Glanzmann thrombasthenia

Relationship between LDL-cholesterol, small and dense LDL particles, and mRNA expression in a cohort of African Americans

Understanding the characteristics and behavior of low-density lipoprotein (LDL) particles provides insights into the atherogenic risk of elevated LDL cholesterol in hypercholesterolemia, cardiovascular disease risks. Studying LDL particles helps identify specific LDL subtypes [e.g., small dense LDL particles (sdLDL)] that may be atherogenic and, consequently, potential targets for therapeutics. This study cohort consists of African Americans (AAs), a population disproportionately affected by cardiovascular diseases, thereby accentuating the importance of the investigation. Differential expression (DE) analysis was undertaken using a dataset comprising 17,947 protein-coding mRNAs from the whole blood transcriptomes of 416 samples to identify mRNAs associated with low-density lipoprotein cholesterol (LDL-C) and sdLDL plasma levels. Subsequently, mediation analyses were used to investigate the mediating role of sdLDL particles on the relationship between LDL-C levels and mRNA expression. Finally, pathway enrichment analysis was conducted to identify pathways involving mRNAs whose relationship with LDL-C is mediated by sdLDL. DE analysis revealed 1,048 and 284 mRNA transcripts differentially expressed by LDL-C and sdLDL levels, respectively. Mediation analysis revealed that the associations between LDL-C and 33 mRNAs were mediated by sdLDL. Of the 33 mRNAs mediated by sdLDL, 18 were mediated in both males and females. Nine mRNAs were mediated only in females, and six were mediated only in males. Pathway analysis showed that 33 mRNAs are involved in pathways associated with the immune system, inflammatory response, metabolism, and cardiovascular disease (CVD) risk. In conclusion, our study provides valuable insights into the complex interplay between LDL-C, sdLDL, and mRNA expression in a large sample of AAs. The results underscore the importance of incorporating sdLDL measurement alongside LDL-C levels to improve the accuracy of managing hypercholesterolemia and effectively stratify the risk of CVD. This is essential as differences in sdLDL modulate atherogenic properties at the transcriptome level.NEW & NOTEWORTHY The study investigated the interplay between LDL-C and mRNA expression, focusing on the role of small dense LDL (sdLDL) particles and sex differences. Differential expression analysis identified 1,048 and 284 mRNAs associated with LDL-C and sdLDL levels, respectively. Mediation analysis revealed that sdLDL mediates the relationship between LDL-C and 33 mRNAs involved in immune, inflammatory, and metabolic pathways. These findings highlight the significance of sdLDL in cardiovascular disease risk assessment and underscore sex-specific differences in lipid metabolism.

Current status and future prospects of activated recombinant coagulation factor VIIa, NovoSeven®, in the treatment of haemophilia and rare bleeding disorders

rFVIIa, a human recombinant activated coagulation factor VII, has been used worldwide for more than two decades for the treatment of bleeding episodes and prevention of bleeding in patients undergoing surgery/invasive procedures with congenital haemophilia A or B with inhibitors (CHwI A or B), acquired haemophilia (AH), congenital factor VII deficiency and Glanzmann thrombasthenia (GT), refractory to platelet transfusion. The approved dosage, administration and indication of rFVIIa in the US, Europe and Japan differ, depending on the needs of the patient population and regulatory practices. This review presents an overview of the current status and future prospects, including that from a Japanese perspective, of using rFVIIa in the treatment of approved indications. The efficacy and safety of rFVIIa in the approved indications has been demonstrated in several randomised and observational studies and data from registries. The overall incidence of thrombosis across all approved indications in a retrospective safety assessment of clinical trials and registries, prelicensure studies and postmarketing surveillance studies of rFVIIa use was 0.17%. Specifically, the risk of thrombotic events was 0.11% for CHwI, 1.77% for AH, 0.82% for congenital factor VII deficiency and 0.19% for GT. Emerging non-factor therapies such as emicizumab have changed the treatment landscape of haemophilia A, including preventing bleeding in patients with CHwI. However, rFVIIa will continue to play a significant role in the treatment of such patients, particularly during breakthrough bleeding or surgical procedures.

Glanzmann's thrombasthenia: A nightmare for hernia surgeons

ABSTRACT

Glanzmann's thrombasthenia is a rare inherited disorder affecting one in one million. It is characterised by a lack of platelet aggregation due to a defect in the platelet membrane receptor complex (αIIb/βIIIa), which mediates the aggregation of platelets at the site of vessel injury. We report here the first case of successful perioperative haemostatic management of a male patient with Glanzmann's thrombasthenia, who underwent an elective laparoscopic hernia repair. The patient was posted for elective surgery considering the availability of expertise in minimally invasive surgery and accessibility to recombinant activated factor VII. The patient was operated using the extended-view totally extraperitoneal technique for inguinal hernia repair. The patient recovered successfully and reported no complication during follow-up. We conclude that with proper perioperative haematological consultation, and careful coordination between anaesthetists and surgeons, elective laparoscopic procedure can be done in patients with Glanzmann's thrombasthenia, with only recombinant factor VIIa support.

Catheter Intervention in a Patient with Intracranial Aneurysms and Glanzmann Thrombasthenia Caused by a Novel Homozygous Likely Pathogenic Variant in the ITGA2B Gene

Glanzmann Thrombasthenia (GT) is an inherited platelet disorder caused by defects in platelet integrin αIIbβ3 (GPIIb/IIIa), which is a platelet receptor essential for the binding of fibrinogen. This can lead to severe bleeding, especially after trauma or perioperatively, and to microcytic anemia because of chronic blood loss. We report on a 40-year-old female patient with extensive bleeding complications and platelet antibody formation who presented in Homburg and Freiburg for extensive platelet function analyses and molecular genetic analyses. According to platelet aggregometry, the patient had previously been diagnosed with Glanzmann Thrombasthenia (GT). In addition, an MRI scan had been performed due to an unsteady gait and had revealed bilateral para-ophthalmic aneurysms of both internal carotid arteries (ICAs). Assuming a 5% rupture risk per 5 years for each aneurysm, the patient was offered and accepted endovascular treatment. Next-generation sequencing (NGS) panel analysis identified a previously undescribed homozygous one-base-pair deletion in ITGA2B, which leads to a loss of function of the αIIb-subunit of the receptor. This case illustrates the difficulties that can arise regarding the treatment of patients with rare platelet bleeding disorders, and supports the importance of continuous medical care by a specialized hemophilia center for these patients.

Megakaryocyte-induced contraction of plasma clots: cellular mechanisms and structural mechanobiology

ABSTRACT

Nonmuscle cell contractility is an essential feature underlying diverse cellular processes such as motility, morphogenesis, division and genome replication, intracellular transport, and secretion. Blood clot contraction is a well-studied process driven by contracting platelets. Megakaryocytes (MKs), which are the precursors to platelets, can be found in bone marrow and lungs. Although they express many of the same proteins and structures found in platelets, little is known about their ability to engage with extracellular proteins such as fibrin and contract. Here, we have measured the ability of MKs to compress plasma clots. Megakaryocytes derived from human induced pluripotent stem cells (iPSCs) were suspended in human platelet-free blood plasma and stimulated with thrombin. Using real-time macroscale optical tracking, confocal microscopy, and biomechanical measurements, we found that activated iPSC-derived MKs (iMKs) caused macroscopic volumetric clot shrinkage, as well as densification and stiffening of the fibrin network via fibrin-attached plasma membrane protrusions undergoing extension-retraction cycles that cause shortening and bending of fibrin fibers. Contraction induced by iMKs involved 2 kinetic phases with distinct rates and durations. It was suppressed by inhibitors of nonmuscle myosin IIA, actin polymerization, and integrin αIIbβ3-fibrin interactions, indicating that the molecular mechanisms of iMK contractility were similar or identical to those in activated platelets. Our findings provide new insights into MK biomechanics and suggest that iMKs can be used as a model system to study platelet contractility. Physiologically, the ability of MKs to contract plasma clots may play a role in the mechanical remodeling of intravascular blood clots and thrombi.

