Search

Background: Patients with pathogenic variants in RASGRP2 (inherited platelet disorder (IPD)-18) exhibit normal platelet counts but impaired platelet aggregation and α IIb β 3 activation. Moderate-to-severe bleeding episodes require patients to be transfused with platelets and/or pro-hemostatic agents. We recently demonstrated that hemostatic efficacy of transfused platelets is limited by dysfunctional endogenous platelets in a mouse model of IPD-18 (Rasgrp2 -/- mice), as dysfunctional platelets were recruited to the forming hemostatic plug but did not participate in clot contraction. Thus, higher amounts of transfused platelets were required to outcompete these dysfunctional cells and to reverse bleeding., Objective: We here studied the usefulness of thromboelastography with platelet mapping (TEG-PM) for ex vivo monitoring of the hemostatic potential in Rasgrp2 -/- mice transfused with various amounts of wild-type (WT) platelets., Methods: Whole blood (WB) samples from WT and Rasgrp2 -/- mice were tested in TEG-PM and parameters for clot formation and contraction (K time, α-angle, maximum amplitude [MA]) were measured., Results: Rasgrp2 -/- WB samples did not contract in TEG-PM, consistent with a critical role of this protein in α IIb β 3 activation. Addition of WT platelets improved TEG parameters in a ratio-dependent manner, consistent with our recent in vivo studies showing impaired hemostasis at a 5:1, but not at a 2:1 ratio of mutant to WT platelets. K and α values were identified as better predictors of transfusion efficacy than MA, the most platelet-dependent TEG parameter., Conclusion: This proof-of-concept study supports the use of TEG-PM to monitor platelet transfusion ratios and hemostatic potential in IPD-18 and potentially other platelet disorders., Competing Interests: Declaration of competing interests There are no competing interests to disclose., (Copyright © 2024 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

The crucial role of platelets in hemostasis and their broad implications under various physiological conditions underscore the importance of accurate platelet-function testing. Platelets are key to clotting blood and healing wounds. Therefore, accurate diagnosis and management of platelet disorders are vital for patient care. This review outlines the significant advancements in platelet-function testing technologies, focusing on their working principles and the shift from traditional diagnostic methods to more innovative approaches. These improvements have deepened our understanding of platelet-related disorders and ushered in personalized treatment options. Despite challenges such as interpretation of complex data and the costs of new technologies, the potential for artificial-intelligence integration and the creation of wearable monitoring devices offers exciting future possibilities. This review underscores how these technological advances have enhanced the landscape of precision medicine and provided better diagnostic and treatment options for platelet-function disorders.

Germline mutations in RUNX1 result in rare autosomal-dominant familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML). As genetic analysis is becoming increasingly prevalent, the diagnosis rate of FPD/AML is expected to increase. In this report, we present two pedigrees, one diagnosed molecularly and another highly suspected to be FPD/AML, whose members both received allogeneic hematopoietic stem cell transplantation (HSCT). Both pedigrees had a family history of thrombocytopenia, platelet dysfunction, and hematological malignancies. One family inherited a frameshift mutation (p.P240fs) of RUNX1, a known pathogenic variant. Another family inherited a point mutation (p.G168R) in the runt-homology domain, the clinical significance of which is uncertain at this point. As this mutation was completely absent from all population databases and had a relatively high REVEL score of 0.947, we thought that it would be dangerous to ignore its possible pathogenicity. Consequently, we avoided choosing HSCT donors from relatives of both families and performed HSCT from unrelated donors. In conclusion, our experience with two families of FPD/AML highlights the importance of searching for gene mutations associated with germline predisposition and indicates the necessity of developing a donor coordination system for FPD/AML patients, as well as a support system for families., (© 2023. Japanese Society of Hematology.)

Platelets are key drivers of hemostasis. Low platelet counts, dysfunction in platelet adhesion, and aggregation lead to increased bleeding tendency. Inherited platelet disorders (IPDs) form a highly heterogeneous group of rare diseases with variable bleeding tendency. IPDs may be associated with other signs and symptoms often referred to as "syndromic." The underlying genetic defect may prone patients to develop hematopoietic diseases such as leukemia. Over the last decade, accumulating knowledge in genetics has led to the detection of many "new" platelet disorders. However, still many patients with a well-described platelet dysfunction remain undetected until severe bleeding occurs., Competing Interests: Disclosure The authors report no conflicts of interest in this work., (Thieme. All rights reserved.)

Inherited platelet disorders (IPDs) comprise a heterogeneous group of entities that manifest with variable bleeding tendencies. For successful treatment, the underlying platelet disorder, bleeding severity and location, age, and sex must be considered in the broader clinical context. Previous information from the AWMF S2K guideline #086-004 (www.awmf.org) is evaluated for validity and supplemented by information of new available and future treatment options and clinical scenarios that need specific measures. Special attention is given to the treatment of menorrhagia and risk management during pregnancy in women with IPDs. Established treatment options of IPDs include local hemostatic treatment, tranexamic acid, desmopressin, platelet concentrates, and recombinant activated factor VII. Hematopoietic stem cell therapy is a curative approach for selected patients. We also provide an outlook on promising new therapies. These include autologous hematopoietic stem cell gene therapy, artificial platelets and nanoparticles, and various other procoagulant treatments that are currently tested in clinical trials in the context of hemophilia., Competing Interests: The authors declare that they have no conflict of interest., (Thieme. All rights reserved.)

