Glanzmann thrombasthenia: genetic basis and clinical correlates

Management of a twin pregnancy patient with Glanzmann thrombasthenia might be caused by a novel ITGA2B gene mutation (c.2822G>A): a case report and family investigation

Mutations in the ITGA2B or ITGB3 gene that encodes for the αIIbβ3 platelet integrin usually cause Glanzmann thrombasthenia (GT). This study aims to investigate the clinical characteristics of a pedigree exhibiting an inherited hemorrhagic disorder resembling GT, elucidate its molecular pathogenesis and evaluate the efficacy of blood management strategies for a proband who is pregnant with twins. The clinical data of the pedigree with inherited hemorrhagic disorder were collected, including the assessment of clinical, laboratory and thromboelastography (TEG) profiles. DNA samples were obtained for next-generation sequencing, encompassing the exons and flanking sequences of the ITGA2B and ITGB3 genes, as well as other genes associated with blood and immune deficiency. Bioinformatics software tools, such as PolyPhen-2, SIFT and MutationTaster, were employed to analyze the functional impact of mutations. Protein structural models for the new mutation type were generated using PyMOL. The phenotype of the proband in this pedigree with inherited platelet dysfunction and bleeding disorder was in accordance with GT. The proband shows persistent blood accumulation in the uterine cavity. Laboratory findings indicate normal PLT morphology, PLT count, MPV, and PDW. However, there is a decreased PLT aggregation induced by agonists ADP, collagen, and AA while maintaining a normal response to ristocetin. The initial TEG examination results indicated that the patient presented with a hypocoagulable state, characterize d by a reduction in α angle (46.9), an extended K value (4.6) and a decreased maximum amplitude (35.1). The younger sister demonstrated comparable TEG performance to that of the proband and has a documented history of abnormal bleeding. A novel heterozygous mutation of ITGA2B at position c.2822 G>A (p.Trp941*) was identified in the proband and her familial counterparts-father, brother and sister. MutationTaster software predicted the new mutation to be pathogenic; however, PolyPhen-2 and SIFT software did not provide correlated predictions. The p.Trp941* mutation resulted in the premature termination of translation at residue 940Trp, leading to impaired protein function. Successful management was achieved during the perioperative period by administration of human immunoglobulin, platelets and antifibrinolytic drugs, followed by recombinant factor VIIa (rFVIIa), according to the thromboelastography tracings. The laboratory findings of the proband are consistent with GT, and a novel mutation in the ITGA2B gene at position c.2822 G>A (p.Trp941*) has been identified as a potential cause of GT. However, since GT is a recessive disorder and both the proband and her family members are heterozygous, it cannot be excluded that they may possess additional bleeding risk factors, including the presence of other undetected variants. This study also illustrates the significance of multidisciplinary planning, TEG analysis and judicious utilization of rFVIIa to minimize operative bleeding risk.

Glanzmann thrombasthenia: a multi-center study of demographics, clinical spectrum, and treatment efficacy

Glanzmann thrombasthenia (GT) is a rare inherited bleeding disorder caused by quantitative or qualitative defects of platelet integrin GPIIb/IIIa (CD41 and CD61). This study intended to describe the demographics, clinical features, and treatment response of GT patients in several hematology centers in Egypt. A cross-sectional multi-center study involved 87 children (<18 years old) diagnosed with GT. Clinical data were recorded as bleeding manifestations, response to treatment modalities, and laboratory results. The study included eighty-seven children (61 females and 26 males) with a median age of 8 years. Sixty-one children (55.2%) were born to parents who were consanguineous. The median age at presentation was 3 years (birth-14 years). The most frequent initial presenting symptom was epistaxis (39.1%), followed by cutaneous bleeding (29.9%), gastrointestinal bleeding (23%), heavy menstrual bleeding (19.5%), bleeding per gum (10.3%), and post-circumcision bleeding (5.7%), while one patient initially presented with intracranial hemorrhage (1.1%). These also constituted common bleeding sites. Eighty children (92%) received treatment. Platelet transfusions were given to 65 patients, with a response rate of 73.8%, and recombinant factor VII concentrates were given to 71 patients, with a response rate of 90.1%. Type I GT represented most of our patients (79.3%), followed by type III (11.5%) and type II (9.2%). No significant correlation was found between CD41/CD61 expression and other parameters as the patient's age, bleeding frequency, and treatment response. There was no evident difference between the three forms of GT regarding clinical characteristics such as bleeding severity or response to treatment. What is known: • Glanzmann thrombasthenia is the most common inherited platelet function abnormality. • Treatment is based on general supportive measures, platelet transfusion and recombinant factor VIIa. What is new: • Glanzmann thrombasthenia is an underestimated disorder, with a significant delay in diagnosis. • Although it has three types, there is no significant variation in bleeding phenotype between them.

Novel homozygous frameshift mutation of ITGB3 in the Glanzmann thrombasthenia patient with abnormal bone metabolism and congenital bone defects

BACKGROUND

Glanzmann thrombasthenia (GT) is a rare inherited bleeding disorder caused by dysfunction of the integrin αIIbβ3 in platelets. The subunit β3, encoded by ITGB3 also plays a significant role in bone metabolism. Whether GT patients with β3 deficiency also suffer from bone pathology remains unclear.

METHOD

The 21-year-old female patient presenting with bleeding diathesis and multiple congenital bone defects in her right hand, and her seven family members were included in the study. Whole exome sequencing as well as Sanger sequencing were conducted to identify GT-associated mutations within the family. The platelet function of the family was detected by the platelet aggregation test and thromboelastography (TEG). The expression levels of CD41 (αIIb) and CD61 (β3) on the platelet surface and total in platelet were detected by flow cytometry and Western blot. Bioinformatics analysis was used to evaluate the pathogenicity of mutation sites and their effects on protein structure and function. X-ray imaging, bone densitometry and bone metabolism index were performed to evaluate bone development and metabolism.

RESULT

A novel homozygous frameshift mutation c.2143_2158delinsCT (p.Lys715Leufs*36) of ITGB3 was found in the proband. Platelet aggregation by ADP, collagen, epinephrine, and arachidonic acid was absent, TEG showed hypocoagulability and decreased platelet function, and the expression levels of αIIb and β3 on the platelet surface and total in platelet were significantly reduced (< 5%) in the proband. The parents, second elder sister and grandmother of proband were heterozygous carriers without bleeding symptoms and had normal platelet aggregation function and αIIb/β3 protein expression. Structural modeling strongly suggested that the mutation creates a truncation in cytoplasmic domains of β3, resulting in the mutant β3/αIIbβ3 inactivated and low expression. The proband was born with partial absence of phalanges in digits 2-4 and the deformity of fingers 1 and 5 in her right hand, bone densitometry indicated significant osteopenia and increased risk of fracture in her right radius, and no other gene mutations related to bone pathology were identified.