In vitro characterization of rare anti-αIIbβ3 isoantibodies produced by patients with Glanzmann thrombasthenia that severely block fibrinogen binding and generate procoagulant platelets via complement activation

Background

Glanzmann thrombasthenia (GT) is a rare bleeding disorder caused by inherited defects of the platelet αIIbβ3 integrin. Platelet transfusions can be followed by an immune response that can block integrin function by interfering with fibrinogen binding.

Objectives

In this study, we aimed to determine the prevalence of such isoantibodies and better characterize their pathogenic properties.

Methods

Twelve patients with GT were evaluated for anti-αIIbβ3 isoantibodies. Sera from patients with GT with or without anti-αIIbβ3 isoantibodies were then used to study their in vitro effect on platelets from healthy donors. We used several approaches (IgG purification, immunofluorescence staining, and inhibition of signaling pathways) to characterize the pathogenic properties of the anti-αIIbβ3 isoantibodies.

Results

Only 2 samples were able to severely block integrin function. We observed that these 2 sera caused a reduction in platelet size similar to that observed when platelets become procoagulant. Mixing healthy donor platelets with patients' sera or purified IgGs led to microvesiculation, phosphatidylserine exposure, and induction of calcium influx. This was associated with an increase in procoagulant platelets. Pore formation and calcium entry were associated with complement activation, leading to the constitution of a membrane attack complex (MAC) with enhanced complement protein C5b-9 formation. This process was inhibited by the complement 5 inhibitor eculizumab and reduced by polyvalent human immunoglobulins.

Conclusion

Our data suggest that complement activation induced by rare blocking anti-αIIbβ3 isoantibodies may lead to the formation of a MAC with subsequent pore formation, resulting in calcium influx and procoagulant platelet phenotype.

Multidisciplinary management of a pregnancy complicated by Glanzmann thrombasthenia: A case report

BACKGROUND

Glanzmann thrombasthenia (GT) is a rare, autosomal recessive disorder of platelet glycoprotein IIb-IIIa receptors. Pregnant patients with GT are at increased risk of maternal and fetal bleeding. There is a paucity of literature on the peripartum management of patients.

CASE DESCRIPTION

We present the antepartum through the postpartum course of a patient with GT who was managed by a multidisciplinary approach that included communication across maternal-fetal medicine, hematology, transfusion medicine, and anesthesiology services. In addition to routine prepartum obstetric imaging and hematologic laboratory studies, we proactively monitored the patient for anti-platelet antibodies every 4-6 weeks to gauge the risk for neonatal alloimmune thrombocytopenia. Furthermore, we prioritized uterotonics, tranexamic acid, and transfusion of HLA-matched platelets to manage bleeding for mother and fetus intrapartum through the postpartum periods.

CONCLUSION

To date, there are limited guidelines for managing bleeding or preventing alloimmunization during pregnancy in patients with GT. Here, we present a complex case with aggressive management of bleeding prophylactically for the mother while serially monitoring both mother and fetus for peripartum bleeding risks and events. Moreover, future studies warrant continued evaluation of these approaches to mitigate increased bleeding risks in subsequent pregnancies.

A lethal case of massive hemorrhage after percutaneous liver biopsy in a patient with thrombasthenia

Percutaneous needle liver biopsy is an important procedure in the diagnosis of and assessment of the severity of liver diseases. Although liver biopsy is considered to be a relatively safe procedure, there are occasional cases of death due to massive bleeding after liver biopsy. Thrombasthenia is a disease in which bleeding occurs in the mucosa and skin due to platelet dysfunction. A 60-year-old female was admitted for a liver biopsy for further investigation after an abnormal liver function test. She was diagnosed with thrombasthenia and was being treated with oral tranexamic acid and carbazochrome. Blood tests showed little decrease of platelet count and no abnormalities of blood coagulability. Approximately ten hours after the liver biopsy, the patient complained of nausea and lightheadedness, followed by decreased blood pressure and decreased consciousness. An emergent abdominal CT scan showed a large amount of blood in the abdominal cavity. The patient died despite multidisciplinary treatment, and a forensic autopsy was performed. At internal examination, approximately 2,620 mL of dark red blood was accumulated in the abdominal cavity. A puncture wound led 1.8 cm into the liver from the surface of the liver, and no major vascular damage was observed. The cause of death was considered to be blood loss due to bleeding from the puncture wound. Even if the platelet count is normal, such as in a case of thrombasthenia, the risk of bleeding should not be underestimated. Careful attention should be paid when performing liver biopsy in a patient with risk factors.

Amplified inhibition of atherosclerotic plaque-induced platelet activation by glenzocimab with dual antiplatelet therapy

BACKGROUND

Aspirin and platelet P2Y12 inhibitors, such as ticagrelor, suboptimally inhibit microvascular thrombosis during ST-elevation myocardial infarction. Glycoprotein (GP) IIb/IIIa inhibitors may further inhibit this but cause excessive bleeding.

OBJECTIVES

We investigated whether combination of glenzocimab, a GPVI inhibitor, with aspirin and ticagrelor provides additional antithrombotic effects, as GPVI has a critical role in atherothrombosis but minimal involvement in hemostasis.

METHODS

We investigated the effects of glenzocimab (monoclonal antibody Fab fragment) using blood from healthy donors and patients with acute coronary syndrome treated with aspirin and ticagrelor. Platelets were stimulated with multiple agonists, including atherosclerotic plaque, from patients undergoing carotid endarterectomy.

RESULTS

Aspirin and ticagrelor partially inhibited atherosclerotic plaque-induced platelet aggregation by 48% compared with control (34 ± 3 vs 65 ± 4 U; P < .001). Plaque-induced platelet aggregation, adhesion, secretion, and activation were critically dependent on GPVI activation. Glenzocimab alone reduced plaque-induced aggregation by 75% compared with control (16 ± 4 vs 65 ± 4 U; P < .001) and by >95% when combined with aspirin and ticagrelor (3 ± 1 vs 65 ± 4 U; P < .001). Glenzocimab reduced platelet aggregation, adhesion, and thrombin generation when added to blood of aspirin- and ticagrelor-treated patients with acute coronary syndrome. Glenzocimab shared several antithrombotic effects with the GPIIb/IIIa inhibitor eptifibatide with less effect on general hemostasis assessed by rotational thromboelastometry. In a murine intravital model of ST-elevation myocardial infarction, genetic depletion of GPVI reduced microvascular thrombosis.

CONCLUSION

Addition of glenzocimab to aspirin and ticagrelor enhances platelet inhibition via multiple mechanisms of atherothrombosis. Compared with a GPIIb/IIIa inhibitor, glenzocimab shares multiple antithrombotic effects, with less inhibition of mechanisms involved in general hemostasis.

Primary Hemostasis Disorders as a Cause of Heavy Menstrual Bleeding in Women of Reproductive Age

Heavy menstrual bleeding (HMB) is a common clinical condition affecting adolescent and adult women and compromising their quality of life. Primary hemostasis disorders, affecting platelet plug formation, can be the underlying cause of HMB. They comprise a heterogeneous group of diseases with Von Willebrand disease (VWD) being the most commonly diagnosed; other disorders in this group that have been linked to HMB include (a) Glanzmann thrombasthenia, (b) Bernard-Soulier syndrome, (c) Hermansky-Pudlak syndrome, (d) immune thrombocytopenia (ITP), and (e) Ehlers-Danlos syndromes (EDS) and hypermobility spectrum disorders (HSD). Diagnosing these diseases can be challenging, as the basic laboratory investigations can be within the normal range. Thus, identification of specific clinical features and a thorough hematologic workup can be very important, providing the correct diagnosis. Proper diagnosis of the underlying disorder is important, as management may vary accordingly. Although disease-specific management guidelines exist for some of these disorders such as VWD and ITP, due to the rarity of most primary hemostasis disorders, the best approach for the management of HMB in these women remains elusive. The goal of this study was to create an informative, comprehensive review of the primary hemostasis disorders that have been linked to HMB. This study provides a summary of the basic published information regarding epidemiology, pathophysiology, clinical phenotype, diagnosis, and treatment of HMB in those diseases and serves as a reference guide for further reading.