Background: Excessive or abnormal mucocutaneous bleeding (MCB) may impact all aspects of the physical and psychosocial wellbeing of those who live with it (PWMCB). The evidence base for the optimal diagnosis and management of disorders such as inherited platelet disorders, hereditary hemorrhagic telangiectasia (HHT), hypermobility spectrum disorders (HSD), Ehlers-Danlos syndromes (EDS), and von Willebrand disease (VWD) remains thin with enormous potential for targeted research., Research Design and Methods: National Hemophilia Foundation and American Thrombosis and Hemostasis Network initiated the development of a National Research Blueprint for Inherited Bleeding Disorders with extensive all-stakeholder consultations to identify the priorities of people with inherited bleeding disorders and those who care for them. They recruited multidisciplinary expert working groups (WG) to distill community-identified priorities into concrete research questions and score their feasibility, impact, and risk., Results: WG2 detailed 38 high priority research questions concerning the biology of MCB, VWD, inherited qualitative platelet function defects, HDS/EDS, HHT, bleeding disorder of unknown cause, novel therapeutics, and aging., Conclusions: Improving our understanding of the basic biology of MCB, large cohort longitudinal natural history studies, collaboration, and creative approaches to novel therapeutics will be important in maximizing the benefit of future research for the entire MCB community.

Background: Pre-injury anti-platelet use has been associated with increased risk of progression of traumatic intracranial hemorrhage (TICH) and worse outcomes. VerifyNow® assays assess platelet inhibition due to aspirin/clopidogrel. This study assesses the outcomes of patients with TICH and platelet dysfunction treated with desmopressin and/or platelets., Methods: We performed a retrospective chart review of patients with mild TICH at a level 1 trauma center 1/1/2013-6/1/2016. Patients with documented platelet dysfunction who received desmopressin and/or platelets were compared to those who were untreated. Primary outcomes were progression of TICH and neurologic outcomes at discharge., Results: Of 565 patients with a mild TICH, 200 patients had evidence of platelet dysfunction (a positive VerifyNow® assay). Patients had similar baseline demographics, injury characteristics, and rate of TICH progression; but patients who received desmopressin and/or platelets had worse Glasgow Outcomes Score at discharge., Conclusion: Treatment of patients with mild TICH and platelet dysfunction with desmopressin and/or platelets did not affect TICH progression but correlated with worse neurologic status at discharge., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Bleeding disorders due to platelet dysfunction are a common hematologic complication affecting patients, and typically present with mucocutaneous bleeding or hemorrhage. An inherited platelet disorder should be suspected in individuals with a suggestive family history and no identified secondary causes of bleeding. Genetic defects have been described at all levels of platelet activation, including receptor binding, signaling, granule release, cytoskeletal remodeling, and platelet hematopoiesis. Management of these disorders is typically supportive, with an emphasis on awareness, patient education, and anticipatory guidance to prevent future episodes of bleeding., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Purpose of Review: Megakaryocytes are rare hematopoietic cells that play an instrumental role in hemostasis, and other important biological processes such as immunity and wound healing. With the advent of cell reprogramming technologies and advances in differentiation protocols, it is now possible to obtain megakaryocytes from any pluripotent stem cell (PSC) via hematopoietic induction. Here, we review recent advances in PSC-derived megakaryocyte (iMK) technology, focusing on platform validation, disease modeling and current limitations., Recent Findings: A comprehensive study confirmed that iMK can recapitulate many transcriptional and functional aspects of megakaryocyte and platelet biology, including variables associated with complex genetic traits such as sex and race. These findings were corroborated by several pathological models in which iMKs revealed molecular mechanisms behind inherited platelet disorders and assessed the efficacy of novel pharmacological interventions. However, current differentiation protocols generate primarily embryonic iMK, limiting the clinical and translational potential of this system., Summary: iMK are strong candidates to model pathologic mutations involved in platelet defects and develop innovative therapeutic strategies. Future efforts on generating definitive hematopoietic progenitors would improve current platelet generation protocols and expand our capacity to model neonatal and adult megakaryocyte disorders., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Platelets play a major role in hemostasis as ppwell as in many other physiological and pathological processes. Accordingly, production of about 10 11 platelet per day as well as appropriate survival and functions are life essential events. Inherited platelet disorders (IPDs), affecting either platelet count or platelet functions, comprise a heterogenous group of about sixty rare diseases caused by molecular anomalies in many culprit genes. Their clinical relevance is highly variable according to the specific disease and even within the same type, ranging from almost negligible to life-threatening. Mucocutaneous bleeding diathesis (epistaxis, gum bleeding, purpura, menorrhagia), but also multisystemic disorders and/or malignancy comprise the clinical spectrum of IPDs. The early and accurate diagnosis of IPDs and a close patient medical follow-up is of great importance. A genotype-phenotype relationship in many IPDs makes a molecular diagnosis especially relevant to proper clinical management. Genetic diagnosis of IPDs has been greatly facilitated by the introduction of high throughput sequencing (HTS) techniques into mainstream investigation practice in these diseases. However, there are still unsolved ethical concerns on general genetic investigations. Patients should be informed and comprehend the potential implications of their genetic analysis. Unlike the progress in diagnosis, there have been no major advances in the clinical management of IPDs. Educational and preventive measures, few hemostatic drugs, platelet transfusions, thrombopoietin receptor agonists, and in life-threatening IPDs, allogeneic hematopoietic stem cell transplantation are therapeutic possibilities. Gene therapy may be a future option. Regular follow-up by a specialized hematology service with multidisciplinary support especially for syndromic IPDs is mandatory.

