isquémico transitorio 9.2%) y los eventos hemorrágicos correspondieron al 8.2%. Los factores de riesgo vascular más frecuentes (incluyendo los eventos isquémicos y hemorrágicos) fueron: hipertensión 120 (41%), tabaquismo 92 (31.4%), dislipidemia 81 (27.6%) y sobrepeso/obesidad: 74 (25.3%). Los subtipos de ictus isquémicos fueron: arteriopatía de gran vaso 12.3%, cardioembolismo 7.5%, oclusión de pequeña arteria 11.5%, otra etiología definida 27.1% y etiología indeterminada 41.6%. Los factores de riesgo vascular son muy frecuentes en los adultos jóvenes con ictus. Nuestros hallazgos subrayan que se requieren estrategias urgentes para la prevención primaria y secundaria del ictus en este grupo particular de pacientes en nuestro país.

Type 2A and 2M von Willebrand Disease: Differences in Phenotypic Parameters According to the Affected Domain by Disease-Causing Variants and Assessment of Pathophysiological Mechanisms.

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.

Thrombotic microangiopathies: First report of 294 cases from a single institution experience in Argentina.

Introduction: Introduction: Thrombotic microangiopathies (TMAs) are rare disorders associated with fatal outcomes if left uncared for. However, healthcare problems in developing countries tend to limit medical assistance to patients. Methods: Methods: We prospectively studied an Argentine cohort of 294 consecutive patients from 2013 to 2016. Patients' subcategory classification relied on clinical symptoms and presence or absence of trigger events associated with TMA. Results: Main suspected disorders were the primary TMAs known as thrombotic thrombocytopenic purpura (TTP) (n = 72/294, 24%) and atypical haemolytic uraemic syndrome (aHUS) (n = 94/294, 32%). In acute phase, demographic parameters for acquired TTP (aTTP) (n = 28) and aHUS (n = 47) showed that both groups were characterised by a young median age (37 and 25 years, respectively) and female predominance (60% and 86%). Median of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 activity was significantly lower in aTTP than in aHUS group (1.4% vs 83%) and was associated with a more severe thrombocytopenia (15 × 109 vs 53 × 109/L). Creatinine (Cr) and urea (Ur) were significantly increased in aHUS compared to aTTP subjects (Cr: 3.7 vs 0.7 mg/dL, Ur: 118 vs 33 mg/dL). Gastrointestinal and neurological symptoms were more frequent in aHUS and aTTP, respectively. Conclusion: The first description of a TMA cohort in Argentina revealed similar clinical presentations to those of other countries.

[Argentine Consensus in effective management of anticoagulation clinics for the use of vitamin k antagonists]. / Consenso Argentino en gestión efectiva de clínicas de anticoagulación para el uso de antagonistas de la vitamina k.

Treating an anticoagulated patient with vitamin K antagonists (VKA) remains a challenge, especially in areas where dicoumarins are still the first drug of choice due to the cost of other oral anticoagulants. Anticoagulation clinics have proven to be the most efficient and safe way to avoid thrombotic and hemorrhagic complications and to keep patients in optimal treatment range. However, they require adequate infrastructure and trained personnel to work properly. In this Argentine consensus we propose a series of guidelines for the effective management of the anticoagulation clinics. The goal is to achieve the excellence in both the clinical healthcare and the hemostasis laboratory for the anticoagulated patient. The criteria developed in the document were agreed upon by a large group of expert specialists in hematology and biochemistry from all over the country. The criteria presented here must always be considered when indicating VKA although they had to be adapted to the unequal reality of each center. Taking these premises into consideration will allow us to optimize the management of the anticoagulated patient with VKA and thus minimize thrombotic and hemorrhagic intercurrences, in order to honor our promise not to harm the patient.