Glycoprotein VI interplay with fibrin(ogen) in thrombosis

Platelets play a central role in the arrest of bleeding. The ability of platelets to engage with extracellular matrix proteins of the subendothelium has long been recognized as a pivotal platelet attribute, underpinning adequate hemostasis. The propensity of platelets to rapidly bind and functionally respond to collagen was one of the earliest documented events in platelet biology. The receptor primarily responsible for mediating platelet/collagen responses was identified as glycoprotein (GP) VI and successfully cloned in 1999. Since that time, this receptor has held the attention of many research groups, and through these efforts, we now have an excellent understanding of the roles of GPVI as a platelet- and megakaryocyte-specific adheso-signaling receptor in platelet biology. GPVI is considered a viable antithrombotic target, as data obtained from groups across the world is consistent with GPVI being less involved in physiological hemostatic processes but participating in arterial thrombosis. This review will highlight the key aspects of GPVI contributions to platelet biology and concentrate on the interaction with recently identified ligands, with a focus on fibrin and fibrinogen, discussing the role of these interactions in the growth and stability of thrombi. We will also discuss important therapeutic developments that target GPVI to modulate platelet function while minimizing bleeding outcomes.

Emergency management of patients with Glanzmann thrombasthenia: consensus recommendations from the French reference center for inherited platelet disorders

Glanzmann thrombasthenia (GT) is a genetic bleeding disorder characterised by severely reduced/absent platelet aggregation in response to multiple physiological agonists. The severity of bleeding in GT varies markedly, as does the emergency situations and complications encountered in patients. A number of emergency situations may occur in the context of GT, including spontaneous or provoked bleeding, such as surgery or childbirth. While general management principles apply in each of these settings, specific considerations are essential for the management of GT to avoid escalating minor bleeding events. These recommendations have been developed from a literature review and consensus from experts of the French Network for Inherited Platelet Disorders, the French Society of Emergency Medicine, representatives of patients' associations, and Orphanet to aid decision making and optimise clinical care by non-GT expert health professionals who encounter emergency situations in patients with GT.

The WASH-complex subunit Strumpellin regulates integrin αIIbβ3 trafficking in murine platelets

The platelet specific integrin αIIbβ3 mediates platelet adhesion, aggregation and plays a central role in thrombosis and hemostasis. In resting platelets, αIIbβ3 is expressed on the membrane surface and in intracellular compartments. Upon activation, the number of surface-expressed αIIbβ3 is increased by the translocation of internal granule pools to the plasma membrane. The WASH complex is the major endosomal actin polymerization-promoting complex and has been implicated in the generation of actin networks involved in endocytic trafficking of integrins in other cell types. The role of the WASH complex and its subunit Strumpellin in platelet function is still unknown. Here, we report that Strumpellin-deficient murine platelets display an approximately 20% reduction in integrin αIIbβ3 surface expression. While exposure of the internal αIIbβ3 pool after platelet activation was unaffected, the uptake of the αIIbβ3 ligand fibrinogen was delayed. The number of platelet α-granules was slightly but significantly increased in Strumpellin-deficient platelets. Quantitative proteome analysis of isolated αIIbβ3-positive vesicular structures revealed an enrichment of protein markers, which are associated with the endoplasmic reticulum, Golgi complex and early endosomes in Strumpellin-deficient platelets. These results point to a so far unidentified role of the WASH complex subunit Strumpellin in integrin αIIbβ3 trafficking in murine platelets.

Pathological Background and Clinical Procedures in Oral Surgery Haemostasis Disorders: A Narrative Review

Haemostasis disorders are serious pathologies that could put dental and surgical procedures at risk as they are associated with postoperative bleeding, which in some circumstances could be prolonged and dangerous for the patient. In-depth knowledge of the problems associated with coagulation pathologies and the suitable specific procedures should be implemented in dental practice. A good awareness of the clinical protocols to be used in these circumstances may help reduce operator stress and increase patient compliance. Collaboration with the haematologist is always recommended to establish an adequate treatment plan, both regarding the administration of therapies that promote haemostasis and for assessing the operative risk. Hereby, we summarize the congenital and hereditary pathologies that lead to haemostasis disorders, which can be found in patients undergoing dental procedures. The purpose of this narrative review is to frame the diseases from a clinical, anamnestic, and etiopathological standpoint, as well as to evaluate an operative approach to the pathology under consideration, with particular attention to anaesthesia manoeuvres and post-surgical haemostasis, to avoid hematoma formation and uncontrolled bleeding which can lead procedure failure up and even death. Of note, it is likewise important to educate the patient about prevention, to keep the oral cavity healthy and avoid invasive procedures, limiting the number of operative sessions.

Glanzmann Thrombasthenia in Pakistani Patients: Identification of 7 Novel Pathogenic Variants in the Fibrinogen Receptor αIIbβ3

Glanzmann thrombasthenia (GT) is a rare autosomal recessive inherited platelet disorder occurring frequently in populations with high incidence of consanguineous marriages. GT is characterized by quantitative and/or qualitative defect of the platelet αIIbβ3 (GPIIb/IIIa) receptor caused by pathogenic variants of the encoding genes: ITGA2B and ITGB3. Patients present with a moderate to severe bleeding tendency with normal platelet count. Platelets show reduced/absent aggregation for all agonists except ristocetin in light transmission aggregometry and reduced/absent αIIbβ3 expression in flow cytometry (FC). In this study, we investigated a cohort of 20 Pakistani patients and 2 families collected from the National Institute of Blood Disease, Karachi and Chughtai's Lab, Lahore. Platelet aggregation studies, FC (platelet CD41, CD61, CD42a, CD42b) and direct sequencing of the candidate genes were performed. All patients showed altered platelet aggregation, but normal agglutination after stimulation with ristocetin. Absent/reduced αIIbβ3 receptor expression was present in the platelets of 16 patients, in 4 patients expression was borderline/normal. Candidate gene sequencing identified pathogenic/likely pathogenic variants in 15 patients. Seven variants are novel. One patient with absent receptor expression remained without genetic finding. 13 (86.7%) of 15 patients stated consanguinity reflected by homozygosity finding in 14 (93.3%) patients.

Prevalence of hemorrhagic ovarian cysts in patients with rare inherited bleeding disorders

BACKGROUND

In comparison with the general population, women with bleeding disorders are more prone to develop obstetrical and gynecological problems. However, no comprehensive evaluation has investigated the prevalence of hemorrhagic ovarian cysts (HOCs) in rare bleeding disorders (RBDs). In this study, we sought to determine the prevalence of HOCs in a large cohort of Iranian patients with RBDs.

METHODS

A total of 210 symptomatic patients suspected of HOCs with RBD were included. The median age of the study population was 24 years. Patients were diagnosed with fibrinogen disorders (n = 7, 3%), factor (F) II (n = 4, 2%), FV (n = 28, 13%), FVII (n = 4, 2%), FX (n = 6, 3%), FXIII (n = 122, 58%), combined FV and FVIII (n = 8, 4%), Glanzmann's thrombasthenia (n = 10, 5%), and von Willebrand disease (VWD) type 3 (n = 21, 10%).

RESULTS

Following further clinical and ultrasound examinations of these 210 patients, 68 (32.4%) were confirmed with a diagnosis of HOCs. Of which, FXIII deficiency with 46 cases (67.6%), followed by VWD type 3 (6 cases, 8.8%) showed the highest number. Other coagulation defects associated with HOCs were including fibrinogen deficiency (n = 2, 3%), FII (n = 2, 3%), FV (n = 4, 6%), FVII (n = 2, 3%), FX (n = 1, 1.5%), combined FV and FVIII (n = 2, 3%), and Glanzmann's thrombasthenia (n = 3, 4.5%).

CONCLUSION

This study found a high prevalence of HOCs in patients with RBDs, indicating the importance of early diagnosis and optimal management of obstetric and gynecological complications in these patients.