Purpose of Review: In this review, we discuss current clinical guidelines and potential underlying mechanisms regarding platelet transfusion therapy in patients at risk of bleeding, comparing management of patients with thrombocytopenia versus those with qualitative platelet disorders., Recent Findings: Platelet transfusion therapy is highly effective in managing bleeding in patients with hypoproliferative thrombocytopenia. Clinical trials have demonstrated that platelet transfusion can be used at a lower trigger threshold and reduced platelet doses, and may be used therapeutically rather than prophylactically in some situations, although additional data are needed. In patients with inherited platelet disorders such as Glanzmann's Thrombasthenia or those with RASGRP2 mutations, platelet transfusion may be ineffective because of competition between transfused and endogenous platelets at the site of vascular injury. Successful management of these patients may require transfusion of additional platelet units, or mechanism-driven combination therapy with other pro-hemostatic agents. In patients on antiplatelet therapy, timing of transfusion and inhibitor mechanism-of-action are key in determining therapeutic success., Summary: Expanding our understanding of the mechanisms by which transfused platelets exert their pro-hemostatic function in various bleeding disorders will improve the appropriate use of platelet transfusion.

Inherited platelet disorders are rare but they can have considerable clinical impacts, and studies of their causes have advanced understanding of platelet formation and function. Effective hemostasis requires adequate circulating numbers of functional platelets. Quantitative, qualitative and combined platelet disorders with a bleeding phenotype have been linked to defects in platelet cytoskeletal elements, cell surface receptors, signal transduction pathways, secretory granules and other aspects. Inherited platelet disorders have variable clinical presentations, and diagnosis and management is often challenging. Evaluation begins with detailed patient and family histories, including a bleeding score. The physical exam identifies potential syndromic features of inherited platelet disorders and rules out other causes. Laboratory investigations include a complete blood count, blood film, coagulation testing and Von Willebrand factor assessment. A suspected platelet function disorder is further assessed by platelet aggregation, flow cytometry, platelet dense granule release and/or content, and genetic testing. The management of platelet function disorders aims to minimize the risk of bleeding and achieve adequate hemostasis when needed. Although not universal, platelet transfusion remains a crucial component in the management of many inherited platelet disorders., Competing Interests: Disclosure of Conflicts of Interest The authors declare no competing conflicts of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

After vascular injury and exposure of subendothelial matrix proteins to the intravascular space, mediators of hemostasis are triggered and allow for clot formation and restoration of vascular integrity. Platelets are the mediators of primary hemostasis, creating a platelet plug and allowing for initial cessation of bleeding. Platelet disorders, qualitative and quantitative, may result in bleeding signs and symptoms, particularly mucocutaneous bleeding such as epistaxis, bruising, petechiae, and heavy menstrual bleeding. Increasing evidence suggests that platelets have functional capabilities beyond hemostasis, but this review focuses solely on platelet hemostatic properties. Herein, normal platelet function as well as the effects of abnormal function and thrombocytopenia are reviewed., (© American Academy of Pediatrics, 2020. All rights reserved.)