CONCLUSION

A novel mutation of ITGB3 which results in GT was identified. This is the third reported case of GT combined with bone defect. Our work expands ITGB3 mutation spectrum and provide further insights into the potential association between GT and bone development and metabolism.

Management challenge of a rare concomitant platelet glycoprotein IV/CD36 and IIb/IIIa deficiencies: Case illustration

INTRODUCTION/BACKGROUND

Platelet membrane glycoproteins (GPs) serve several functions, the most significant of which is their role in primary hemostasis. Among these, GP IIb/IIIa is the primary fibrinogen receptor and is essential for platelet aggregation. Its deficiency or dysfunction impairs platelet aggregation, leading to Glanzmann thrombasthenia, a rare autosomal recessive bleeding disorder. In contrast, platelet GP IV (CD36) has a limited role in primary hemostasis. While also rare, CD36 deficiency has a disproportionately higher prevalence in individuals of East Asian, African, and Arabian descent. Patients with platelet GP deficiencies can develop antibodies against the missing GPs, leading to immune-mediated platelet transfusion refractoriness (PTR). Consequently, they are unresponsive to platelet transfusions when mostly needed.

CASE PRESENTATION

Here we present the case of an Egyptian male with a lifelong history of an incompletely characterized bleeding disorder who presented for pre-surgical evaluation. We diagnosed the patient with Type I Glanzmann thrombasthenia. Further evaluation revealed anti-CD36 antibodies, leading to the discovery of a concurrent platelet CD36 deficiency. The dual GP deficiency significantly complicated his management, as finding crossmatch-compatible platelets was challenging due to the rarity of CD36-deficient blood donors in the United States.

DISCUSSION/CONCLUSION

Awareness of coexisting platelet disorders and their ramifications is limited, mostly because these are stochastically rare (~1 in 100 million for the present case). This case highlights the importance of thoroughly evaluating platelet glycoprotein deficiencies, particularly in individuals with severe bleeding disorders and from ethnic backgrounds with a predisposition to specific platelet disorders. Such an approach can prevent future platelet antibody formation or reduce bleeding risk with pre-existing antibodies.

Obstetric and Gynaecological Challenges and Outcomes in Women and Girls With Glanzmann's Thrombasthenia

INTRODUCTION

Glanzmann's thrombasthenia (GT) is an inherited platelet function disorder that may manifest with significant bleeding symptoms; in women and girls (W&Gs), heavy menstrual bleeding (HMB) is very common. GT in pregnancy is associated with an increased risk of postpartum haemorrhage (PPH).

AIM

This study highlights the gynaecological and obstetric challenges experienced by W&Gs with GT, and reviews available treatment options.

METHODS

Data regarding 38 W&Gs with GT were analysed from the ISTH REDCap registry, an international multi-centre database.

RESULTS

Among 38 W&Gs, 76% of Middle Eastern ethnicity, 100% reported HMB; 92% HMB since menarche, and 82% presented with acute HMB and were treated with platelets and packed red blood cells (pRBCs) transfusions in addition to hormonal therapies. Management of chronic HMB required a combination therapy including antifibrinolytics (tranexamic acid [TXA]), hormonal therapies, and recombinant factor VIIa (rFVIIa); rFVIIa was used in 50% of W&Gs. In 16 pregnancies, PPH was reported in 63% of deliveries, of which 83% required blood and platelet transfusions. Despite prophylactic haemostatic agents during labour and delivery in 8/9 pregnancies of women with known GT diagnosis, 78% experienced PPH. Thirty-one percent of neonates developed neonatal alloimmune thrombocytopenia (NAIT).

CONCLUSION

HMB and PPH are common bleeding complications in GT. Effective management of HMB and PPH in W&Gs with GT is challenging but can be achieved by a multidisciplinary team, often requiring a combination of haemostatic agents with hormonal therapies. Use of rFVIIa may limit the need for platelet transfusion, thus reducing alloimmunisation and the risk of developing NAIT.

Insights for variant clinical interpretation based on a benchmark of 65 variant effect predictors

Single amino acid substitutions in protein sequences are generally harmless, but a certain number of these changes can lead to disease. Accurately predicting the effect of genetic variants is crucial for clinicians as it accelerates the diagnosis of patients with missense variants associated with health problems. Many computational tools have been developed to predict the pathogenicity of genetic variants with various approaches. Analysing the performance of these different computational tools is crucial to provide guidance to both future users and especially clinicians. In this study, a large-scale investigation of 65 tools was conducted. Variants from both clinical and functional contexts were used, incorporating data from the ClinVar database and bibliographic sources. The analysis showed that AlphaMissense often performed very well and was in fact one of the best options among the existing tools. In addition, as expected, meta-predictors perform well on average. Tools using evolutionary information showed the best performance for functional variants. These results also highlighted some heterogeneity in the difficulty of predicting some specific variants while others are always well categorized. Strikingly, the majority of variants from the ClinVar database appear to be easy to predict, while variants from other sources of data are more challenging. This raises questions about the use of ClinVar and the dataset used to validate tools accuracy. In addition, these results show that this variant predictability can be divided into three distinct classes: easy, moderate and hard to predict. We analyzed the parameters leading to these differences and showed that the classes are related to structural and functional information.

The Role of Platelet Dysfunctions in the Pathogenesis of the Hemostatic-Coagulant System Imbalances

Platelet dysfunction plays a critical role in the pathogenesis of various disorders affecting the hemostatic-coagulant system. This review aims to explore the mechanisms by which platelet dysfunctions contribute to the disruption of hemostasis, leading to an increased risk of both thrombosis and bleeding. Platelets, traditionally known for their role in clot formation, can exhibit altered functionality under pathological conditions such as cardiovascular diseases, metabolic disorders, and autoimmune diseases, impacting their interaction with coagulation factors and vascular endothelium. The review discusses the molecular and cellular mechanisms underlying platelet dysfunction, including aberrations in platelet activation, aggregation, and secretion. It also highlights the interplay between platelets and other components of the coagulation cascade, such as fibrinogen and clotting factors, in maintaining vascular integrity. Moreover, the review examines clinical implications, including how platelet dysfunction can be a contributing factor in conditions like deep vein thrombosis, stroke, and disseminated intravascular coagulation (DIC). Finally, current therapeutic approaches targeting platelet dysfunctions, including antiplatelet agents and emerging therapies, are reviewed to provide insights into potential strategies for managing fluid-coagulation system imbalances. This review underscores the importance of a comprehensive understanding of platelet dysfunction to improve diagnosis and treatment of hemostatic disorders.