Description and Clinical Management of Patients With Glanzmann's Thrombasthenia in a University Hospital, a Referral Center Specialized in Hemostasis, in Bogotá, Colombia

Introduction Glanzmann's thrombasthenia (GT) is an autosomal recessive disorder of platelets caused by a deficiency in the glycoprotein IIb-IIIa. Bleeding from the skin, mucous membranes, and ecchymosis are symptoms manifested starting in early childhood. There may also be major bleeding conditions as a result of surgical procedures or trauma. The treatment is based on platelet transfusions, antifibrinolytic agents, and recombinant activated factor VII (rFVIIa). Objective To describe the demographic and clinical characteristics as well as the main treatment strategies used during bleeding events or procedures for patients diagnosed with GT that required inpatient attention at a university hospital, a referral center specialized in hemostasis, in the city of Bogota. Materials and methods A descriptive retrospective cohort study was done over a period of 10 years that included nine patients over 18 years of age diagnosed with GT. Results A total of 34 admissions were reported, 23 due to bleeding and 11 for scheduled surgery. Some of the admissions for bleeding (38%) (n=13) required surgical procedures. Overall, 23 surgical procedures were done, six of which were classified as major. Seventy-seven percent of the patients were women with a median age of 37. Their most common symptoms were mucosal and genitourinary bleeding. The use of antifibrinolytics was registered in 28 events, followed by the use of platelet transfusion in 19, and the use of rFVIIa in 17. The average hospital stay was eight days. Conclusion The characteristics registered and the treatments established for this cohort of Colombian patients with GT are similar to those reported in other hospitals around the world. GT presents diagnostic and therapeutic challenges and, therefore, acquiring more knowledge about this pathology is needed within this context.

Lockdown, a selective small-molecule inhibitor of the integrin phosphatase PPM1F, blocks cancer cell invasion

Phosphatase PPM1F is a regulator of cell adhesion by fine-tuning integrin activity and actin cytoskeleton structures. Elevated expression of this enzyme in human tumors is associated with high invasiveness, enhanced metastasis, and poor prognosis. Thus, PPM1F is a target for pharmacological intervention, yet inhibitors of this enzyme are lacking. Here, we use high-throughput screening to identify Lockdown, a reversible and non-competitive PPM1F inhibitor. Lockdown is selective for PPM1F, because this compound does not inhibit other protein phosphatases in vitro and does not induce additional phenotypes in PPM1F knockout cells. Importantly, Lockdown-treated glioblastoma cells fully re-capitulate the phenotype of PPM1F-deficient cells as assessed by increased phosphorylation of PPM1F substrates and corruption of integrin-dependent cellular processes. Ester modification yields Lockdown^Pro with increased membrane permeability and prodrug-like properties. Lockdown^Pro suppresses tissue invasion by PPM1F-overexpressing human cancer cells, validating PPM1F as a therapeutic target and providing an access point to control tumor cell dissemination.

Activated Platelets Upregulate β2 Integrin Mac-1 (CD11b/CD18) on Dendritic Cells, Which Mediates Heterotypic Cell-Cell Interaction

Recent evidence suggests interaction of platelets with dendritic cells (DCs), while the molecular mechanisms mediating this heterotypic cell cross-talk are largely unknown. We evaluated the role of integrin Mac-1 (αMβ2, CD11b/CD18) on DCs as a counterreceptor for platelet glycoprotein (GP) Ibα. In a dynamic coincubation model, we observed interaction of human platelets with monocyte-derived DCs, but also that platelet activation induced a sharp increase in heterotypic cell binding. Inhibition of CD11b or GPIbα led to significant reduction of DC adhesion to platelets in vitro independent of GPIIbIIIa, which we confirmed using platelets from Glanzmann thrombasthenia patients and transgenic mouse lines on C57BL/6 background (GPIbα^-/-, IL4R-GPIbα-tg, and muMac1 mice). In vivo, inhibition or genetic deletion of CD11b and GPIbα induced a significant reduction of platelet-mediated DC adhesion to the injured arterial wall. Interestingly, only intravascular antiCD11b inhibited DC recruitment, suggesting a dynamic DC-platelet interaction. Indeed, we could show that activated platelets induced CD11b upregulation on Mg²⁺-preactivated DCs, which was related to protein kinase B (Akt) and dependent on P-selectin and P-selectin glycoprotein ligand 1. Importantly, specific pharmacological targeting of the GPIbα-Mac-1 interaction site blocked DC-platelet interaction in vitro and in vivo. These results demonstrate that cross-talk of platelets with DCs is mediated by GPIbα and Mac-1, which is upregulated on DCs by activated platelets in a P-selectin glycoprotein ligand 1-dependent manner.

How I manage pregnancy in women with Glanzmann thrombasthenia

Glanzmann thrombasthenia (GT) is a rare inherited platelet function disorder caused by a quantitative and/or qualitative defect of the αIIbβ3 integrin. Pregnancy and delivery is a recognized risk period for bleeding in women with GT. The newborn may also be affected by fetal and neonatal immune thrombocytopenia induced by the transplacental passage of maternal anti-αIIbβ3 antibodies, which can lead to severe hemorrhage and fetal loss. Pregnancy in GT women thus requires a multidisciplinary approach, including prepregnancy counseling, and a treatment plan for delivery for both the mother and child. In this article, we summarize the current knowledge on pregnancy in women with GT and describe how we manage this severe platelet disorder in our clinical practice.

Analysis of Integrin αIIb Subunit Dynamics Reveals Long-Range Effects of Missense Mutations on Calf Domains

Integrin α_IIbβ₃, a glycoprotein complex expressed at the platelet surface, is involved in platelet aggregation and contributes to primary haemostasis. Several integrin α_IIbβ₃ polymorphisms prevent the aggregation that causes haemorrhagic syndromes, such as Glanzmann thrombasthenia (GT). Access to 3D structure allows understanding the structural effects of polymorphisms related to GT. In a previous analysis using Molecular Dynamics (MD) simulations of α_IIbCalf-1 domain structure, it was observed that GT associated with single amino acid variation affects distant loops, but not the mutated position. In this study, experiments are extended to Calf-1, Thigh, and Calf-2 domains. Two loops in Calf-2 are unstructured and therefore are modelled expertly using biophysical restraints. Surprisingly, MD revealed the presence of rigid zones in these loops. Detailed analysis with structural alphabet, the Proteins Blocks (PBs), allowed observing local changes in highly flexible regions. The variant P741R located at C-terminal of Calf-1 revealed that the Calf-2 presence did not affect the results obtained with isolated Calf-1 domain. Simulations for Calf-1 + Calf-2, and Thigh + Calf-1 variant systems are designed to comprehend the impact of five single amino acid variations in these domains. Distant conformational changes are observed, thus highlighting the potential role of allostery in the structural basis of GT.

Gastrointestinal Bleeding in Congenital Bleeding Disorders

Gastrointestinal bleeding (GIB) is serious, intractable, and potentially life-threatening condition. There is considerable heterogeneity in GIB phenotypes among congenital bleeding disorders (CBDs), making GIB difficult to manage. Although GIB is rarely encountered in CBDs, its severity in some patients makes the need for a comprehensive and precise assessment of underlying factors and management approaches imperative. Initial evaluation of GIB begins with assessment of hematological status; GIB should be ruled out in patients with chronic anemia, and in presentations that include hematemesis, hematochezia, or melena. High-risk patients with recurrent GIB require urgent interventions such as replacement therapy for treatment of coagulation factor deficiency (CFD). However, the best management strategy for CFD-related bleeding remains controversial. While several investigations have identified CBDs as potential risk factors for GIB, research has focused on assessing the risks for individual factor deficiencies and other CBDs. This review highlights recent findings on the prevalence, management strategies, and alternative therapies of GIB related to CFDs, and platelet disorders.

Glanzmann Thrombasthenia: Use of the Soft Splint with Tranexamic Acid Paste to Reduce Spontaneous Oral Bleeding

Background

Glanzmann thrombasthenia is a rare bleeding disorder due to defects in the glycoprotein Ilb/IIIa complex present on the platelet membrane. The most common mode of treatment for this disorder is platelet transfusion. However, scientific evidence does state that repeated transfusions could lead to auto immunization making transfusions ineffective.

Aim and objective

To describe the use of a novel technique of soft splint with tranexamic acid paste to stop oral bleeding in a patient with Glanzmann thrombasthenia (GT).

Case description

A 7-year-old female patient with a known history of GT was referred to the pediatric department. The chief complaint of the patient revealed a history of spontaneous bleeding from the oral cavity. The patient required multiple teeth extractions due to severely carious teeth. History revealed that the patient was admitted to the hospital (casualty) three times within 1 month due to a similar complaint leading to hypovolemic shock. Several transfusion procedures were done to stop the spontaneous bleeding. To stop the intraoral bleeding without transfusions, a novel method of using a soft splint with tranexamic acid paste (500 mg tablet crushed and mixed with saline) in the area of spontaneous bleeding was employed with a successful follow-up of 7 months.