Background: Platelet dysfunction (PD) is an independent predictor of mortality in patients with severe traumatic brain injury (sTBI). Platelet transfusions (PLTs) have been shown to be an effective treatment strategy to reverse platelet inhibition. Their use is contingent on availability and may be associated with increased cost and transfusion-related complications, making desmopressin (DDAVP) attractive. We hypothesized that DDAVP would correct PD similarly to PLTs in patients with sTBI., Methods: This retrospective study evaluated all blunt trauma patients admitted to an urban, level 1 trauma center from July 2015 to October 2016 with sTBI (defined as head abbreviated injury scale [AIS] ≥3) and PD (defined as adenosine diphosphate [ADP] inhibition ≥60% on thromboelastography) and subsequently received treatment. Per our institutional practice, patients with sTBI and PD are transfused one unit of apheresis platelets to reverse inhibition. During a platelet shortage, we interchanged DDAVP for the initial treatment. Patients were classified as receiving DDAVP or PLT based on the initial treatment., Results: A total of 57 patients were included (DDAVP, n = 23; PLT, n = 34). Patients who received DDAVP were more severely injured (injury severity score, 29 vs. 23; p = 0.045), but there was no difference in head AIS (4 vs. 4, p = 0.16). There was no difference between the two groups in admission platelet count (244 ± 68 × 10/μL vs. 265 ± 66 × 10/μL, p = 0.24) or other coagulation parameters such as prothrombin time, partial thromboplastin time, or international normalized ratio. Before treatment, both groups had similar ADP inhibition as measured by thromboelastography (ADP, 86% vs. 89%, p = 0.34). After treatment, both the DDAVP and PLT groups had similar correction of platelet ADP inhibition (p = 0.28)., Conclusion: In patients with severe traumatic brain injury and PD, DDAVP may be an alternative to PLTs to correct PD., Level of Evidence: Therapeutic, level IV.

: Primary myelofibrosis (PMF) is a clonal hematopoietic stem cell disorder characterized by fibrosis of the marrow cavity, marked megakaryocyte atypia and progressive cytopenias. Although thrombosis predominates, bleeding is the primary manifestation in up to 20% of patients and may be life-threatening. In this report, we document restoration of megakaryocyte and platelet structure and function in PMF after allogeneic hematopoietic cell transplantation (HCT). A 59-year-old man presented with recurrent episodes of postoperative bleeding preceding a diagnosis of primary myelofibrosis (PMF). Platelet aggregation and secretion studies showed abnormal responses to all agonists tested (epinephrine, ADP, arachidonic acid, U46619, collagen, ristocetin) despite the presence of thrombocytosis. After an allogeneic HCT, platelet morphology and function studies were all normal. The pathophysiology of platelet dysfunction in myeloid neoplasia is not well understood but, as highlighted in our report, restoration of platelet function by HCT supports a clonal process involving an early hematopoietic progenitor cell.

The inherited platelet disorders are a heterogeneous group of disorders that can be pleotropic in their clinical presentations. They may present with variable platelet counts and bleeding, making their diagnosis difficult. New diagnostic tools range from flow cytometric platelet function assessments to next-generation sequencing. Several platelet disorders may now be treated with gene therapy or bone marrow transplant. Improved understanding of the molecular and biologic mechanisms of the inherited platelet disorders may lead to novel targeted therapies., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Light transmission aggregation (LTA) is the gold standard for the diagnosis of platelet function disorders (PFDs), but it is time-consuming and limited to specialized laboratories. Whole-blood impedance aggregometry (Multiplate) and platelet function analyzer (PFA) may be used as rapid screening tools to exclude PFDs. The aim of this study is to assess the diagnostic performance of Multiplate and PFA for PFDs, as detected by LTA.Data from preoperative patients, patients referred to the hematologist for bleeding evaluation, and patients with a diagnosed bleeding disorder were used. PFDs were defined as ≥2 abnormal LTA curves. Diagnostic performance of Multiplate and PFA for detecting PFDs was expressed as sensitivity and specificity. The ability of Multiplate agonists and PFA kits to detect corresponding LTA curve abnormalities was expressed as area under the receiver operating characteristic curve. Prevalence of PFDs was 16/335 (4.8%) in preoperative patients, 10/54 (18.5%) in referred patients, and 3/25 (12%) in patients with a diagnosed bleeding disorder. In preoperative and referred patients, the sensitivity of Multiplate and PFA for detecting mild PFDs varied between 0% and 40% and AUCs for detecting corresponding LTA curve abnormalities were close to 0.50. In patients with a diagnosed bleeding disorder, both assays could detect Glanzmann thrombasthenia (GT) with sensitivity of 100% and AUCs of 0.70-1.00. Multiplate and PFA cannot discriminate between preoperative and referred patients with and without mild PFDs, meaning that they cannot be used as screening tests to rule out mild PFDs in these populations. Both Multiplate and PFA can detect GT in previously diagnosed patients.