El tratamiento de un paciente anticoagulado con antagonistas de la vitamina K (AVK) sigue siendo un desafío, especialmente en regiones donde, por el costo, los dicumarínicos son todavía la alternativa más buscada a la hora de elegir un anticoagulante oral. Las clínicas de anticoagulación han demostrado ser la forma más eficiente y segura de evitar complicaciones trombóticas y hemorrágicas y de mantener al paciente en rango óptimo de tratamiento. Sin embargo, requieren de una adecuada infraestructura y personal capacitado para que funcionen eficientemente. En este consenso argentino se propone una serie de parámetros para la gestión efectiva de una clínica de anticoagulación. El objetivo es lograr una elevada calidad desde el punto de vista clínico-asistencial a través de un laboratorio de hemostasia de excelencia. Los criterios desarrollados en el documento fueron consensuados por un amplio grupo de expertos especialistas en hematología y en bioquímica de todo el país. Estos criterios deben adaptarse a la irregular disponibilidad de recursos de cada centro, pero siempre se los debe tener en cuenta a la hora de indicar el tratamiento anticoagulante con estas drogas. Tener en consideración estas premisas nos permitirá optimizar la atención del enfermo anticoagulado con AVK y de esta forma minimizar las intercurrencias trombóticas y hemorrágicas a las que está expuesto, para así honrar nuestra promesa de no dañar al paciente.

Consenso argentino en gestión efectiva de clínicas de anticoagulación para uso de antagonistas de la vitamina K / Argentine consensus in effective management of anticoagulation clinics for the use of vitamin K antagonists

Resumen El tratamiento de un paciente anticoagulado con antagonistas de la vitamina K (AVK) sigue siendo un desafío, especialmente en regiones donde, por el costo, los dicumarínicos son todavía la alternativa más buscada a la hora de elegir un anticoagulante oral. Las clínicas de anticoagulación han demostrado ser la forma más eficiente y segura de evitar complicaciones trombóticas y hemorrágicas y de mantener al paciente en rango óptimo de tratamiento. Sin embargo, requieren de una adecuada infraestructura y personal capacitado para que funcionen eficientemente. En este consenso argentino se propone una serie de parámetros para la gestión efectiva de una clínica de anticoagulación. El objetivo es lograr una elevada calidad desde el punto de vista clínico-asistencial a través de un laboratorio de hemostasia de excelencia. Los criterios desarrollados en el documento fueron consensuados por un amplio grupo de expertos especialistas en hematología y en bioquímica de todo el país. Estos criterios deben adaptarse a la irregular disponibilidad de recursos de cada centro, pero siempre se los debe tener en cuenta a la hora de indicar el tratamiento anticoagulante con estas drogas. Tener en consideración estas premisas nos permitirá optimizar la atención del enfermo anticoagulado con AVK y de esta forma minimizar las intercurrencias trombóticas y hemorrágicas a las que está expuesto, para así honrar nuestra promesa de no dañar al paciente.

Abstract Treating an anticoagulated patient with vitamin K antagonists (VKA) remains a challenge, especially in areas where dicoumarins are still the first drug of choice due to the cost of other oral anticoagulants. Anticoagulation clinics have proven to be the most efficient and safe way to avoid thrombotic and hemorrhagic complications and to keep patients in optimal treatment range. However, they require adequate infrastructure and trained personnel to work properly. In this Argentine consensus we propose a series of guidelines for the effective management of the anticoagulation clinics. The goal is to achieve the excellence in both the clinical healthcare and the hemostasis laboratory for the anticoagulated patient. The criteria developed in the document were agreed upon by a large group of expert specialists in hematology and biochemistry from all over the country. The criteria presented here must always be considered when indicating VKA although they had to be adapted to the unequal reality of each center. Taking these premises into consideration will allow us to optimize the management of the anticoagulated patient with VKA and thus minimize thrombotic and hemorrhagic intercurrences, in order to honor our promise not to harm the patient.