Conclusion

Soft splint with the tranexamic acid paste can serve as an effective method of treatment for patients with spontaneous oral bleeding due to medical conditions like GT.

Clinical relevance

This case report highlights the need for awareness among all the healthcare providers about the importance of regular dental visits. The healthcare providers also need to emphasize the same to all patients with medical conditions to avoid such life-threatening situations.

How to cite this article

Bhavyaa R, Vignesh KC, Muthu MS, et al. Glanzmann Thrombasthenia: Use of the Soft Splint with Tranexamic Acid Paste to Reduce Spontaneous Oral Bleeding. Int J Clin Pediatr Dent 2021;14(4):580–585.

Use of rFVIIa in Preventing Recurrent Intra-articular Hemorrhages in a 15-Year-Old Patient With Glanzmann Thrombasthenia

Glanzmann thrombasthenia is a rare congenital thrombocytopathy. The first-line treatment in severe life-threatening bleeding is a transfusion of platelet concentrate or recombinant factor VIIa in the case of platelet transfusion refractoriness. We present the case of a 16-year-old boy with Glanzmann thrombasthenia who was admitted to hospital with severe bleeding into the quadriceps femoris muscle. At the age of 15 years, he was hospitalized again because of chronic bleeding into the right ankle joint, resulting in joint destruction. Here we give a scheme of management and treatment of this patient. Hemostatic therapy followed by radiosynovectomy of the right ankle joint and introduction of secondary preventive treatment with recombinant factor VIIa proved to be efficacious and safe.

Characterization of the Role of Integrin α5β1 in Platelet Function, Hemostasis, and Experimental Thrombosis

Objective  Integrins are key regulators of various platelet functions. The pathophysiological importance of most platelet integrins has been investigated, with the exception of α5β1, a receptor for fibronectin. The aim of this study was to characterize the role of α5β1 in megakaryopoiesis, platelet function, and to determine its importance in hemostasis and arterial thrombosis.

Approach and Results  We generated a mouse strain deficient for integrin α5β1 on megakaryocytes and platelets (PF4Cre-α5 ^−/− ). PF4Cre-α5 ^−/− mice were viable, fertile, and presented no apparent signs of abnormality. Megakaryopoiesis appears unaltered as evidence by a normal megakaryocyte morphology and development, which is in agreement with a normal platelet count. Expression of the main platelet receptors and the response of PF4Cre-α5 ^−/− platelets to a series of agonists were all completely normal. Adhesion and aggregation of PF4Cre-α5 ^−/− platelets under shear flow on fibrinogen, laminin, or von Willebrand factor were unimpaired. In contrast, PF4Cre-α5 ^−/− platelets displayed a marked decrease in adhesion, activation, and aggregation on fibrillar cellular fibronectin and collagen. PF4Cre-α5 ^−/− mice presented no defect in a tail-bleeding time assay and no increase in inflammatory bleeding in a reverse passive Arthus model and a lipopolysaccharide pulmonary inflammation model. Finally, no defects were observed in three distinct experimental models of arterial thrombosis based on ferric chloride-induced injury of the carotid artery, mechanical injury of the abdominal aorta, or laser-induced injury of mesenteric vessels.

Conclusion  In summary, this study shows that platelet integrin α5β1 is a key receptor for fibrillar cellular fibronectin but is dispensable in hemostasis and arterial thrombosis.

Flow cytometric analysis of platelet surface glycoproteins in the diagnosis of thirty-two Turkish patients with Glanzmann thrombasthenia: a multicenter experience

Background/aim

Glanzmann thrombasthenia (GT) is a rare autosomal recessively inherited bleeding disorder characterized by the quantitative (type 1 and type 2) or qualitative (type 3) deficiency in platelet membrane glycoprotein (GP) IIb/IIIa (CD41a/CD61) fibrinogen receptors. In type 1, 2, and 3, CD41a/CD61 expression is 5%, 5%–20% and above 20%, respectively. In this study, diagnosis of GT was confirmed and subgroups were identified in 32 Turkish patients by flow cytometry analysis.

Materials and methods

CD41a/CD61 expression levels in platelet-rich plasma (PRP) obtained from peripheral venous EDTA blood samples were analyzed with a BD FACSCanto II flow cytometer (Becton Dickinson, Franklin Lakes, NJ, USA). GT subgroup analysis was performed by counting 50,000 events in the BD FACSDiva Software v6.1.3 program of the instrument.

Results

In the present study, in blood samples of 32 patients from 23 families with GT and 22 healthy controls, co-expression levels of CD41a and CD61 in PRP was analyzed. 12 out of 23 families were consistent with type 1 GT (52.2%), 4 were consistent with type 2 GT (17.4%), and 7 were consistent with type 3 GT (30.4%).

Conclusion

Especially due to consanguineous marriages, GT with various glycoprotein levels may be detected. As a result of the flow cytometry analysis of the present study with the highest GT patient population in Turkey, type 1 GT patients were the most common subgroup. In the determination of the GT subgroups; especially in the detection of type 3 GT, flow cytometry is the most sensitive glycoprotein analysis method. In addition to light transmission aggregometry, CD41a/CD61 study by flow cytometer confirms diagnosis when mutation analysis cannot be performed.

A Novel Homozygous Frameshift Mutation in ITGB3 Causes Glanzmann's Thrombasthenia

The objective of this study was to elucidate the molecular characteristics of a Chinese family with Glanzmann's thrombasthenia (GT). The proband was diagnosed with GT based on clinical manifestations, platelet aggregation, and the expression of CD41 and CD61 in platelets. Whole-exome and Sanger sequencing were used to detect genetic defects related to GT in the proband and the family of the pedigree. Whole-exome sequencing showed a c.1784-1802delinsGTCACA, p. S595Cfs*70 homozygous mutation in exon 11 of the ITGB3 gene in the proband. Heterozygous mutations were found in the proband's parents, grandmother, uncle, aunt, and younger brother. This novel p. S595Cfs*70 ITGB3 gene mutation is not present in the 1000 Genomes and ExAC databases.

Glanzmann Thrombasthenia: Perspectives from Clinical Practice on Accurate Diagnosis and Optimal Treatment Strategies

Glanzmann thrombasthenia (GT) is a rare autosomal recessive disorder of fibrinogen-mediated platelet aggregation due to a quantitative or qualitative deficit of the α_IIbβ₃ integrin at the platelet surface membrane resulting from mutation(s) in ITGA2B and/or ITGB3. Patients tend to present in early childhood with easy bruising and mucocutaneous bleeding. The diagnostic process requires consideration of more common disorders of haemostasis and coagulation prior to confirming the disorder with platelet light transmission aggregation, flow cytometry of CD41 and CD61 expression, and/or exon sequencing of ITGA2B and ITGB3. Antifibrinolytic therapy, recombinant activated factor VII, and platelet transfusions are the mainstay of therapy, although the latter may trigger formation of anti-platelet antibodies in GT patients and inadvertent platelet-refractory disease. The management of these patients therefore remains complex, particularly in the context of trauma, labour and delivery, and perioperative care. Bone marrow transplantation remains the sole curative option, although the venue of gene therapy is being increasingly explored as a future alternative for definitive treatment of GT.

Itgb3-integrin-deficient mice may not be a sufficient model for patients with Glanzmann thrombasthenia

Itgb3-integrin-deficient (Itgb3^−/−) mice have been reported as a Glanzmann thrombasthenia (GT) model and have been used for platelet research. However, it remains unclear whether this mouse model can fully simulate patients with GT or whether it has different characteristics from these patients. The present study aimed to answer this question. Itgb3^−/− mice were tested for platelet function, tail bleeding, whole-blood count, bone marrow hematopoiesis and organ enlargement. Itgb3^−/− platelets showed impaired functions, including fibrinogen binding, aggregation, adhesion or spreading. Itgb3^−/− mice demonstrated decreased platelet count and microcytic hypochromic anemia. Reduced iron staining of bone marrow and decreased plasma ferritin level confirmed the diagnosis of iron deficiency anemia. Evident splenomegaly was observed in Itgb3^−/− mice. Immunohistochemical analysis of spleen biopsy revealed normal expression of CD3 and CD19, but elevated expression of CD71, which suggested that the splenomegaly in Itgb3^−/− mice may be associated with extramedullary hematopoiesis. In conclusion, Itgb3^−/− mice exhibited some unique characteristics that differed from those of human patients with GT and thus cannot completely simulate patients with GT.