Mucocutaneous bleeding symptoms and/or persistent thrombocytopenia occur in individuals with congenital disorders of platelet function and number. Apart from bleeding, these disorders are often associated with additional hematologic and clinical manifestations, including auditory, immunologic, and oncologic disease. Autosomal recessive, dominant, and X-linked inheritance patterns have been demonstrated. Precise delineation of the molecular cause of the platelet disorder can aid the pediatrician in the detection and prevention of specific disorder-associated manifestations and guide appropriate treatment and anticipatory care for the patient and family., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Thrombocytopenia, defined as a platelet count less than 150 000 per microlitre, occurs in 7%-12% of all pregnancies. Apart from anaemia, it is the most common haematological disorder in pregnancy. Despite its frequent occurrence, thrombocytopenia often leads to difficulties of diagnosis and management in pregnancy. Typically, a pregnant woman will have platelet counts of 150 000 to 450 000 per microlitre and platelet counts may be slightly lower than those of healthy, non-pregnant controls. Approximately, 8% of pregnant women will develop mild thrombocytopenia (100 000-150 000 per microlitre) and while 65% of these women will have no underlying pathology, all pregnant women with platelet counts of less than 100 000 per microlitre should undergo further clinical and laboratory assessment. Thrombocytopenia in pregnancy occurs as a result of multiple distinct conditions, we present four cases of thrombocytopenia in pregnancy encountered in our unit over a 12-month period. These include gestational thrombocytopenia, immune thrombocytopenic purpura (ITP), thrombotic thrombocytopenic purpura (TTP) and thrombocytopenia absent radius (TAR) syndrome. The literature review of these cases highlights the significance of identification, understanding pathophysiology and a multidisciplinary approach to these conditions. We refresh knowledge on these conditions and emphasise the importance of thrombocytopenia in pregnancy., (© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Piperacillin-tazobactam is common empiric antibiotic therapy. Hematologic laboratory test abnormalities were documented but rare in premarketing studies, and whether these alterations are of clinical significance has been studied little. Very few cases of piperacillin-induced bleeding, thrombocytopenia, or both have been reported; aberrations in platelet function have not been implicated., Case Description: A 55-year old Vietnamese man with hypertension presented for treatment of an Intracranial hemorrhage. Platelet function assays (PFAs) at the time of external ventricular drain and quad-lumen bolt placement were normal, and imaging showed no hemorrhage after placement. The patient was later started on empiric piperacillin-tazobactam due to high suspicion for aspiration pneumonia. After removal of the quad-lumen bolt and external ventricular drain on separate days, both follow-up computed tomography scans showed new hematomas in the devices' tracts, with significant intraventricular hemorrhage. Repeat PFAs were abnormally prolonged, representing a distinct change from baseline. A trend toward normalization of PFAs was observed 6 hours after discontinuation of piperacillin-tazobactam with progression toward baseline thereafter., Conclusions: This is unique in that the significant bleeding that occurred was attributable to platelet dysfunction rather than thrombocytopenia. This is the first reported case of intracranial (periprocedural) hemorrhage potentially related to piperacillin-tazobactam; further research into this drug's impact upon qualitative platelet function is needed., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Thrombocytopenia or receipt of antiplatelet drugs, with or without bleeding, is a common indication for platelet transfusions in the ICU. However, there is almost no evidence base for these practices other than expert opinion. Also common is use of platelet transfusions prior to invasive procedures or surgery in patients with thrombocytopenia. Likewise, there is no high-quality evidence that such practices are efficacious or safe. Recently, it has become clear that, whether causal or not, patients receiving prophylactic platelet transfusions experience high rates of nosocomial infection, thrombosis, organ failure, and mortality, which increase the urgency and need for randomized trials to assess these practices. Investigational methods of improving the safety and efficacy of platelet transfusions include use of alternate strategies such as antifibrinolytics; use of ABO-identical, leukoreduced, and washed platelet transfusions; and improved storage solutions., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Invasive procedures in children are in most cases elective and are carried out in otherwise healthy children. While many surgeries are still performed in a hospital, more and more procedures are defined as "outpatient procedures," leading to increased discussion about safety and risks. This review will examine common practices, review the sparse literature and provide recommendations regarding the identification of children with increased bleeding risk, planning for children with known bleeding disorders and strategies for perioperative management. In conclusion, after careful planning, surgeries can be performed safely even in children with known bleeding disorders., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Myelofibrosis (MF) is a chronic myeloproliferative neoplasm characterized by bone marrow fibrosis, ineffective hematopoiesis, splenomegaly, constitutional symptoms, and shortened survival. Patients often experience multiple disease-associated, as well as treatment-emergent, cytopenias, including thrombocytopenia. However, patients with MF with thrombocytopenia have few therapeutic options, and there is little information on the management of these patients. Several Janus kinase (JAK) inhibitors have been developed for the treatment of MF, with one (ruxolitinib) having been approved. However, given their mechanism of action, JAK inhibitors are associated with high rates of thrombocytopenia. Patients can be successfully managed with dose modifications, but little is known about the safety and efficacy of these agents in patients with thrombocytopenia. Recent studies of JAK inhibitors in patients with MF who have low platelet counts have had mixed results. This review discusses the prevalence, prognostic implications, and management of thrombocytopenia in MF and the different therapeutic options available for this patient population, with an emphasis on current clinical experience with targeted therapies, as well as recent findings from several clinical studies currently underway.