Glanzmann Thrombasthenia 10 Years Later: Progress Made and Future Directions

Glanzmann thrombasthenia (GT) is the most common inherited platelet disorder (IPD) with mucocutaneous bleeding and a failure of platelets to aggregate when stimulated. The molecular cause is insufficient or defective αIIbβ3, an integrin encoded by the ITGA2B and ITGB3 genes. On activation αIIbβ3 undergoes conformational changes and binds fibrinogen (Fg) and other proteins to join platelets in the aggregate. The application of next-generation sequencing (NGS) to patients with IPDs has accelerated genotyping for GT; progress accompanied by improved mutation curation. The evaluation by NGS of variants in other hemostasis and vascular genes is a major step toward understanding why bleeding varies so much between patients. The recently discovered role for glycoprotein VI in thrombus formation, through its binding to fibrin and surface-bound Fg, may offer a mechanosensitive back-up for αIIbβ3, especially at sites of inflammation. The setting up of national networks for IPDs and GT is improving patient care. Hematopoietic stem cell therapy provides a long-term cure for severe cases; however, prophylaxis by monoclonal antibodies designed to accelerate fibrin formation at injured sites in the vasculature is a promising development. Gene therapy using lentil-virus vectors remains a future option with CRISPR/Cas9 technologies offering a promising alternative route.

Epidemiological and clinical characteristics of children and young adults with Glanzmann's thrombasthenia in upper Egypt: a multicenter cross-sectional study

BACKGROUND

Glanzmann's thrombasthenia (GT) is an inherited rare bleeding disorder characterized by a deficiency or functional defect in the platelet αIIbβ3 integrin. This impairs normal platelet aggregation and leads to prolonged and spontaneous mucocutaneous bleeds.

OBJECTIVES

To report disease characteristics of a GT cohort from five tertiary hospitals in Upper Egypt.

MATERIALS AND METHODS

We conducted a retrospective cross-sectional observational study, relying on patients' medical records and interview surveys to collect information from patients diagnosed with congenital GT between October 2023 and April 2024.

RESULTS

We recruited 131 people with GT (PwGT) of different ages, mainly children and adolescents. 73.3% of the study cohort had type I GT, 23.7% had type II GT, and 3% had type III GT. Consanguinity and family history were prevalent in our cohort, with an expected prevalence of more than one per 200,000 in our region. The median value of ADP aggregation was 8%. In type I GT, the median levels of CD41 and CD61 were 0.3%. In contrast, type II GT had median levels of 12% for CD41 and 17% for CD61. The most frequent manifestations were epistaxis (77.1%), subcutaneous bleeds (40.5%), menorrhagia (22.1%), and mucosal bleeds (18.3%). 72.5% of PwGT used rFVIIa and 69.5% used platelet transfusions to treat acute and surgical bleeds, while only 6.9% used tranexamic acid as monotherapy.

CONCLUSION

Estimating the actual burden of GT in Egypt requires accurate diagnoses, as well as systematic and standardized data collection. The rooted consanguinity pattern in Upper Egypt contributes to a higher prevalence of GT above the country's average.

The Diagnostic Assessment of Platelet Function Defects - Part 2: Update on Platelet Disorders

Congenital platelet disorders are rare and targeted treatment is usually not possible. Inherited platelet function disorders (iPFDs) can affect surface receptors and multiple platelet responses such as defects of platelet granules, signal transduction, and procoagulant activity. If iPFDs are also associated with a reduced platelet count (thrombocytopenia), it is not uncommon to be misdiagnosed as immune thrombocytopenia. Because the bleeding tendency of the different platelet disorders is variable, a correct diagnosis of the platelet defect based on phenotyping, function analysis, and genotyping is essential, especially in the perioperative setting. In the case of a platelet receptor deficiency, such as Bernard-Soulier syndrome or Glanzmann thrombasthenia, not only the bleeding tendency but also the risk of isoimmunization after platelet transfusions or pregnancy has to be considered. Platelet granule disorders are commonly associated with either intrinsically quantitative or qualitative granule defects due to impaired granulopoiesis, or granule release defects, which can also affect additional signaling pathways. Functional platelet defects require expertise in the clinical bleeding tendency in terms of the disorder when using antiplatelet agents or other medications that affect platelet function. Platelet defects associated with hematological-oncological diseases require comprehensive information about the patient including the clinical implication of the genetic testing. This review focuses on genetics, clinical presentation, and laboratory platelet function analysis of iPFDs with or without reduced platelet number. As platelet defects affecting the cytoskeleton usually show thrombocytopenia, but less impaired or normal platelet functional responses, they are not specifically addressed.

The Diagnostic Assessment of Inherited Platelet Function Defects - Part 1: An Overview of the Diagnostic Approach and Laboratory Methods

In this article, our goal is to offer an introduction and overview of the diagnostic approach to inherited platelet function defects (iPFDs) for clinicians and laboratory personnel who are beginning to engage in the field. We describe the most commonly used laboratory methods and propose a diagnostic four-step approach, wherein each stage requires a higher level of expertise and more specialized methods. It should be noted that our proposed approach differs from the ISTH Guidance on this topic in some points. The first step in the diagnostic approach of iPFD should be a thorough medical history and clinical examination. We strongly advocate for the use of a validated bleeding score like the ISTH-BAT (International Society on Thrombosis and Haemostasis Bleeding Assessment Tool). External factors like diet and medication have to be considered. The second step should rule out plasmatic bleeding disorders and von Willebrand disease. Once this has been accomplished, the third step consists of a thorough platelet investigation of platelet phenotype and function. Established methods consist of blood smear analysis by light microscopy, light transmission aggregometry, and flow cytometry. Additional techniques such as lumiaggregometry, immune fluorescence microscopy, and platelet-dependent thrombin generation help confirm and specify the diagnosis of iPFD. In the fourth and last step, genetic testing can confirm a diagnosis, reveal novel mutations, and allow to compare unclear genetics with lab results. If diagnosis cannot be established through this process, experimental methods such as electron microscopy can give insight into the underlying disease.