Exogenous Integrin αIIbβ3 Inhibitors Revisited: Past, Present and Future Applications

The integrin αIIbβ3 is the most abundant integrin on platelets. Upon platelet activation, the integrin changes its conformation (inside-out signalling) and outside-in signalling takes place leading to platelet spreading, platelet aggregation and thrombus formation. Bloodsucking parasites such as mosquitoes, leeches and ticks express anticoagulant and antiplatelet proteins, which represent major sources of lead compounds for the development of useful therapeutic agents for the treatment of haemostatic disorders or cardiovascular diseases. In addition to hematophagous parasites, snakes also possess anticoagulant and antiplatelet proteins in their salivary glands. Two snake venom proteins have been developed into two antiplatelet drugs that are currently used in the clinic. The group of proteins discussed in this review are disintegrins, low molecular weight integrin-binding cysteine-rich proteins, found in snakes, ticks, leeches, worms and horseflies. Finally, we highlight various oral antagonists, which have been tested in clinical trials but were discontinued due to an increase in mortality. No new αIIbβ3 inhibitors are developed since the approval of current platelet antagonists, and structure-function analysis of exogenous disintegrins could help find platelet antagonists with fewer adverse side effects.

Thrombocytopathies: Not Just Aggregation Defects-The Clinical Relevance of Procoagulant Platelets

Platelets are active key players in haemostasis. Qualitative platelet dysfunctions result in thrombocytopathies variously characterized by defects of their adhesive and procoagulant activation endpoints. In this review, we summarize the traditional platelet defects in adhesion, secretion, and aggregation. In addition, we review the current knowledge about procoagulant platelets, focusing on their role in bleeding or thrombotic pathologies and their pharmaceutical modulation. Procoagulant activity is an important feature of platelet activation, which should be specifically evaluated during the investigation of a suspected thrombocytopathy.

A microchip flow-chamber assay screens congenital primary hemostasis disorders

BACKGROUND

Von Willebrand disease (VWD) and platelet function disorders (PFDs) are congenital bleeding disorders caused by primary hemostasis defects. Platelet function tests are time-consuming and require considerable amounts of blood sample, and there have been no easy-to-use assays for assessing platelet function quickly and sensitively. We report the usefulness of a microchip flow-chamber system (T-TAS^® ) for detecting and/or predicting clinical severity in patients with VWD type 1 and type 2N and platelet storage pool disease. Here, we developed an application of a screening assay for primary hemostasis disorders.

METHODS

Microchips coated with collagen (PL-chip) and collagen/thromboplastin (AR-chip) were utilized to evaluate platelet thrombus formation (PTF) at high shear and fibrin-rich PTF at low shear, respectively, in whole blood samples from 22 patients with VWD (16 type 2A, four type 2B, two type 3) and four patients with PFDs (two BSS, two Glanzmann thrombasthenia). The time-to-increase by 10 kPa (T₁₀ ) was calculated from flow pressure curves. Also, whole blood-induced platelet aggregation was assessed using Multiplate^® analysis.

RESULTS

PL-chip T₁₀ values ≥10 min successfully distinguished patients with all types of VWD and PFDs from healthy controls, irrespective of age, bleeding scores, and von Willebrand factor levels. However, AR-chip assay incompletely distinguished between type 2A patients and healthy ones. Multiplate analysis permitted screening of PFDs and type 3 VWD, but values in type 2A partially overlapped with those in controls. PL-chip assay did not reflect the clinical severity in these patients.

CONCLUSIONS

T-TAS with PL-chip could be a quick screening tool for congenital primary hemostasis disorder, VWD, and PFDs.

Immunization against αIIb β3 and αv β3 in Glanzmann thrombasthenia patients carrying the French Gypsy mutation

Essentials The c.1544+1G>A mutation was identified in Gypsy Glanzmann thrombasthenia (GT) patients. Gypsy GT patients express normal αv β3 carrying HPA-1b epitopes. To demonstrate HPA-1a alloimmunization by modified antigen capture assays. Gypsy GT patients could develop anti-HPA-1a alloantibodies against β3 and αv β3 . ABSTRACT: Background Glanzmann thrombasthenia (GT) is a rare bleeding disorder caused by the absence or the dysfunction of the platelet αIIb β3 integrin. A founder mutation in the ITGA2B gene was previously identified in French Gypsy patients. Interestingly, this mutation was strongly linked to the human platelet antigen-1b (HPA-1b). The HPA-1bb Gypsy patients are at risk of isoimmunization against αIIb β3 , as this complex is not expressed at their platelet surface. Tentatively, they would, however, not have an increased risk of developing anti-HPA-1a alloantibodies by exposure of αIIb β3 on platelets from random platelet transfusions. However, the β3 chain can also associate with the αv subunit expressed at the platelet surface. Because Gypsy GT patients express normal αv β3 carrying HPA-1b epitopes, these patients might develop anti-HPA-1a alloantibodies reacting with αv β3 and/or β3 . Objectives/Patients/Methods To demonstrate this hypothesis, sera from HPA-1bb (n = 5) and HPA-1ab (n = 1) Gypsy GT patients were investigated by modified antigen capture assay using platelets or stable transfected cells. Furthermore, stable transfected cells expressing either αIIb β3 or αv β3 together with soluble monomeric chimeric β3 (as absorbent) were used to differentiate anti-β3 and anti-αv β3 reactivity. Results Only HPA-1bb patients developed alloantibodies reacting with HPA-1a cells. Further analysis showed that HPA-1bb patients developed anti-HPA-1a alloantibodies reacting with β3 and/or αv β3 . Conclusion In this study, we found that HPA-1bb patients who failed to express αIIb β3 on the platelet surface can develop alloantibodies against HPA-1a reacting with β3 as well as αv β3 . This is of particular importance as anti-HPA-1a alloantibodies might cause fetal neonatal alloimmune thrombocytopenia and/or platelet transfusion refractoriness.

Characterization of Procoagulant COAT Platelets in Patients with Glanzmann Thrombasthenia

Patients affected by the rare Glanzmann thrombasthenia (GT) suffer from defective or low levels of the platelet-associated glycoprotein (GP) IIb/IIIa, which acts as a fibrinogen receptor, and have therefore an impaired ability to aggregate platelets. Because the procoagulant activity is a dichotomous facet of platelet activation, diverging from the aggregation endpoint, we were interested in characterizing the ability to generate procoagulant platelets in GT patients. Therefore, we investigated, by flow cytometry analysis, platelet functions in three GT patients as well as their ability to generate procoagulant collagen-and-thrombin (COAT) platelets upon combined activation with convulxin-plus-thrombin. In addition, we further characterized intracellular ion fluxes during the procoagulant response, using specific probes to monitor by flow cytometry kinetics of cytosolic calcium, sodium, and potassium ion fluxes. GT patients generated higher percentages of procoagulant COAT platelets compared to healthy donors. Moreover, they were able to mobilize higher levels of cytosolic calcium following convulxin-plus-thrombin activation, which is congruent with the greater procoagulant activity. Further investigations will dissect the role of GPIIb/IIIa outside-in signalling possibly implicated in the regulation of platelet procoagulant activity.