Biomarcadores y blancos moleculares del complemento en el diagnóstico de las microangiopatías trombóticas / Complement biomarkers and molecular targets in the diagnosis of thrombotic microangiopathies / Biomarcadores e alvos moleculares do complemento no diagnóstico das microangiopatias trombóticas

Resumen El sistema del complemento juega un papel central en la inmunidad innata, es una línea de defensa contra patógenos y participa en la homeostasis. La activación anormal del complemento contribuye al desarrollo de patologías de variable severidad, tanto inmunológicas y hematológicas como renales. Entre ellas, las microangiopatías trombóticas (MAT) representan un grupo de enfermedades raras con manifestaciones clínicas comunes caracterizadas por anemia hemolítica no inmune, trombocitopenia y daño de órgano(s) blanco. Si bien la clasificación de las MAT sigue siendo desafiante y no ha sido internacionalmente estandarizada, la descripción de entidades asociadas a anomalías del complemento fue comprobada con la eficiencia de la terapia anticomplemento en los pacientes. Las herramientas de diagnóstico desarrolladas en las últimas décadas son esenciales actualmente para diferenciar las MAT más características del grupo; esto es, la púrpura trombótica trombocitopénica (PTT) y el síndrome urémico hemolítico (SUH). En el presente trabajo se presenta una revisión del funcionamiento del sistema del complemento en condiciones fisiológicas, para poder explicar luego cuáles son las alteraciones del sistema implicadas en el desarrollo de las MAT y describir las herramientas disponibles para detectarlas en el laboratorio.

Abstract The complement system plays a crucial role in the innate immune response, being the first-line defense against pathogens and regulating homeostasis. Uncontrolled complement activation can cause immunologic, hematologic as well as renal syndromes of variable severity. Among them, thrombotic microangiopathies (TMA) represent a group of rare diseases characterised by similar clinical manifestations such as microangiopathic hemolytic anemia (MAHA), peripheral thrombocytopenia and organ injury. Although TMA classification is still challenging and no international consensus has been reached, complement-associated disorders have been described thanks to the efficiency of anti-complement therapy in patients. Diagnostic tools developed in the last decades are essential to differentiate the two most well characterized TMA: thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). This review will describe how the complement system works in physiological conditions in order to explain how complement abnormalities are involved in TMA, and finally how to detect those anomalies using laboratory tests.

Resumo O sistema do complemento desempenha um papel central na imunidade inata, sendo uma linha de defesa contra patógenos e participando da homeostase. A ativação anormal do complemento contribui para o desenvolvimento de patologias de gravidade variável, como imunológicas, hematológicas e renais. Entre elas, as microangiopatias trombóticas (MAT) representam um grupo de doenças raras com manifestações clínicas comuns caracterizadas por anemia hemolítica não imune, trombocitopenia e lesão de órgão(s) alvo. Embora a classificação das MAT continue sendo desafiadora e não tenha sido padronizada internacionalmente, a descrição de entidades associadas a anomalias do complemento foi comprovada com a eficiência da terapia anticomplemento nos pacientes. As ferramentas de diagnóstico desenvolvidas nas últimas décadas são atualmente essenciais para diferenciar as MAT mais características do grupo, que são a púrpura trombocitopênica trombótica (PTT) e a síndrome hemolítica urêmica atípica (SHU). Neste trabalho, é apresentada uma revisão do funcionamento do sistema de complemento em condições fisiológicas, a fim de explicar posteriormente quais são as alterações do sistema compreendidas no desenvolvimento das MAT, e descrever as ferramentas disponíveis para detectá-las em laboratório.

Administration of the vasopressin analog desmopressin for the management of bleeding in rectal cancer patients: results of a phase I/II trial.

Purpose The vasopressin analog desmopressin (dDAVP) is known to increase plasma levels of hemostatic factors, and preclinical studies in colorectal cancer models have demonstrated that it hampers tumor vascularization and metastatic progression. We evaluated safety and preliminary efficacy of dDAVP in rectal cancer patients with bleeding, before receiving specific oncologic treatment with surgery, chemotherapy and/or radiotherapy. Methods Patients with rectal cancer having moderate or severe rectal bleeding were enrolled in an open-label, dose-finding trial. Intravenous infusions of dDAVP were administered during two consecutive days in doses from 0.25 to 2.0 µg/kg, using single or twice daily regimen. Bleeding was graded using a score based on the Chutkan scale and tumor perfusion was evaluated by dynamic contrast-enhanced magnetic resonance imaging. Results The trial accrued a total of 32 patients. Dose-limiting toxicity occurred in patients receiving 1 µg/kg or higher. The most prominent treatment-related severe adverse event was hyponatremia. Most patients receiving the maximum tolerated dose of 0.5 µg/kg showed at least a partial hemostatic response and 58% developed a complete response with absence of bleeding at day 4 and/or at the last follow-up at day 14. Tumor perfusion was decreased in two-thirds of patients after dDAVP treatment. Conclusions dDAVP appeared as a promising hemostatic agent in rectal cancer patients with bleeding. Randomized clinical trials to confirm its effectiveness are warranted.Clinical trial registration www.clinicaltrials.gov NCT01623206.