Glanzmann Thrombasthenia in a Newborn Due to a Rare Homozygous Missense Mutation

Glanzmann thrombasthenia (GT) is an autosomal recessive platelet functional bleeding disorder caused by mutations in the ITGA2B or ITGB3 genes, often presenting as mucocutaneous bleeding. GT typically presents in infancy, but this study reports a rare case of neonatal presentation in a female infant born to consanguineous parents. The mother, a 27-year-old woman with a family history of GT, presented at 36 weeks gestation for an elective cesarean due to a breech presentation. The newborn, delivered with an appearance, pulse, grimace, activity, and respiration (APGAR) score of 9, exhibited spontaneous bruising, gum bleeding, and hyperbilirubinemia, necessitating neonatal intensive care admission. An initial hematologic workup showed normal coagulation profiles, but platelet function was significantly impaired. Genetic analysis identified a homozygous ITGB3 mutation, p.Asp145Asn, with both parents confirmed as heterozygous carriers. Management included factor VIIa, platelet transfusions, fresh frozen plasma, and RBCs. This case underscores the critical need for early recognition of GT in neonates with severe bleeding, especially with family history and consanguinity, and highlights the implications of the p.Asp145Asn mutation in the severe neonatal presentation. Genetic counseling is recommended for the family given the 25% recurrence risk in future pregnancies, and prospective partner testing may aid in assessing recurrence risks for descendants.

Bleeding Phenotype of Glanzmann Thrombasthenia (GT) and Treatment Outcomes in Over One Hundred Patients: A Two-Center Experience in North Pakistan

BACKGROUND

Glanzmann thrombasthenia (GT) is a rare disease with an autosomal recessive inheritance pattern. This disorder is not so uncommonly encountered in routine clinical practice and laboratory settings in Pakistan let alone in the rest of the world. To describe the bleeding phenotype of GT and treatment outcomes in over one hundred patients in north Pakistan.

MATERIALS AND METHODS

This descriptive, cross-sectional, retrospective study was conducted on patients from 2011 to 2023 using a convenience sampling technique. A total of 103 patients of all ages and both genders diagnosed as having inherited GT were included in the study.

RESULTS

The median age of the study population was 1.1 years, with an interquartile range (IQR) of 0.8-2. Out of the total, 55 (53%) patients were males and 48 (47%) patients were females. Ninety-eight percent of patients were diagnosed using light transmission aggregometry, and only two (2%) patients were diagnosed by immunophenotyping. Due to the high incidence of interfamily marriages, 86 (84%) patients were born to consanguineous marriages. Thirty-nine (38%) patients had an episode of major bleeding as defined by the International Society on Thrombosis and Haemostasis (ISTH) criteria. Epistaxis in 73 (71%) patients, skin bruising in 63 (61%), and gum bleeding in 57 (55%) were the most common bleeding symptoms. Thirty-two (31%) required the use of r-VIIa for major bleeding and five (5%) patients underwent fully matched allogeneic HSCT (hematopoietic stem cell transplant). Graft versus host disease-free relapse-free survival (GRFS) was 80%.

CONCLUSION

GT is still an underrecognized and underdiagnosed disorder, particularly in resource-limited settings where the estimated incidence seems to be much higher than reported.

Oral invasive procedures in Glanzmann thrombasthenia: a retrospective observational study

Background

Glanzmann thrombasthenia (GT) is a very rare autosomal inherited bleeding disease affecting megakaryocyte lineage with impacts on oral health such as gingival bleeding, which requires specific management protocols. Very few clinical cases have been published in the dental and hematologic literature.

Objectives

This study focuses on a series of 21 patients affected specifically by GT and their hemorrhagic prophylaxis management with the use of recombinant activated factor VII (rFVIIa) for dental extractions and full-mouth debridement.

Methods

Data were collected from medical and dental records. rFVIIa was administered prophylactically for oral procedures, following a standardized protocol. Each sessions were performed by experienced oral surgeons, and outcomes were analyzed with a focus on bleeding complications and adverse events.

Results

Forty-one full-mouth debridements and 176 dental extractions were performed during 102 sessions of dental care in an outpatient setting. A total of 226 injections of rFVIIa was delivered. The mean number of injections was 2.2 (range, 1-4) per dental procedure. The overall rate of bleeding complications was 5.9% (n = 6). All 6 hemorrhagic complications were classified as minor bleeding. No thromboembolic event or allergic reaction was observed.

Conclusion

The data presented in this retrospective observational study support the efficacy and safety of rFVIIa for the prevention of bleeding during invasive dental procedures in patients affected by GT. The rFVIIa protocol presented here seems to be a safe and efficient protocol for the prevention of bleeding during invasive oral procedures.

Hemorrhagic cholecystitis afflicted with glanzmann thrombasthenia patient

Hemorrhagic cholecystitis is a rare and potentially life-threatening condition that requires immediate medical attention. If the gallbladder perforates, it can lead to even more severe complications. We present the case of a 27-year-old man with Glanzmann's thrombasthenia, a rare platelets disorder, who visited the emergency department twice before being diagnosed with this condition. Initially, he complained of ear pain, and later, chest pain. Despite a normal ECG and cardiac markers, he was discharged with non-steroidal anti-inflammatory drugs (NSAIDs) for musculoskeletal pain. However, when he returned with abdominal pain, nausea, and vomiting, an ultrasound revealed signs of cholecystitis. An emergency laparoscopic cholecystectomy was performed, which revealed hemorrhagic cholecystitis.

A rare case of glanzmann thrombasthenia with concomitant factor VII deficiency

Glanzmann thrombasthenia and clotting factor VII deficiency are rare autosomal recessive bleeding disorders. But the occurrence of both in the same person is an extremely rare phenomenon. Here, we present the case of a young female from Sindh, Pakistan that got diagnosed with Glanzmann thrombasthenia and concomitant moderate factor VII deficiency, a combination not previously reported in the country. The patient exhibited typical clinical manifestations including menorrhagia, nasal bleeds, and prolonged bleeding after minor injuries, compounded by a positive family history and consanguinity. Laboratory investigations revealed marked anemia, prolonged bleeding time, and abnormal platelet aggregation studies consistent with Glanzmann thrombasthenia. The identification of this rare combination relied on comprehensive clinical evaluation, emphasizing the importance of family history in suspected cases. Management involved platelet transfusions, tranexamic acid, and Factor VII replacement, resulting in clinical improvement.