Inherited disorders of platelet granules are clinically heterogeneous and their prevalence is underestimated because most patients do not undergo a complete diagnostic work-up. The lack of a genetic diagnosis limits the ability to tailor management, screen family members, aid with family planning, predict clinical progression and detect serious consequences, such as myelofibrosis, lung fibrosis and malignancy, in a timely manner. This is set to change with the introduction of high throughput sequencing (HTS) as a routine clinical diagnostic test. HTS diagnostic tests are now available, affordable and allow parallel screening of DNA samples for variants in all of the 80 known bleeding, thrombotic and platelet genes. Increased genetic diagnosis and curation of variants is, in turn, improving our understanding of the pathobiology and clinical course of inherited platelet disorders. Our understanding of the genetic causes of platelet granule disorders and the regulation of granule biogenesis is a work in progress and has been significantly enhanced by recent genomic discoveries from high-powered genome-wide association studies and genome sequencing projects. In the era of whole genome and epigenome sequencing, new strategies are required to integrate multiple sources of big data in the search for elusive, novel genes underlying granule disorders., (© 2016 John Wiley & Sons Ltd.)

Hemostasis is a complex and tightly regulated process whereby the body attempts to maintain a homeostatic balance to permit normal blood flow, without bleeding or thrombosis. When this balance is disrupted, due to trauma or underlying congenital bleeding or thrombotic disorders, clinical intervention may be required. To assist clinicians in diagnosing and managing affected patients, hemostasis laboratories offer an arsenal of tests, both routine (screening) and more specialized (diagnostic). In general, screening assays are used to screen for hemostasis-related disease or to monitor or measure the effect of anticoagulant therapy, which may be applied to treat patients with recent thrombosis or at risk of thrombosis. Diagnostic assays are used to diagnose or exclude specific hemostasis-related diseases, and in some cases, to monitor or measure the effect of anticoagulant therapy, or alternatively procoagulant therapy that may be applied to those at risk of bleeding. This chapter provides an overview of hemostasis and thrombosis with respect to laboratory tests that may be applied to affected patients.

Inherited platelet function disorders (IPFDs) make up a significant proportion of congenital bleeding diatheses, but they remain poorly understood and often difficult to diagnose. Therefore, a rational diagnostic approach, based on a standardized sequence of laboratory tests, with consecutive steps of increasing level of complexity, plays a crucial role in the diagnosis of most IPFDs. In this review we discuss a diagnostic approach through platelet phenotyping and genotyping and we give an overview of the options for the management of bleeding in these disorders and an account of the few systematic studies on the bleeding risk associated with invasive procedures and its treatment.

Thrombocytopenia is a frequent phenomenon in intensive care medicine. A variety of conditions can be responsible for low platelet counts. As platelets are part of the primary hemostatic system, bleeding is the most important complication of thrombocytopenia. Proper workup of the differential diagnosis to identify the cause of thrombocytopenia is essential because the various underlying disorders require different diagnostic and therapeutic management strategies. A low platelet count is a strong predictor of outcome in critically ill patients.This article summarizes the differential diagnosis and diagnostic workup of thrombocytopenia in the critically ill, describes the most important conditions, and gives an overview on therapeutic options and strategies.

The diagnosis of congenital and acquired bleeding disorders in infants requires an understanding of developmental haemostasis and the effect on laboratory testing. A systematic approach to bleeding in neonates will aid clinicians in the diagnosis and treatment, which may be caused by a wide variety of diseases. The clinical setting will help to direct the diagnostic pathway. This review will focus on the presentation and diagnosis of congenital and acquired bleeding disorders, including platelet disorders. Current research in this field is ongoing, including investigation into neonatal platelets and their different functionalities, platelet transfusion thresholds and how changes in coagulation factors may be linked to other homeostatic mechanisms., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Familial platelet disorder with propensity to acute myeloid leukemia (FPD/AML) is an autosomal dominant disease associated with a germline mutation in the RUNX1 gene and is characterized by thrombocytopenia and an increased risk of developing myeloid malignancies. We generated induced pluripotent stem cells (iPSCs) from dermal fibroblasts of a patient with FPD/AML possessing a nonsense mutation R174X in the RUNX1 gene. Consistent with the clinical characteristics of the disease, FPD iPSC-derived hematopoietic progenitor cells were significantly impaired in undergoing megakaryocytic differentiation and subsequent maturation, as determined by colony-forming cell assay and surface marker analysis. Notably, when we corrected the RUNX1 mutation using transcription activator-like effector nucleases in conjunction with a donor plasmid containing normal RUNX1 cDNA sequences, megakaryopoiesis and subsequent maturation were restored in FPD iPSC-derived hematopoietic cells. These findings clearly indicate that the RUNX1 mutation is robustly associated with thrombocytopenia in patients with FPD/AML, and transcription activator-like effector nuclease-mediated gene correction in iPSCs generated from patient-derived cells could provide a promising clinical application for treatment of the disease., (Copyright © 2015 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc. All rights reserved.)