Variantes genéticas frecuentes del factor von Willebrand: su influencia en el laboratorio y la clínica / Frequent genetic variants of von Willebrand factor: its influence in the laboratory and clinic

El factor von Willebrand (VWF) es una glucoproteína altamente polimórfica. Se describen aquí diferentes variantes genéticas asintomáticas altamente frecuentes, sus influencias sobre los estudios fenotípicos, en los niveles plasmáticos del mismo, y por consiguiente en diferentes entidades clínicas. Se detallan también variaciones en la frecuencia alélica según las etnias analizadas. El objetivo de este trabajo fue alertar sobre la necesidad de conocer la frecuencia de los polimorfismos en la población normal para evitar posibles conclusiones erróneas al momento del hallazgo de cambios no previamente reportados en la literatura científica.

The von Willebrand factor (VWF) is a highly polymorphic glycoprotein. Several frequent asymptomatic genetic variants, their influences on phenotypic studies, on the plasma levels of VWF, and therefore in different clinical entities are described here. Variations in allele frequency in different ethnic groups analyzed are also detailed. The aim of this study was to highlight the need to know the frequency of polymorphisms in the normal population to avoid possible erroneous conclusions at the time of finding genetic variants not previously reported in the scientific literature.

O fator von Willebrand (VWF) é uma glicoproteína altamente polimórfica. Diversas variantes genéticas assintomáticas muito frequentes são descritas aqui, suas influências em estudos fenotípicos, nos níveis plasmáticos de VWF e, portanto, em diferentes entidades clínicas. Variações na frequência alélica também são detalhadas segundo diferentes grupos étnicos analisados. O objetivo desse trabalho é alertar sobre a necessidade de conhecer a frequência dos polimorfismos na população normal, a fim de evitar possíveis conclusões errôneas no momento de encontrar variações genéticas não relatadas anteriormente na literatura científica.

Prevalence of Fabry Disease in Young Patients with Stroke in Argentina.

BACKGROUND: Fabry disease (FD) is an underdiagnosed cause of stroke in young adults, but the frequency of this association is largely unknown. We estimated the prevalence of FD in a nationwide cohort of young adults who had stroke and transient ischemic attack (TIA) in Argentina. METHODS: This was a prospective, multicenter study of stroke and FD in young adults (18-55 years) conducted in Argentina between 2011 and 2015. Patients were enrolled if they had had a TIA or an ischemic or hemorrhagic stroke within the previous 180 days. FD was diagnosed by measuring α-galactosidase A activity (males) and through genetic studies (females). RESULTS: We enrolled 311 patients (54% men, mean age: 41 years). Ischemic events occurred in 89% of patients (80% infarcts, 9% TIA) and hemorrhagic strokes in 11%. One female (.3% of the total group, 1% of the cryptogenic ischemic strokes) had the pathogenic mutation c.888G>A/p.Met296Ile /Exon 6 on the GAL gene. Her only other manifestation of FD was angiokeratoma. Eighteen females had nonpathogenic intronic variations: c.-10C>T, c.-12G>A, or both. Two patients had the nonpathogenic mutation D313Y, while a third had the likely benign mutation S126G. CONCLUSIONS: FD was identified in 1 patient (.3%) in this first Latin American study. The patient presented with a late-onset oligo-symptomatic form of the disease. A large number of nonpathogenic mutations were present in our cohort, and it is essential that they not be mistaken for pathogenic mutations to avoid unnecessary enzyme replacement treatment.

