Key Points Developed a targeted sequencing platform covering 63 genes linked to heritable bleeding, thrombotic, and platelet disorders. The ThromboGenomics platform provides a sensitive genetic test to obtain molecular diagnoses in patients with a suspected etiology.

Background Severe acute respiratory syndrome coronavirus 2 infection is associated with hypercoagulability, which predisposes to venous thromboembolism (VTE). We analyzed platelet and neutrophil activation in patients with coronavirus disease 2019 (COVID-19) and their association with VTE. Methods Hospitalized patients with COVID-19 and age- and sex-matched healthy controls were studied. Platelet and leukocyte activation, neutrophil extracellular traps (NETs), and matrix metalloproteinase 9, a neutrophil-released enzyme, were measured. Four patients were restudied after recovery. The activating effect of plasma from patients with COVID-19 on control platelets and leukocytes and the inhibiting activity of common antithrombotic agents on it were studied. Results A total of 36 patients with COVID-19 and 31 healthy controls were studied; VTE developed in 8 of 36 patients with COVID-19 (22.2%). Platelets and neutrophils were activated in patients with COVID-19. NET, but not platelet activation, biomarkers correlated with disease severity and were associated with thrombosis. Plasmatic matrix metalloproteinase 9 was significantly increased in patients with COVID-19. Platelet and neutrophil activation markers, but less so NETs, normalized after recovery. In vitro, plasma from patients with COVID-19 triggered platelet and neutrophil activation and NET formation, the latter blocked by therapeutic-dose low-molecular-weight heparin, but not by aspirin or dypiridamole. Conclusions Platelet and neutrophil activation are key features of patients with COVID-19. NET biomarkers may help to predict clinical worsening and VTE and may guide low-molecular-weight heparin treatment.

Summary. Background: Diagnosis of inherited platelet function disorders (IPFDs) is important for appropriate management and to improve epidemiologic and clinical knowledge. However, there remains a lack of consensus on the diagnostic approach. Objectives: To gain knowledge on the current practices for the diagnosis of IPFD worldwide. Methods: A 67-item questionnaire was distributed to the ISTH members and to the members of several national hemostasis and thrombosis societies. Results: A total of 202 laboratories from 37 countries participated in the survey. The most frequent criterion to define patients with a suspected IPFD was a history of mucocutaneous bleeding and no acquired cause, but heterogeneity on the identification criteria was evident. Only 64.5% of respondents performed a direct clinical interview. On average, each laboratory studied 72 patients per year. The most commonly used laboratory equipment were the lighttransmission aggregometer, the Platelet Function Analyzer-100, and the flow cytometer. Screening tests were platelet count, peripheral blood smear, light-transmission aggregometry, and Platelet Function Analyzer-100. Second-step tests were flow cytometry, molecular genetic analysis, and electron microscopy. Methodologies varied widely. In total,~14 000 patients were investigated yearly and 60% turned out to not have a defect. Of the remaining 40%, only 8.7% received a diagnosis at a molecular level. Conclusions: Many laboratories worldwide are involved in the diagnosis of IPFD. A large fraction of the patients studied remain without a diagnosis. A high variability in the diagnostic approaches is evident.