Targeting tissue factor pathway inhibitor with concizumab to improve hemostasis in patients with Glanzmann thrombasthenia: an in vitro study

BACKGROUND

Glanzmann thrombasthenia (GT) is caused by an inherited defect of platelet αIIbβ3 integrin. Concizumab, a monoclonal antibody specific for tissue factor pathway inhibitor, abolishes its anticoagulant effect.

OBJECTIVES

To evaluate the in vitro ability of concizumab to improve hemostasis in GT.

METHODS

The effects of concizumab were evaluated in whole blood or platelet-rich plasma from GT patients (n = 5-9) using a thrombin generation assay, rotational thromboelastometry (ROTEM), a global fibrinolytic capacity assay, and a flow chamber assay (Total Thrombus formation Analysis System). Washed platelets (WPs) and 20 nM recombinant activated factor VII (rFVIIa) were included for comparison.

RESULTS

The lag time in the thrombin generation assay was significantly longer (+85%; P < .0001) in GT patients than in controls. WPs, rFVIIa, and concizumab each significantly improved thrombin generation profiles. The ROTEM clotting time (CT) was significantly longer in GT patients than in controls (677 seconds vs 523 seconds; P = .03). However, CT improved after adding WPs, rFVIIa, or concizumab. Under flow, occlusive thrombi were present in all healthy controls after 10 minutes, whereas platelet-fibrin depositions were not seen in GT patients. Subocclusive or occlusive thrombi formed when GT blood was mixed with WPs, rFVIIa, or concizumab. Clots in GT platelet-rich plasma were more susceptible to fibrinolysis and were improved by WPs, rFVIIa, or concizumab.

CONCLUSION

Concizumab enhanced thrombin generation, decreased the ROTEM CT, improved thrombus formation under flow, and reduced clot lysis. Our results demonstrate the potential of concizumab for subcutaneous prophylaxis in GT patients.

Current status and future perspectives of platelet-derived extracellular vesicles in cancer diagnosis and treatment

Platelets are a significant component of the cell population in the tumour microenvironment (TME). Platelets influence other immune cells and perform cross-talk with tumour cells, playing an important role in tumour development. Extracellular vesicles (EVs) are small membrane vesicles released from the cells into the TME. They can transfer biological information, including proteins, nucleic acids, and metabolites, from secretory cells to target receptor cells. This process affects the progression of various human diseases, particularly cancer. In recent years, several studies have demonstrated that platelet-derived extracellular vesicles (PEVs) can help regulate the malignant biological behaviours of tumours, including malignant proliferation, resistance to cell death, invasion and metastasis, metabolic reprogramming, immunity, and angiogenesis. Consequently, PEVs have been identified as key regulators of tumour progression. Therefore, targeting PEVs is a potential strategy for tumour treatment. Furthermore, the extensive use of nanomaterials in medical research has indicated that engineered PEVs are ideal delivery systems for therapeutic drugs. Recent studies have demonstrated that PEV engineering technologies play a pivotal role in the treatment of tumours by combining photothermal therapy, immunotherapy, and chemotherapy. In addition, aberrant changes in PEVs are closely associated with the clinicopathological features of patients with tumours, which may serve as liquid biopsy markers for early diagnosis, monitoring disease progression, and the prognostic assessment of patients with tumours. A comprehensive investigation into the role and potential mechanisms of PEVs in tumourigenesis may provide novel diagnostic biomarkers and potential therapeutic strategies for treating human tumours.

Contributions of the individual domains of αIIbβ3 integrin to its extension: Insights from multiscale modeling

The platelet integrin αIIbβ3 undergoes long-range conformational transitions between bent and extended conformations to regulate platelet aggregation during hemostasis and thrombosis. However, how exactly αIIbβ3 transitions between conformations remains largely elusive. Here, we studied how transitions across bent and extended-closed conformations of αIIbβ3 integrin are regulated by effective interactions between its functional domains. We first carried out μs-long equilibrium molecular dynamics (MD) simulations of full-length αIIbβ3 integrins in bent and intermediate conformations, the latter characterized by an extended headpiece and closed legs. Then, we built heterogeneous elastic network models, perturbed inter-domain interactions, and evaluated their relative contributions to the energy barriers between conformations. Results showed that integrin extension emerges from: (i) changes in interfaces between functional domains; (ii) allosteric coupling of the head and upper leg domains with flexible lower leg domains. Collectively, these results provide new insights into integrin conformational activation based on short- and long-range interactions between its functional domains and highlight the importance of the lower legs in the regulation of integrin allostery.

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.

The role of platelet desialylation as a biomarker in primary immune thrombocytopenia: mechanisms and therapeutic perspectives

Primary immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by the destruction of platelets. Although it was long believed that the critical role of autoantibodies in platelet destruction, primarily through the Fc-dependent platelet clearance pathway, recent findings indicate that the significance of the Fc-independent platelet clearance pathway mediated by hepatocytes, thus shedding light on a previously obscure aspect of ITP pathogenesis. Within this context, the desialylation of platelets has emerged as a pivotal biochemical marker. Consequently, targeting platelet desialylation emerges as a novel therapeutic strategy in the pathogenesis of ITP. Notably, prevailing research has largely focused on antiplatelet antibodies and the glycosylation-associated mechanisms of platelet clearance, while comprehensive analysis of platelet desialylation remains scant. In response, we retrospectively discuss the historical progression, inducing factors, generation process, and molecular regulatory mechanisms underlying platelet desialylation in ITP pathogenesis. By systematically evaluating the most recent research findings, we contribute to a comprehensive understanding of the intricate processes involved. Moreover, our manuscript delves into the potential application of desialylation regulatory strategies in ITP therapy, heralding novel therapeutic avenues. In conclusion, this manuscript not only fills a critical void in existing literature but also paves the way for future research by establishing a systematic theoretical framework. By inspiring new research ideas and offering insights into the development of new therapeutic strategies and targeted drugs, our study is poised to significantly advance the clinical management of ITP.