Marked bleeding diathesis in patients with platelet dysfunction due to a novel mutation in RASGRP2, encoding CalDAG-GEFI (p.Gly305Asp).

Congenital platelet function disorders are often the result of defects in critical signal transduction pathways required for platelet adhesion and clot formation. Mutations affecting RASGRP2, the gene encoding the Rap GTPase activator, CalDAG-GEFI, give rise to a novel, and rare, group of platelet signal transduction abnormalities. We here report platelet function studies for two brothers (P1 and P2) expressing a novel variant of RASGRP2, CalDAG-GEFI(p.Gly305Asp). P1 and P2 have a lifelong history of bleeding with severe epistaxis successfully treated with platelet transfusions or rFVIIa. Other bleedings include extended hemorrhage from minor wounds. Platelet counts and plasma coagulation were normal, as was αIIbß3 and GPIb expression on the platelet surface. Aggregation of patients' platelets was significantly impaired in response to select agonists including ADP, epinephrine, collagen, and calcium ionophore A23187. Integrin αIIbß3 activation and granule release were also impaired. CalDAG-GEFI protein expression was markedly reduced but not absent. Homology modeling places the Gly305Asp substitution at the GEF-Rap1 interface, suggesting that the mutant protein has very limited catalytic activity. In summary, we here describe a novel mutation in RASGRP2 that affects both expression and function of CalDAG-GEFI and that causes impaired platelet adhesive function and significant bleeding in humans.

Phenotypic Parameters in Genotypically Selected Type 2B von Willebrand Disease Patients: A Large, Single-Center Experience Including a New Novel Mutation.

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.

PT-VWD posing diagnostic and therapeutic challenges - small case series.

Despite the increased worldwide awareness, over the last decade, of the platelet-type von Willebrand Disease (PT-VWD), many uncertainties remain around this rare platelet bleeding disorder. This report aims to correctly identify and study the phenotype of new patients and highlights the diagnostic and therapeutic challenges this disease remains to pose. We describe four PT-VWD cases confirmed by genetic analysis in which either the diagnosis and/or the treatment posed challenge. We provide the details of the clinical presentation, laboratory analysis, and the treatment and the responses in each case. We show that in addition to type 2B VWD, PT-VWD can be misdiagnosed as idiopathic thrombocytopenic purpura, neonatal alloimmune thrombocytopenia, and unexplained gestational thrombocytopenia. The disease can be diagnosed as early as 1 year of age and with phenotypically normal parents. Bleeding in some patients can be managed successfully using Humate P and DDAVP combined with tranexamic acid with no significant thrombocytopenia. We provide for the first time an evidence of an efficient response to rFVIIa in PT-VWD. Anaphylactic reaction to VWF preparations may be related to PT-VWD and the development of HLA antibodies is not uncommon. Progressive thrombocytopenia with normal VWF levels can be seen with PT-VWD and the platelet count was normalized at 2.5 weeks postpartum in one case. We conclude that these studies represent a record of clinical observations/interventions that help improve diagnoses/management of PT-VWD, highlight the variations in age and clinical presentations, laboratory diagnostic approaches, the importance of genetic testing for accurate diagnosis and consideration of therapeutic alternatives.

Inhibidores adquiridos de la coagulación: enfoque diagnóstico y casos especiales / Acquired inhibitors of blood coagulation: diagnostic perpective and especial cases / Inibidores adquiridos da coagulação: abordagem diagnóstica e casos especiais