Novel SOX10 Mutations in Waardenburg Syndrome: Functional Characterization and Genotype-Phenotype Analysis

Waardenburg syndrome (WS) is a prevalent hearing loss syndrome, concomitant with focal skin pigmentation abnormalities, blue iris, and other abnormalities of neural crest-derived cells, including Hirschsprung’s disease. WS is clinically and genetically heterogeneous and it is classified into four major types WS type I, II, III, and IV (WS1, WS2, WS3, and WS4). WS1 and WS3 have the presence of dystopia canthorum, while WS3 also has upper limb anomalies. WS2 and WS4 do not have the dystopia canthorum, but the presence of Hirschsprung’s disease indicates WS4. There is a more severe subtype of WS4 with peripheral nerve and/or central nervous system involvement, namely peripheral demyelinating neuropathy, central dysmyelinating leukodystrophy, WS, and Hirschsprung’s disease or PCW/PCWH. We characterized the genetic defects underlying WS2, WS4, and the WS4-PCW/PCWH) using Sanger and whole-exome sequencing and cytogenomic microarray in seven patients from six unrelated families, including two with WS2 and five with WS4. We also performed multiple functional studies and analyzed genotype–phenotype correlations. The cohort included a relatively high frequency (80%) of individuals with neurological variants of WS4. Six novel SOX10 mutations were identified, including c.89C > A (p.Ser30^∗), c.207_8 delCG (p.Cys71Hisfs^∗62), c.479T > C (p.Leu160Pro), c.1379 delA (p.Tyr460Leufs^∗42), c.425G > C (p.Trp142Ser), and a 20-nucleotide insertion, c.1155_1174dupGCCCCACTATGGCTCAGCCT (p.Phe392Cysfs^∗117). All pathogenic variants were de novo. The results of reporter assays, western blotting, immunofluorescence, and molecular modeling supported the deleterious effects of the identified mutations and their correlations with phenotypic severity. The prediction of genotype–phenotype correlation and functional pathology, and dominant negative effect vs. haploinsufficiency in SOX10-related WS were influenced not only by site (first two vs. last coding exons) and type of mutation (missense vs. truncation/frameshift), but also by the protein expression level, molecular weight, and amino acid content of the altered protein. This in vitro analysis of SOX10 mutations thus provides a deeper understanding of the mechanisms resulting in specific WS subtypes and allows better prediction of the phenotypic manifestations, though it may not be always applicable to in vivo findings without further investigations.

Bleeding Disorders Associated with Abnormal Platelets: Glanzmann Thrombasthenia and Bernard-Soulier Syndrome

Platelets, the smallest cells in the blood, are associated with hemostasis, bowel formation, tissue remodeling, and wound healing. Although the prevalence of inherited platelet disorders is not fully known, it is a rare disease group and is encountered in approximately between 10000 and 1000000. Glanzmann thrombasthenia (GT) and Bernard-Soulier syndrome (BSS) are more frequently observed in inherited platelet disorders. In GT, the platelet aggregation stage due to deficiency or dysfunction of the platelet GPIIb/IIIa complex cannot take place. BSS is a platelet adhesion disorder due to the absence or abnormality of GPIb/IX complex on the platelet surface. If there is bleeding after easy bruising, mucous and oral cavities, menorrhagia, tooth extraction, tonsillectomy, or other surgical interventions, inherited platelet dysfunction should be considered if the platelet count is normal while the bleeding time is long. Firstly, other causes should be investigated by making differential diagnosis of GT and BSS. In this chapter, the definition, etiology, historical process, epidemiology, genetic basis, pathophysiology, clinical findings, diagnosis, differential diagnosis, and the follow-up and treatment approach of GT and BSS will be reviewed according to the current medical literature.

Molecular Aspects of Pathophysiology of Platelet Receptors

Receptor is a dynamic instrumental surface protein that helps to interact with specific molecules to respond accordingly. Platelet is the smallest in size among the blood components, but it plays many pivotal roles to maintain hemostasis involving its surface receptors. It (platelet) has cell adhesion receptors (e.g., integrins and glycoproteins), leucine-rich repeats receptors (e.g., TLRs, glycoprotein complex, and MMPs), selectins (e.g., CLEC, P-selectin, and CD), tetraspanins (e.g., CD and LAMP), transmembrane receptors (e.g., purinergic—P2Y and P2X1), prostaglandin receptors (e.g., TxA2, PGH2, and PGI2), immunoglobulin superfamily receptors (e.g., FcRγ and FcεR), etc. on its surface. The platelet receptors (e.g., glycoproteins, protease-activated receptors, and GPCRs) during platelet activation are over expressed and their granule contents are secreted (including neurotransmitters, cytokines, and chemokines) into circulation, which are found to be correlated with different physiological conditions. Interestingly, platelets promote metastasis through circulation protecting from cytolysis and endogenous immune surveillance involving several platelets receptors. The updated knowledge about different types of platelet receptors in all probable aspects, including their inter- and intra-signaling mechanisms, are discussed with respect to not only its (platelets) receptor type but also under different pathophysiological conditions.

A Comprehensive Review of Congenital Platelet Disorders, Thrombocytopenias and Thrombocytopathies

Platelets play an important role in hemostasis through platelet plug formation by a phenomenon of adhesion; activation; secretion and aggregation. Defects in platelet hemostatic mechanisms can be congenital or acquired. Congenital platelet disorders are rare and manifestations range from asymptomatic to sometimes severe bleeding. The disorders arise due to diverse mechanisms. Congenital platelet disorders include thrombocytopathies and thrombocytopenia (platelet count <150 x 10⁹/L) or thrombocytosis (platelet count > 450 x 10⁹/L). Congenital thrombocytopathies include disorders of adhesion like von Willebrand's disease or Bernard-Soulier syndrome. The disorders of aggregation include congenital afibrinogenemia and Glanzmann thrombasthenia. Disorders of storage granules are gray platelet syndrome and Quebec platelet disorder. Congenital thrombocythopathy and thrombocytopenia often occur in conjunction. In this article, we have a detailed literature review of these rare thrombocytopathies, their presentation and treatment.

Disease Burden in Patients with Glanzmann's Thrombasthenia: Perspectives from the Glanzmann's Thrombasthenia Patient/Caregiver Questionnaire

Purpose

Glanzmann’s thrombasthenia (GT) is a rare bleeding disorder caused by a mutation in the αIIbβ3 integrin essential for optimal platelet function and hemostasis. The aim of this study was to identify the burden of GT on patients and caregivers through better understanding of the management and psychosocial impact of this disorder.

Patients and Methods

Participants for this online survey were recruited using a rare disease specialty recruiter from Comprehensive Health Education Services. Data were collected from January 31 through March 12, 2019. The questionnaire was designed to collect information regarding demographics, diagnosis, treatment, and psychosocial impact.

Results

Of the 45 respondents (24 patients and 21 caregivers), the majority were female (58%), white (64%), and employed full-time (53%) and had no family history of GT (64%). Many patients reported significant bruising at birth (76%), and the mean age at diagnosis was 2.6 years. About half of the patients experienced 1 bleed per day, and 13% had over 500 bleeds of any severity per year. Most bleeds were skin bruising or mouth bleeds, but patients also reported joint/muscle and gastrointestinal bleeds. Most patients reported receiving a platelet transfusion (82%), and some had developed platelet refractoriness (38%) or antibodies (32%). Common treatments were antifibrinolytics (82%) and recombinant activated factor VII (rFVIIa) (42%), likely due to the presence of antibodies. Many (58%) patients experienced issues with excessive bleeding at school; 38% reported missing school as a result. Female patients struggled to find a gynecologist with knowledge of the management of GT. Most patients were satisfied with the support they receive from their current partner (65%) and their friends (76%).

Conclusion

Most patients with GT are diagnosed early. Patients experience considerable psychosocial impact. Patient and physician education concerning treatment alternatives and the support of the GT community are critical.

Glanzmann's Thrombasthenia: How Listening to the Patient Is Sometimes the Simple Key to Good Medicine!

Introduction. Glanzmann's thrombasthenia is a rare clotting disorder caused by impaired platelet function. Lack of awareness of the appropriate management of rare medical conditions may lead to patient dissatisfaction and potentially poor treatment outcome. Case Report. A 78-year-old male with a history of Glanzmann's thrombasthenia was admitted to the trauma service following a fall in which he sustained a facial laceration as well as maxillary sinus and nasal fractures. He received DDAVP 20 mcg and tranexamic acid upon presentation to the emergency department (ED). In the ED, the patient requested administration of platelet transfusion but was refused due to a normal platelet count. During the course of his hospital stay, he complained of epistaxis and was noted to have a downtrending hemoglobin from 11.0 g/dl to 9.0 g/dl. The patient and his family were not comfortable when the discharge plan was finalized and demanded platelet transfusion (due to history of needing platelets in association with injuries or procedures in the past) was refused by the primary team as they continued to state that his platelet count is normal. On hospital day 3, hematology was consulted as the patient and his family were extremely angry and hematology recommended platelet transfusion. Further clinical information was not available as the patient was transferred to another facility per family request as they wanted to be at a center which had the patient's primary hematologist. Discussion. A delay in specialist consultation resulted in patient dissatisfaction and extended the length of stay. Patients with rare medical conditions and potential for major complications should be managed aggressively with appropriate specialist consultation to promote patient satisfaction and improve the overall quality of care. This case shows that as physicians it our duty to listen to our patient's concerns and involve them in the medical decision-making to provide optimal patient-centered care.