Platelets and Neurodegenerative Diseases: Current Knowledge and Future Perspectives

Platelets have a fundamental role in mediating hemostasis and thrombosis. However, more recently, a new idea is making headway, highlighting the importance of platelets as significant actors in modulating immune and inflammatory responses. In particular, platelets have an important role in the development of vascular amyloid-b-peptide(ab) deposits, known to play a relevant role in Alzheimer's disease (AD) through accumulation and deposition within the frontal cortex and hippocampus in the brain. The involvement of platelets in the pathogenesis of AD opens up the highly attractive possibility of applying antiplatelet therapy for the treatment and/or prevention of AD, but conclusive results are scarce. Even less is known about the potential role of platelets in mild cognitive impairment (MCI). The aim to this brief review is to summarize current knowledge on this topic and to introduce the new perspectives on the possible role of platelet activation as therapeutic target both in AD and MCI.

A novel ITGA2B double cytosine frameshift variant (c.1986_1987insCC) leads to Glanzmann's thrombasthenia in a cat

BACKGROUND

Glanzmann's thrombasthenia (GT) is a congenital platelet disorder affecting approximately 1:1 000 000 people globally and characterized by impaired platelet aggregation and clot retraction. Autosomal recessive, loss-of-function, variants in ITGA2B or ITGB3 of the αIIbβ3 receptor cause the disease in humans. A cat affected by Glanzmann's and macrothrombocytopenia was presented to the UC Davis VMTH.

HYPOTHESIS/OBJECTIVES

Severe thrombopathia in this cat has an underlying genetic etiology.

ANIMALS

A single affected patient, 2 age-matched clinically healthy controls, and a geriatric population (n = 20) of normal cats.

METHODS

Physical examination and clinical pathology tests were performed on the patient. Flow cytometry and platelet aggregometry analyses for patient phenotyping were performed. Patient and validation cohort gDNA samples were extracted for Sanger sequencing of a previously identified ITGA2B (c.1986delC) variant. Reverse transcriptase PCR was performed on patient and healthy control PRP samples to verify ITGA2B variant consequence.

RESULTS

A novel c.1986_1987insCC autosomal recessive variant in ITGA2B was identified. This variant was absent in a population of 194 unrelated cats spanning 44 different breeds. Complete loss of ITGA2B transcript and protein expression was verified by RT-PCR and flow cytometry, explaining the underlying etiology of GT, and likely macrothrombocytopenia, in this cat.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study emphasizes the role of precision medicine in cardiovascular disease of cats and identified yet another variant that may be of utility for screening in the feline population. This study provides a small-volume, standardized, successful protocol for adequate platelet RNA isolation and subsequent molecular assessment of gene expression in cats.

Should HLA and HPA-matched platelet transfusions for patients with Glanzmann Thrombasthenia or Bernard-Soulier syndrome be standardized care? A Dutch survey and recommendations

BACKGROUND

Glanzmann thrombasthenia (GT) and Bernard-Soulier syndrome (BSS) patients require frequent platelet transfusions and hence have an increased risk for alloimmunization against donor Human Leukocyte Antigens (HLA) when no HLA-matching is performed. Knowing that Human Platelet Antigens (HPA) are located on the platelet glycoproteins that can be absent in these patients, preventive HPA-matching may also be considered. Uniform recommendations on this topic lack in transfusion guidelines making standard practice unclear, therefore, we aimed to provide a framework for matched platelet transfusions.

STUDY DESIGN AND METHODS

We conducted a targeted literature search and a national survey of Dutch (pediatric) hematologists from July to September 2021.

RESULTS

We found 20 articles describing platelet transfusion policies in 483 GT-patients and 29 BSS-patients, both adults and children. Twenty surveys were returned for full analysis. All responders treated patients with platelet disorders, including GT (n = 36 reported) and BSS (n = 29 reported). Of respondents, 75% estimated the risk of antibody formation as "likely" for HLA and 65% for HPA. Formation of HLA antibodies was reported in 5 GT and in 5 BSS-patients, including one child. Fifteen respondents gave preventive HLA-matched platelets in elective setting (75%). Three respondents additionally matched for HPA in GT-patients (15%). Main argument for matched platelet transfusions was preventing alloimmunization to safeguard the effectivity of 'random' donor-platelets in acute settings.

CONCLUSION

Elective HLA-matching for GT and BSS-patients is already conducted by most Dutch (pediatric) hematologists. HPA-matching is mainly applied when HPA-antibodies are formed. Based on the current literature and the survey, recommendations are proposed.

[Pedigree Analysis and Molecular Mechanism Study of Hereditary Glanzmann Thrombasthenia Caused by Compound Heterozygous Mutation of the ITGA2B Gene]

Objective: The phenotype and genotype of a pedigree with Glanzmann thrombasthenia caused by compound heterozygous mutation in the ITGA2B gene and its molecular pathogenesis were explored. Methods: The platelet aggregation rate of the proband and his family was detected by using a platelet aggregation test with adenosine diphosphate, collagen, epinephrine, arachidonic acid, and ristocetin. The expression levels of CD41 (αⅡb), CD61 (β3), and CD42b (GPⅠb) on the platelet surface was detected by flow cytometry. Gene sequencing technology was used for the genetic identification of the family. RT-PCR was used in the detection of mRNA splicing, and qRT-PCR was used in detecting the relative mRNA level of the ITGA2B gene. Bioinformatics analysis was used to evaluate the pathogenicity of mutation sites and their effects on protein structure and function. The expressions of total αⅡb and β3 in platelets were analyzed by Western blot. Results: Except ristocetin, the other four inducers could not induce platelet aggregation in the proband. Flow cytometry showed that the expression levels of αⅡb and β3 were only 0.25% and 9.76%, respectively, on the platelet surface of the proband, whereas GPⅠb expression was relatively normal. The expression levels of glycoproteins in the other family members were almost normal. c.480C>G and c.2929C>T mutations were detected in the proband through gene sequencing. The c.480C>G mutation was inherited from his mother, and the c.2929C>T mutation was inherited from his father. The RT-PCR and sequencing results showed that the c.480C>G mutation caused mRNA splicing in the proband and his mother, resulting in the deletion of 99 bases in c.476G-574A (p.S160-S192). qRT-PCR showed that the c.2929C>T variant reduced the mRNA level of the ITGA2B gene in the proband and his father. Bioinformatics analysis suggested that the c.480C>G mutation might form a binding sequence with hnRNP A1 protein and generate the 5'SS splice site. The three-dimensional structural model of the αⅡb subunit showed that the β-propeller domain of the p.S160-S192 deletion lost two β-strands and one α-helix in blade 2. The c.2929C>T nonsense mutation caused premature translation termination and produced a truncated protein with the deletion of p.R977-E1039, including the cytoplasmic domain, transmembrane domain, and a β chain of the extracellular Calf-2 domain. The total αⅡb expression of the proband was absent, and the relative expression of β3 was 11.36% of the normal level. Conclusion: The compound heterozygous mutation c.480C>G in exon 4 and c.2929C>T in exon 28 of the ITGA2B gene probably underlies Glanzmann thrombasthenia in this pedigree.