Los inhibidores adquiridos son defectos raros. Se asocian a diferentes manifestaciones clínicas con morbimortalidad significativa. Su detección es importante para implementar el tratamiento sin demora. Hay inhibidores específicos (bloquean función), contra todos los factores de la coagulación y además VWF, o de interferencia (afectan una o varias vías de la coagulación). Los inhibidores específicos son alo-anticuerpos desarrollados en pacientes deficitarios (complicación terapéutica) o auto-anticuerpos presentes en individuos sin alteraciones previas. Hay anticuerpos específicos que pueden afectar la depuración pero no inhiben función. Inhibidores de interferencia: inmunoglobulinas u otras sustancias (heparina/heparinoides, PDF/pdf, PIVKAS, moléculas anómalas, etc.) asociadas a diferentes situaciones clínicas (asintomáticos, sangrados, trombosis y/o complicaciones obstétricas). El laboratorio es fundamental para el diagnóstico. Las pruebas globales detectan el defecto, que no corrigen por el agregado de plasma normal; se caracteriza luego el tipo de inhibidor y eventualmente se titula. Esto es complejo; hay variabilidad en los resultados y posibilidad de falsos positivos o negativos, además las pruebas no son estrictamente específicas. Los algoritmos diagnósticos son útiles, pero no contemplan la posibilidad de defectos combinados. Es crítico caracterizar al inhibidor y descartar posibles interferencias o defectos concomitantes; ello requiere aplicar las pruebas adecuadas e interpretarlas correctamente.

Acquired inhibitors are rare disorders. They are associated with different clinical behaviours and significant morbi-mortality. Detection is important in order to start treatment urgently. There are either specific inhibitors, which block function, against all coagulation factors, and VWF, or with interference effects, on one or more coagulation pathways. Specific inhibitors are either allo-antibodies developed in deficient patients, which give rise to therapeutic complication; or auto-antibodies, which are present in individuals without previous defects. There are specific antibodies that can affect clearance but which cannot block the function. Inhibitors with interference effects are immunoglobulins or other substances (heparin/heparinoids, FDP/fdp, PIVKAS, abnormal molecules, etc.) associated with different clinical settings (asymptomatic, bleeding, thrombosis and/or obstetric complications). Laboratory results are fundamental for the diagnosis. Global tests are able to detect the defect, which is not corrected by the addition of normal plasma; the type of inhibitor is then characterized and titration of the inhibitor is eventually performed. This is complex; there is variability in the results and there is likelihood of false positive or negative results; moreover, the tests are not strictly specific. Diagnostic algorithms are useful tools but they do not consider combined defects. It is a critical point to characterize the inhibitor and exclude possible interferences or concomitant defects; this demands application of the correct tests without misinterpretations.

Os inibidores adquiridos são defeitos raros. Associam-se a diferentes manifestações clínicas com morbimortalidade significativa. Sua detecção é importante para implementar o tratamento sem demora. Há inibidores específicos (bloqueiam função), contra todos os fatores da coagulação e também VWF, ou de interferência (afetam uma ou várias vias da coagulação). Inibidores específicos: - aloanticorpos desenvolvidos em pacientes deficitários (complicação terapêutica); - autoanticorpos, em indivíduos sem alterações prévias. Existem anticorpos específicos que podem afetar a depuração, mas não inibem função. Inibidores de interferência: imunoglobulinas ou outras substâncias (heparina/heparinoides, PDF/pdf, PIVKAS, moléculas anômalas, etc.) associadas a diferentes situações clínicas (assintomáticos, sangramentos, tromboses e/ou complicações obstétricas). O laboratório é fundamental para o diagnóstico. Os testes globais detectam o defeito, que não corrige pelo acréscimo de plasma normal; caracteriza-se depois o tipo de inibidor e eventualmente é titulado. Isto é complexo; há variabilidade nos resultados e possibilidade de falsos positivos ou negativos, além disso os testes não são rigorosamente específicos. Os algoritmos diagnósticos são úteis, mas não consideram a possibilidade de defeitos combinados. É crítico caracterizar o inibidor e descartar possíveis interferências ou defeitos concomitantes; isso requer aplicar os testes adequados e interpretá-los corretamente.