This study evaluated 65 pregnancies in 34 women with five different inherited platelet function disorders. Gestation was similar to that of the general population. Severe bleeds requiring blood transfusions were observed in 50% of deliveries in Glanzmann thrombasthenia (GT), but not in the patients with delta storage pool disease, Hermansky-Pudlak syndrome, P2Y12 defect or defect of thromboxane A2 receptor. Of note, severe haemorrhage also occurred in women with GT who had received prophylactic platelet transfusions, suggesting that better preventive treatments are required. Diagnosis and degree of spontaneous bleeding tendency before pregnancy were reliable parameters to predict the delivery-related bleeding risk., (© 2015 John Wiley & Sons Ltd.)

We have proposed that modified platelets could potentially be used to correct intrinsic platelet defects as well as for targeted delivery of therapeutic molecules to sights of vascular injury. Ectopic expression of proteins within α-granules prior to platelet activation has been achieved for several proteins, including urokinase, factor (F) VIII, and partially for FIX. Potential uses of platelet-directed therapeutics will be discussed, focusing on targeted delivery of urokinase as a thromboprophylactic agent and FVIII for the treatment of hemophilia A patients with intractable inhibitors. This presentation will discuss new strategies that may be useful in the care of patients with vascular injury as well as remaining challenges and limitations of these approaches., (© 2015 International Society on Thrombosis and Haemostasis.)

Background: Both aspirin therapy and trauma impair platelet function. Platelet dysfunction is associated with worse outcomes in patients with traumatic intracranial hemorrhage (ICH). Platelet transfusion is often used to limit progression of ICH in patients on aspirin, but has not been shown to improve platelet function or outcomes. We hypothesized that platelet transfusion would improve aspirin-induced, but not trauma-induced, platelet dysfunction., Materials and Methods: In this prospective trial, blood samples were collected from patients evaluated in our level 1 trauma center with traumatic ICH, at the time of arrival and at the next clinical laboratory draw after admission. Patients on aspirin therapy were transfused one apheresis unit of platelets. Platelet function was assessed using a Multiplate multiple electrode aggregometer. Platelet activation was induced by collagen (COL) and arachidonic acid (AA). Agonist responses are reported as area under the aggregation curve in units (U). Reference ranges for agonist response were provided by the manufacturer, based on studies of healthy controls., Results: Seventeen patients with isolated ICH were enrolled, twelve taking aspirin and five not taking aspirin. All patients on aspirin received platelet transfusion. Median admission platelet function in patients taking aspirin was abnormal in response to both agonists. After transfusion, median platelet function in response to AA improved from 19.0 U to 26.0 U (P = 0.012), whereas there was no improvement in the COL response. In patients not on aspirin, platelet response to COL was abnormal at both time points., Conclusions: Patients with isolated ICH have trauma-induced platelet dysfunction. In addition, patients on aspirin have drug-induced abnormalities in platelet response to AA. Platelet transfusion improves aspirin-induced, but not trauma-induced, platelet dysfunction., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Platelet refractoriness (PR) due to HLA alloimmunization is a common and serious complication of patients receiving long-term packed red blood cell and platelet transfusions. Although most alloimmunized patients will respond to HLA-matched platelets, 20-50% of patients will remain refractory even to matched platelets. Several measures have been reported to overcome this complication, such as intravenous immunoglobulins (IVIG), plasma exchange (PE), protein A column therapy, or rituximab. We report a woman with acute myeloid leukemia secondary to myelodysplastic syndrome who was diagnosed with PR because of HLA alloimmunization. Due to difficulties in finding HLA-compatible platelet donors by cross-reactive groups in our panel of HLA-typed platelet donors, the patient received treatment with rituximab, PEs and IVIG. With this treatment strategy, the presence of HLA antibodies decreased from a panel-reactive antibody (PRA) of 89-0%. This allowed the performance of hematopoietic progenitor cell transplantation with random donor platelets. Rituximab, PE, and IVIG may be an option to overcome severe PR due to poly-specific HLA alloimmunization.

Familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML) is an autosomal dominant disease of the hematopoietic system that is caused by heterozygous mutations in RUNX1. FPD/AML patients have a bleeding disorder characterized by thrombocytopenia with reduced platelet numbers and functions, and a tendency to develop AML. No suitable animal models exist for FPD/AML, as Runx11/2 mice and zebra fish do not develop bleeding disorders or leukemia. Here we derived induced pluripotent stem cells (iPSCs) from 2 patients in a family with FPD/AML, and found that the FPD iPSCs display defects in megakaryocytic differentiation in vitro. We corrected the RUNX1 mutation in 1 FPD iPSC line through gene targeting, which led to normalization of megakaryopoiesis of the iPSCs in culture. Our results demonstrate successful in vitro modeling of FPD with patient-specific iPSCs and confirm that RUNX1 mutations are responsible for megakaryopoietic defects in FPD patients.

The diagnosis and management of bleeding disorders is made difficult by the complexity and variety of disorders, clinical symptoms and bleeding type and severity. von Willebrand disease (VWD) and platelet disorders are disorders of primary haemostasis and together represent the most common inherited bleeding disorders. In this article, we describe the diagnosis of VWD and platelet disorders and the treatment options for VWD., (© 2014 John Wiley & Sons Ltd.)