Double jeopardy, glomangiopericytoma and Glanzmann thrombasthenia resulting in recurrent epistaxis: a case report

Glanzmann thrombasthenia is a rare bleeding disorder induced by inherited defects of the platelet membrane αIIbβ3 glycoprotein. Glomangiopericytoma, on the other hand, is a very rare sinonasal tumor demonstrating a perivascular myoid phenotype. We herein report the first described case in the literature of Glanzmann thrombasthenia and glomangiopericytoma. The patient is a 40-year-old man diagnosed with type 1 Glanzmann thrombasthenia who presented with repetitive and profuse posterior epistaxis initially managed with platelet transfusions and recombinant activated factor VII (rFVIIa). Due to the unresolved epistaxis, nasal endoscopy was performed revealing a vascularized tumor. Subsequently, a sphenopalatine artery embolization followed by a surgical excision of the tumor was performed. The pathology report diagnosis of the tumor was glomangiopericytoma. This case sheds the lights on a very rare cause of epistaxis in a patient with Glanzmann thrombasthenia, with a challenging multidisciplinary management. A local cause of epistaxis should always be considered even in case of a diagnosed bleeding disorder, especially when the bleeding is recurrent.

A bispecific antibody approach for the potential prophylactic treatment of inherited bleeding disorders

Inherited bleeding disorders such as Glanzmann thrombasthenia (GT) lack prophylactic treatment options. As a result, serious bleeding episodes are treated acutely with blood product transfusions or frequent, repeated intravenous administration of recombinant activated coagulation factor VII (rFVIIa). Here we describe HMB-001, a bispecific antibody designed to bind and accumulate endogenous FVIIa and deliver it to sites of vascular injury by targeting it to the TREM (triggering receptor expressed on myeloid cells)-like transcript-1 (TLT-1) receptor that is selectively expressed on activated platelets. In healthy nonhuman primates, HMB-001 prolonged the half-life of endogenous FVIIa, resulting in its accumulation. Mouse bleeding studies confirmed antibody-mediated potentiation of FVIIa hemostatic activity by TLT-1 targeting. In ex vivo models of GT, HMB-001 localized FVIIa on activated platelets and potentiated fibrin-dependent platelet aggregation. Taken together, these results indicate that HMB-001 has the potential to offer subcutaneous prophylactic treatment to prevent bleeds in people with GT and other inherited bleeding disorders, with a low-frequency dosing regimen.

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.

Two case reports of Glanzmann thrombasthenia with intracranial hemorrhage and a review of the literature

Background

Glanzmann's thrombasthenia (GT) is a rare autosomal recessive disorder characterized by impaired platelet function. Symptoms range from mild to life-threatening bleeding. However, it is extremely rare for a patient to have intracranial bleeding. This study presents two cases of GT: one with a spontaneous epidural hematoma (EDH) and the other with a subarachnoid hemorrhage due to traumatic causes. The discussion that follows then derives relevant supporting insights through a review of the literature.

Case Description

Case Report 1: A 9-year-old girl with a known case of GT presented to an emergency department with a severe headache but no other complaints or history of trauma. The physical examination was normal. Computed tomography (CT) head without contrast revealed multiple EDHs with no midline shift. She received factor VII, tranexamic acid, and platelets transfusion and was admitted to the intensive care unit to be managed conservatively. After a month, a CT head follow-up showed complete resolution of all hematomas. Case Report 2: A 20-year-old male with a known case of GT was brought to the hospital with a history of loss of consciousness for several minutes after a road traffic accident. He suffered from a headache on regaining consciousness and received analgesia. CT head showed diffuse subarachnoid hemorrhage. He was managed with factor VII, tranexamic acid, and platelets transfusion and was admitted to an intermediate care unit for close observation.

Conclusion

In a GT patient with intracranial hemorrhage, conservative management with close clinical observation and platelet transfusion in combination with recombinant activated factor VII and/or antifibrinolytics can be safely conducted.

A comprehensive review of the ten main platelet receptors involved in platelet activity and cardiovascular disease

Cardiovascular disease (CVD) is a major cause of death worldwide. Although there are many variables that contribute to the development of this disease, it is predominantly the activity of platelets that provides the mechanisms by which this disease prevails. While there are numerous platelet receptors expressed on the surface of platelets, it is largely the consensus that there are 10 main platelet receptors that contribute to a majority of platelet function. Understanding these key platelet receptors is vitally important for patients suffering from myocardial infarction, CVD, and many other diseases that arise due to overactivation or mutations of these receptors. The goal of this manuscript is to review the main platelet receptors that contribute most to platelet activity.

Effect of c.1431C > T mutation, a causative mutation of Glanzmann's thrombasthenia, on ITGB3 splicing, gene and protein expression

BACKGROUND/AIM

Recently, it was reported that the non-synonymous c.1431C > T (p. G477=) mutation of the integrin subunit β3 (ITGB3) gene is the cause of Glanzmann's thrombasthenia (GT). However, the functional consequences of this mutation on the ITGB3 gene and protein expression remain to be elucidated. Therefore, this study was conducted to cover this scientific shortage.

METHODS

Peripheral blood samples were collected from Chinese family members (parents and proband and his sister), and DNA was extracted and sequenced using whole-exome and Sanger sequencing. The effect of c.1431C > T mutation on the splicing of mRNA was verified by the in vitro minigene assay and the three variants that resulted from the mutation were cloned into a phage vector and pEGFP-C1 vector, and ITGB3 gene and protein expression was detected in the transfected 293 T cells using qPCR and Western blotting.