Two homozygous missense mutations in ITGB3 gene as a cause of Glanzmann Thrombasthenia in four consanguineous Pakistani pedigrees

INTRODUCTION

Glanzmann thrombasthenia (GT) is most common of inherited platelet disorders, resulting from quantitative/qualitative defects in platelet surface integrin αIIbβ3, encoded by ITGA2B and ITGB3 genes. Little is known about clinical and molecular characteristics of GT patients from highly consanguineous Pakistani population.

METHODS

This study analyzed the clinical and molecular spectrum of six GT patients from four unrelated but consanguineous families. Platelet surface expression of αIIbβ3 integrin was determined using flow cytometry analysis. ITGA2B and ITGB3 genes were screened for causative mutations by DNA sequencing. Detected mutations were characterized for their pathogenicity using a variety of in silico tools.

RESULTS

Glanzmann thrombasthenia patients in this study generally presented early in life, had a severe course of clinical disease with transfusion dependency for management of bleeding episodes. Molecular analysis revealed 2 homozygous missense mutations in ITGB3 gene, c.422 A˃G (p.Y141C) in three GT patients from a single pedigree with familial segregation and c.1641 C>G (p.C547W) in three unrelated GT patients from three families manifesting type I GT with severe reduction in platelet αIIbβ3 levels. In silico pathogenicity predictions, multiple sequence alignment and 3D protein modeling unanimously suggested deleterious nature of the detected mutations, possibly due to aberrant disulfide bonding. Of note, clinical diversity was observed even among GT patients with same mutation in GT1 family.

CONCLUSION

This study provides an initial yet important account of clinical and genetic characterization of GT in local patients which may spark further studies to help molecular diagnosis, optimal disease management, and genetic counseling based prevention efforts.

Glanzmann's thrombasthenia: a rare bleeding disorder in a Nigerian girl

INTRODUCTION

Glanzmann's Thrombasthenia (GT) is a rare autosomal recessive bleeding disorder due to defective platelet membrane glycoprotein GP IIb/IIIa (integrin αIIbβ3). The prevalence is estimated at 1:1,000,000 and it is commonly seen in areas where consanguinity is high.

CASE PRESENTATION

The authors report a 12 year old Nigerian girl of Igbo ethnic group, born of non-consanguineous parents, who presented with prolonged heavy menstrual bleeding which started at menarche 3 months earlier, weakness and dizziness. She had a past history of recurrent episodes of prolonged epistaxis, gastrointestinal bleeding and gum bleeding during early childhood. On examination, she was severely pale with a haemic murmur and vaginal bleeding. The initial diagnosis was menorrhagia secondary to bleeding diathesis possibly von Willebrand's Disease. She was on supportive treatment with fresh whole blood, fresh frozen plasma and platelets until diagnosis of GT was made in the USA. Currently, she is on 3 monthly intramuscular Depo-provera with remarkable improvement.

CONCLUSION

To the best of our knowledge, this is the first documented report of GT in our environment where consanguinity is rarely practised. Our health facilities require adequate diagnostic and treatment facilities for rare diseases like GT.

Strengths and Weaknesses of Light Transmission Aggregometry in Diagnosing Hereditary Platelet Function Disorders

Hereditary defects in platelet function are responsible for sometimes severe mucocutaneous hemorrhages. They are a heterogeneous group of abnormalities whose first-line diagnosis typically involves interpreting the results of in vitro light transmission aggregometry (LTA) traces. Interpretation of LTA is challenging. LTA is usually performed in specialized laboratories with expertise in platelet pathophysiology. This review updates knowledge on LTA, describing the various platelet aggregation profiles typical of hereditary platelet disorders to guide the physician in the diagnosis of functional platelet disorders.

Glanzmann thrombasthenia: genetic basis and clinical correlates

Glanzmann thrombasthenia (GT) is an autosomal recessive disorder of platelet aggregation caused by quantitative or qualitative defects in integrins αIIb and β3. These integrins are encoded by the ITGA2B and ITGB3 genes and form platelet glycoprotein (GP)IIb/IIIa, which acts as the principal platelet receptor for fibrinogen. Although there is variability in the clinical phenotype, most patients present with severe mucocutaneous bleeding at an early age. A classic pattern of abnormal platelet aggregation, platelet glycoprotein expression and molecular studies confirm the diagnosis. Management of bleeding is based on a combination of hemostatic agents including recombinant activated factor VII with or without platelet transfusions and antifibrinolytic agents. Refractory bleeding and platelet alloimmunization are common complications. In addition, pregnant patients pose unique management challenges. This review highlights clinical and molecular aspects in the approach to patients with GT, with particular emphasis on the significance of multidisciplinary care.

Glanzmann's thrombasthenia with spontaneous upper gastrointestinal bleeding: a case report

Glanzmann’s thrombasthenia (GT) is a rare bleeding disorder inherited in an autosomal recessive manner. The pathogenesis of GT mainly involves structural abnormalities and dysfunction of platelet membrane glycoprotein IIb/IIIa (integrin αIIbβ3). The most common symptoms of GT are various types of bleeding, including recurrent nasal bleeding, mucocutaneous bleeding, unremitting bleeding after injury or operation, and menorrhea in women. Such hemorrhage may be fatal in some patients. GT with spontaneous upper gastrointestinal bleeding is relatively rare. In the present report, we describe a middle-aged man who was hospitalized with spontaneous upper gastrointestinal bleeding. His main symptom was recurrent chronic and intermittent melena. Gastroscopy revealed oozing of blood in the gastric antrum wall. However, no obvious lesions such as erosion or ulceration were found. Upon further inspection, we found that the patient’s platelet aggregation was poor, and flow cytometry assay revealed low expression of platelet membrane integrin αIIbβ3. The patient was eventually diagnosed with GT and exhibited clinical improvement after active treatment.

Lessons Learned: Deformity Correction and Tibiotalocalcaneal Arthrodesis in a Patient With Glanzmann Thrombasthenia: A Case Report

CASE

A 33-year-old woman with Glanzmann thrombasthenia presented to us with a distal tibia nonunion. We attempted to treat her with a multiplanar ring external fixator, but the patient was unable to tolerate the correction, so we resorted to a tibiotalocalcaneal fusion. Hemostasis was difficult to achieve despite the use of antithrombinolytics, factor VII, and platelet transfusions.

CONCLUSION

Bleeding can be difficult to control in patients with Glanzmann thrombasthenia. However, overaggressive preadministration of antithrombinolytics should be avoided because it may have adverse effects such as acrocyanosis. The presence of thrombasthenia does not seem to affect the success of arthrodesis.

The Extracellular Matrix: An Accomplice in Gastric Cancer Development and Progression

The extracellular matrix (ECM) is a dynamic and highly organized tissue structure, providing support and maintaining normal epithelial architecture. In the last decade, increasing evidence has emerged demonstrating that alterations in ECM composition and assembly strongly affect cellular function and behavior. Even though the detailed mechanisms underlying cell-ECM crosstalk are yet to unravel, it is well established that ECM deregulation accompanies the development of many pathological conditions, such as gastric cancer. Notably, gastric cancer remains a worldwide concern, representing the third most frequent cause of cancer-associated deaths. Despite increased surveillance protocols, patients are usually diagnosed at advanced disease stages, urging the identification of novel diagnostic biomarkers and efficient therapeutic strategies. In this review, we provide a comprehensive overview regarding expression patterns of ECM components and cognate receptors described in normal gastric epithelium, pre-malignant lesions, and gastric carcinomas. Important insights are also discussed for the use of ECM-associated molecules as predictive biomarkers of the disease or as potential targets in gastric cancer.