Inherited disorders of platelet function are a heterogeneous group. For optimal prevention and management of bleeding, classification and diagnosis of the underlying defect are highly recommended. An interdisciplinary guideline for a diagnostic approach has been published (AWMF # 086-003 S2K; Hämostaseologie 2014; 34: 201-212). Underlying platelet disorder, platelet count, age and clinical situation modify treatment. Exclusive transfusion of platelet concentrates may be inappropriate as potentially adverse effects can outweigh its benefit. A stepwise and individually adjusted approach for restitution and maintenance of haemostasis is recommended. Administration of antifibrinolytics is generally endorsed, but is of particular use in Quebec disease. Restricted to older children, desmopressin is favourable in storage pool disease and unclassified platelet disorders. Although licensed only for patients with Glanzmann thrombasthenia and alloantibodies, in clinical practice rFVIIa is widely used in inherited platelet disorders with severe bleeding tendency. This guideline aims at presenting the best available advice for the management of patients with inherited platelet function disorders.

Flow cytometry with its rapidly increasing applications is being used essentially in all fields of diagnostic medicine. In hematological disorders it is most commonly used in diagnosis, characterization, prognostication and even selecting target therapy of acute leukemia and to some extent lymphomas. It is increasingly finding place in other fields of hematology i.e., non-malignant disorders of all blood cell types including RBCs and platelets along with leukocytes. In this review the authors have discussed some of these applications with an emphasis on disorders specific to pediatric patients.

Platelets have an important role in the body because of their manifold functions in haemostasis, thrombosis, and inflammation. Platelets are produced by megakaryocytes (MKs) that are differentiated from haematopoietic stem cells via several consecutive stages, including MK lineage commitment, MK progenitor proliferation, MK differentiation and maturation, cell apoptosis, and platelet release. During differentiation, the cells migrate from the osteoblastic niche to the vascular niche in the bone marrow, which is accompanied by reactive oxygen species (ROS)-dependent oxidation state changes in the microenvironment, suggesting that ROS can distinctly influence platelet generation and function in a microenvironment-dependent manner. The objective of this review is to reveal the role of ROS in regulating MK proliferation, differentiation, maturation, and platelet activation, thereby providing new insight into the mechanism of platelet generation, which may lead to the development of new therapeutic agents for thrombocytopenia and/or thrombosis.

Inherited disorders of platelet function are characterized by highly variable mucocutaneous bleeding manifestations. The platelet dysfunction arises by diverse mechanisms, including abnormalities in platelet membrane glycoproteins, granules and their contents, platelet signaling and secretion mechanisms: thromboxane production pathways and in platelet procoagulant activities. Platelet aggregation and secretion studies using platelet-rich plasma currently form the primary basis for the diagnosis of an inherited platelet dysfunction. In most such patients, the molecular and genetic mechanisms are unknown. Management of these patients needs to be individualized; therapeutic options include platelet transfusions, 1-desamino-8d-arginine vasopressin (DDAVP), recombinant factor VIIa, and antifibrinolytic agents., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Platelet membrane glycoproteins play a key role in hemostasis and thrombosis. Although disorders of platelet membrane glycoproteins are rare, their effects on the lives of those affected are very important. Severe deficiencies manifest themselves early during childhood with mucocutaneous bleeding. Mild deficiencies may not be diagnosed until adulthood or until the hemostatic system is stressed by surgery or trauma. The diagnosis of these disorders requires detailed laboratory investigation. Management of bleeding in patients with inherited platelet disorders requires both preventive measures and the treatment of individual bleeding episodes according to severity. The study of platelet membrane disorders also has yielded important insights into the functions of affected proteins, information that has produced some of the most successful antithrombotic drugs currently in use., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Platelet transfusions are often a life-saving intervention, and the use of platelet transfusions has been increasing. Donor-derived platelet availability can be challenging. Compounding this concern are additional limitations of donor-derived platelets, including variability in product unit quality and quantity, limited shelf life and the risks of product bacterial contamination, other transfusion-transmitted infections, and immunologic reactions. Because of these issues, there has been an effort to develop strategies to generate platelets from exogenously generated precursor cells. If successful, such platelets have the potential to be a safer, more consistent platelet product, while reducing the necessity for human donations. Moreover, ex vivo-generated autologous platelets or precursors may be beneficial for patients who are refractory to allogeneic platelets. For patients with inherited platelet disorders, ex vivo-generated platelets offer the promise of a treatment via the generation of autologous gene-corrected platelets. Theoretically, ex vivo-generated platelets also offer targeted delivery of ectopic proteins to sites of vascular injury. This review summarizes the current, state-of-the-art methodologies in delivering a clinically relevant ex vivo-derived platelet product, and it discusses significant challenges that must be overcome for this approach to become a clinical reality.