Megakaryocytes transfer a diverse and functional transcriptome to platelets during the final stages of thrombopoiesis. In platelets, these transcripts reflect the expression of their corresponding proteins and, in some cases, serve as a template for translation. It is not known, however, if megakaryocytes differentially sort mRNAs into platelets. Given their critical role in vascular remodeling and inflammation, we determined whether megakaryocytes selectively dispense transcripts for matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) into platelets. Next-generation sequencing (RNA-Seq) revealed that megakaryocytes express mRNA for 10 of the 24 human MMP family members. mRNA for all of these MMPs are present in platelets with the exception of MMP-2, 14, and 15. Megakaryocytes and platelets also express mRNA for TIMPs 1-3, but not TIMP-4. mRNA expression patterns predicted the presence and, in most cases, the abundance of each corresponding protein. Nonetheless, exceptions were observed: MMP-2 protein is present in platelets but not its transcript. In contrast, quiescent platelets express TIMP-2 mRNA but only traces of TIMP-2 protein. In response to activating signals, however, platelets synthesize significant amounts of TIMP-2 protein. These results demonstrate that megakaryocytes differentially express mRNAs for MMPs and TIMPs and selectively transfer a subset of these into platelets. Among the platelet messages, TIMP-2 serves as a template for signal-dependent translation. (Blood. 2011;118(7): 1903-1911) IntroductionThe biogenesis of platelets from megakaryocytes is a complex and intricate process that is incompletely understood. What is generally agreed on, however, is that platelets are assembled along intermediate pseudopodial-like extensions that derive from the cytoplasm of megakaryocytes. 1 These extensions are referred to as proplatelets. 1 Proplatelet formation has been modeled in vitro 2 and more recently observed in vivo. 3 Mechanisms that control proplatelet formation and platelet release are emerging, including the critical role of microtubules in driving the elongation of proplatelets. 4 Microtubules are also thought to be involved in sorting mitochondria as well as ␣ and dense granules into individual platelet buds. 5,6 Granules readily track along microtubular-rich shafts of proplatelets and distinct granule subpopulations are partitioned into platelets. 6 This suggests that platelet biogenesis is under discrete control.Protein synthesis also ramps up as proplatelets form. Adhesion molecules, secretome constituents, and other proteins are synthesized and packaged into discrete locations, including membranes and granules, so that platelets are loaded with requisite components before they are released into the bloodstream. 7 In addition to proteins, megakaryocytes send thousands of mRNAs and miRNAs into platelets. [8][9][10] The mRNAs are capped and polyadenylated on their 5Ј-and 3Ј-untranslated region (UTR), respectively, and code for protein when they are placed in in vitro tra...

Excessive bleeding at surgery is a feared complication in patients with inherited platelet disorders. However, very few studies have evaluated the frequency of surgical bleeding in these hemorrhagic disorders. We performed a worldwide, multicentric, retrospective study to assess the bleeding complications of surgery, the preventive and therapeutic approaches adopted, and their efficacy in patients with inherited platelet disorders: the Surgery in Platelet disorders And Therapeutic Approach (SPATA) study. We rated the outcome of 829 surgical procedures carried out in 423 patients with well-defined forms of inherited platelet disorders: 238 inherited platelet function disorders and 185 inherited platelet number disorders. Frequency of surgical bleeding was high in patients with inherited platelet disorders (19.7%), with a significantly higher bleeding incidence in inherited platelet function disorders (24.8%) than in inherited platelet number disorders (13.4%). The frequency of bleeding varied according to the type of inherited platelet disorder, with biallelic Bernard Soulier syndrome having the highest occurrence (44.4%). Frequency of bleeding was predicted by a pre-operative World Health Organization bleeding score of 2 or higher. Some types of surgery were associated with a higher bleeding incidence, like cardiovascular and urological surgery. The use of pre-operative pro-hemostatic treatments was associated with a lower bleeding frequency in patients with inherited platelet function disorders but not in inherited platelet number disorders. Desmopressin, alone or with antifibrinolytic agents, was the preventive treatment associated with the lowest bleedings. Platelet transfusions were used more frequently in patients at higher bleeding risk. Surgical bleeding risk in inherited platelet disorders is substantial, especially in inherited platelet function disorders, and bleeding history, type of disorder, type of surgery and female sex are associated with higher bleeding frequency. Prophylactic pre-operative pro-hemostatic treatments appear to be required and are associated with a lower bleeding incidence.