Factor von Willebrand y Enfermedad de von Willebrand: nuevos enfoques diagnósticos / Von Willebrand Factor and von Willebrand disease: new approaches to diagnosis / Fator Von Willebrand e doença de von Willebrand: novas abordagens diagnósticas

El factor von Willebrand (VWF) es una glicoproteína que se sintetiza en células endoteliales y en megacariocitos. Su vida media es de ~12 horas. Está formado por multímeros de diferentes pesos moleculares, pequeños, intermedios, grandes y extragrandes. La actividad funcional reside en los multímeros grandes, y los extragrandes son trombogénicos. Promueve la adhesión plaquetaria al subendotelio, la agregación plaquetaria y transporta al FVIII en plasma, protegiéndolo de su degradación por proteasas. La enfermedad de von Willebrand es el trastorno hemorrágico más frecuente; se describen deficiencias cuantitativas (parcial: VWD1; total: VWD3) o defectos cualitativos (VWD2A, VWD2M, VWD2B y VWD2N). La expresión clínica es variable (sangrado muco-cutáneo) y su herencia autosómica, dominante o recesiva, según las variantes. Los niveles del VWF dependen de factores genéticos y no genéticos que afectan el diagnóstico y la expresión clínica. Para llegar al diagnóstico se precisan varias pruebas, algunas inespecíficas. El laboratorio comienza con pruebas orientadoras, se continúa con pruebas confirmatorias, y posteriormente pruebas para definir la variante de VWD. El diagnóstico genotípico es fundamental para lograr el diagnóstico diferencial entre VWD2B vs. PT-VWD y VWD2N vs. Hemofilia A (leve-moderada), diferenciar VWD de AVWS y discriminar variantes VWD2.

Von Willebrand factor (VWF) is a glycoprotein with essential roles in both primary and secondary hemostasis, synthesized by endothelial cells and megakaryocytes. Its half-life is ~12 hours. VWF consists in multimers of different molecular weight: small, intermediate, large and ultra large. The functional activity resides in the large multimers; the ultra large are thrombogenic. VWF promotes platelet adhesion to subendothelium, platelet aggregation and binds FVIII, protecting it from proteolysis and preserving its hemostatic function. Von Willebrand disease is the most common bleeding disorder; qualitative defects (VWD2A, VWD2M, VWD2B and VWD2N) and quantitative deficiencies (VWD1 and VWD3) are described. The clinical expression is variable (mucocutaneous bleeding); VWF levels depend on genetic and non-genetic factors affecting diagnosis and clinical expression. The inheritance can be autosomal, dominant or recessive according to the variants. To reach diagnosis, several tests are required, being some of them unspecific. The laboratory testing begins with global tests, followed by confirmatory tests and further tests to define the variant of VWD. Genotypic studies are essential to achieve the differential diagnosis between VWD2B vs. PT-VWD, VWD2N vs. Hemophilia A (mild to moderate) and differentiate VWD from AVWS and discriminate VWD2 variants.

O fator de von Willebrand (vWF) é uma glicoproteína sintetizada em células endoteliais e em megacariócitos. Sua vida média é de ~12 horas. É constituído por multímeros de pesos moleculares diferentes, pequenos, intermediários, grandes e extragrandes. A atividade funcional reside nos multímeros grandes, sendo os extragrandes, trombogênicos. Promove adesão das plaquetas ao subendotélio, a agregação plaquetária e transporta o FVIII em plasma, protegendo-o de sua degradação. A doença de von Willebrand é o distúrbio hemorrágico mais frequente; são descritas deficiências quantitativas (parcial: VWD1; total: VWD3) ou defeitos qualitativos (VWD2A, VWD2M, VWD2B e VWD2N). A expressão clínica é variável, (sangramento mucocutâneo), e sua herança autossômica dominante ou recessiva de acordo com as variantes. Os níveis de vWF dependem de fatores genéticos e não-genéticos que afetam o diagnóstico e a expressão clínica. Para fazer o diagnóstico, vários testes são necessários, alguns inespecíficos. O laboratório começa com testes orientadores, continua com testes de confirmação e, mais tarde, com testes para definir a variante de VWD. O diagnóstico genotípico é essencial para alcançar o diagnóstico diferencial entre VWD2B vs. PT-VWD e VWD2N vs. Hemofilia A (leve a moderada), diferenciar VWD de AVWS, discriminar variantes VWD2.