This is an open access article under the terms of the Creat ive Commo ns Attri bution-NonCo mmerc ial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Background Careful assessment of bleeding history is the first step in the evaluation of patients with mild/moderate bleeding disorders, and the use of a bleeding assessment tool (BAT) is strongly encouraged. Although a few studies have assessed the utility of the ISTH‐BAT in patients with inherited platelet function disorders (IPFD) none of them was sufficiently large to draw conclusions and/or included appropriate control groups. Objectives The aim of the present study was to test the utility of the ISTH‐BAT in a large cohort of patients with a well‐defined diagnosis of inherited platelets disorder in comparison with two parallel cohorts, one of patients with type‐1 von Willebrand disease (VWD‐1) and one of healthy controls (HC). Patients/Methods We enrolled 1098 subjects, 482 of whom had inherited platelet disorders (196 IPFD and 286 inherited platelet number disorders [IT]) from 17 countries. Results IPFD patients had significantly higher bleeding score (BS; median 9) than VWD‐1 patients (median 5), a higher number of hemorrhagic symptoms (4 versus 3), and higher percentage of patients with clinically relevant symptoms (score > 2). The ISTH‐BAT showed excellent discrimination power between IPFD and HC (0.9 < area under the curve [AUC] < 1), moderate (0.7 < AUC < 0.9) between IPFD and VWD‐1 and between IPFD and inherited thrombocytopenia (IT), while it was inaccurate (AUC ≤ 0.7) in discriminating IT from HC. Conclusions The ISTH‐BAT allows to efficiently discriminate IPFD from HC, while it has lower accuracy in distinguishing IPFD from VWD‐1. Therefore, the ISTH‐BAT appears useful for identifying subjects requiring laboratory evaluation for a suspected IPFD once VWD is preliminarily excluded.

Pregnancy in women with inherited thrombocytopenias is a major matter of concern as both the mothers and the newborns are potentially at risk of bleeding. However, medical management of this condition cannot be based on evidence because of the lack of consistent information in the literature. To advance knowledge on this matter, we performed a multicentric, retrospective study evaluating 339 pregnancies in 181 women with 13 different forms of inherited thrombocytopenia. Neither the degree of thrombocytopenia nor the severity of bleeding tendency worsened during pregnancy and the course of pregnancy did not differ from that of healthy subjects in terms of miscarriages, fetal bleeding and pre-term births. The degree of thrombocytopenia in the babies was similar to that in the mother. Only 7 of 156 affected newborns had delivery-related bleeding, but 2 of them died of cerebral hemorrhage. The frequency of delivery-related maternal bleeding ranged from 6.8% to 14.2% depending on the definition of abnormal blood loss, suggesting that the risk of abnormal blood loss was increased with respect to the general population. However, no mother died or had to undergo hysterectomy to arrest bleeding. The search for parameters predicting delivery-related bleeding in the mother suggested that hemorrhages requiring blood transfusion were more frequent in women with history of severe bleedings before pregnancy and with platelet count at delivery below 50 x 10 9 /L. ABSTRACT antepartum intracranial hemorrhage. On this basis, it has been concluded that bBSS is associated with a very high risk of serious bleeding in the mother and the neonate. Analysis of 339 pregnancies in 181 women with 13 different forms of inherited thrombocytopeniaSome information on pregnancy outcome is available also for MYH9-related disease (MYH9-RD), one of the most frequent forms of IT. A recent review of the literature examined 25 case reports and one case series describing a total of 75 pregnancies in 40 women.5 Postpartum hemorrhage in the mother occurred in 4 cases, while no obvious bleeding complications were reported among the newborns. Based on these data, MYH9-RD does not seem to increase bleeding risk either in mothers or neonates.Limited data on pregnancy outcomes have been provided for patients with mild to moderate thrombocytopenia due to monoallelic BSS (mBSS), in all cases induced by the p.Ala156Val substitution in GPIb alpha (Bolzano mutation). 6 Overall, 20 women delivered 34 children with no excessive maternal or neonatal bleeding. Although the authors did not provide information on management of pregnancies and childbirths, this study suggests that women with mBSS have gestational outcomes similar to healthy subjects.A moderate risk of bleeding during delivery has been reported in a series of subjects with thrombocytopenia induced by ANKRD26 mutations (ANKRD26-related thrombocytopenia, ANKRD26-RT).7 Thirteen patients gave birth, either vaginally or by caesarean section, with bleeding complications in 3 women. No information was provided o...