RESULTS

Minigene splicing assay showed that c.1431C > T mutation causes three kinds of alternative splicing; (1) a 95 bp deletion in the middle of exon10, (2) a 155 bp deletion (95 bp deletion in the middle of exon10 plus a 60 bp deletion in the right side of exon10), and (3) a 261 bp deletion in the right side of exon10. The in vitro expression assay showed that the c.1431C > T variant did not affect the ITGB3 mRNA levels, but directly led to protein truncation and declined expression.

CONCLUSION

Due to its significant impact on protein expression, c.1431C > T mutation in ITGB3 could be considered a pathogenic variant of GT. This could enrich the ITGB3 mutation spectrum and provide a base for the genetic diagnosis of GT.

SINE-VNTR-Alu retrotransposon insertion as a novel mutational event underlying Glanzmann thrombasthenia

BACKGROUND

Glanzmann thrombasthenia (GT) is an autosomal recessive platelet aggregation disorder caused by mutations in ITGA2B or ITGB3.

OBJECTIVES

We aimed to assess the phenotype and investigate the genetic etiology of a GT pedigree.

METHODS

A patient with bleeding manifestations and mild mental retardation was enrolled. Complete blood count, coagulation, and platelet aggregation tests were performed. Causal mutations were identified via whole exome and genome sequencing and subsequently confirmed through polymerase chain reaction and Sanger sequencing. The transcription of ITGB3 was characterized using RNA sequencing and reverse transcription polymerase chain reaction. The αⅡb and β3 biosynthesis was investigated via whole blood flow cytometry and in vitro studies.

RESULTS

GT was diagnosed in a patient with defective platelet aggregation. Novel compound heterozygous ITGB3 variants were identified, with a maternal nonsense mutation (c.2222G>A, p.Trp741∗) and a paternal SINE-VNTR-Alu (SVA) retrotransposon insertion. The 5' truncated SVA element was inserted in a sense orientation in intron 11 of ITGB3, resulting in aberrant splicing of ITGB3 and significantly reducing β3 protein content. Meanwhile, both the expression and transportation of β3 were damaged by the ITGB3 c.2222G>A. Almost no αⅡb and β3 expressions were detected on the patient's platelets surface.

CONCLUSION

Novel compound heterozygous ITGB3 mutations were identified in the GT pedigree, resulting in defects of αⅡbβ3 biosynthesis. This is the first report of SVA retrotransposon insertion in the genetic pathogenesis of GT. Our study highlights the importance of combining multiple high-throughput sequencing technologies for the molecular diagnosis of genetic disorders.

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.

Glanzmann's thrombasthenia associated with gastrointestinal angiodysplasias successfully treated with bevacizumab

Glanzmann's Thrombasthenia (GT) is a rare hemorrhagic condition caused by a platelet surface receptor disorder of the glycoprotein (GP) IIb/IIIa. Symptoms of GT are various forms of hemorrhages, such as purpura, epistaxis and menorrhagia. Gastrointestinal bleeding (GIB) is a rare expression of the condition and may occur due to traumas in the GI tract or as a consequence of gastrointestinal angiodysplasia (GIADs). In this case report, we present a middle-aged woman with recurrent GIB consequent to GIADs with persistent melena and iron deficiency anemia. After several unsuccessful therapeutic interventions, the patient was studied by the hereditary hemorrhagic telangiectasia's (HHT - Osler-Weber-Rendu disease) unit, where she received bevacizumab, showing a complete improvement in symptoms as well as a reduction in her GIADs. This case shows that bevacizumab could be a possible line of treatment for patients with coagulation disorders with GIADs.

Glanzmann Thrombasthenia Associated with Siderotic Synovitis and Arthropathy: A Case Report

Glanzmann thrombasthenia is a bleeding disorder with a low incidence. It typically manifests as superficial bleeding episodes, which tend to be mild. Deep organ involvement is not uncommon but remains rare due to the rarity of the disease itself and the unusual association between platelet disorders and deep organ implications. A 17-year-old boy with Glanzmann thrombasthenia since infancy developed ankle pain after a minor trauma. His initial workup was negative, but he continued to experience ankle pain. A magnetic resonance imaging (MRI) done after four weeks suggested siderotic synovitis. The patient was lost to follow-up after that and returned after two years with recurrent left ankle pain. Imaging and studies have shown evidence of chronic arthropathy. A specialized orthopedic team assessed the patient. The patient underwent intra-articular steroid injection for pain relief and was referred to continue physical therapy. In conclusion, hemarthrosis is more common in hemophilia than in platelet disorders and has potential morbidity and quality-of-life implications.

LSD1 knockdown confers protection against osteoclast formation by reducing histone 3 lysine 9 monomethylation and dimethylation in ITGB3 promoter

ITGB3, an osteoclast marker, is involved in osteoclast formation. Nevertheless, its related mechanism remains poorly characterized. Herein, this study examines the mechanisms affecting osteoclast formation with the involvement of ITGB3. Osteoclast formation was induced with macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-kappa B ligand (RANKL), followed by measurement of the mRNA and protein expression of ITGB3 and LSD1. After gain- and loss-of-function assays, cell viability and the expression of osteoclast marker genes (NFATc1, ACP5, and CTSK) were assessed, and osteoclast formation was evaluated with TRAP staining. ChIP assays were used to examine histone 3 lysine 9 (H3K9) monomethylation (H3K9me1) and H3K9 dimethylation (H3K9me2) modifications and LSD1 protein enrichment in the ITGB3 promoter. During osteoclast formation, ITGB3 and LSD1 were gradually augmented. Knockdown of LSD1 or ITGB3 curbed cell viability, the expression of osteoclast marker genes, and osteoclast formation. Moreover, overexpression of ITGB3 nullified the suppressive impact of LSD1 knockdown on osteoclast formation. Mechanistically, LSD1 promoted ITGB3 expression by reducing H3K9 levels in the ITGB3 promoter. LSD1 enhanced ITGB3 expression by decreasing H3K9me1 and H3K9me2 levels in ITGB3 promoter to boost osteoclast formation.

Antagonistic Roles of Human Platelet Integrin αIIbβ3 and Chemokines in Regulating Neutrophil Activation and Fate on Arterial Thrombi Under Flow

BACKGROUND

Platelets and neutrophils are the first blood cells accumulating at sites of arterial thrombus formation, and both cell types contribute to the pathology of thrombotic events. We aimed to identify key interaction mechanisms between these cells using microfluidic approaches.

METHODS

Whole-blood perfusion was performed over a collagen surface at arterial shear rate. Platelet and leukocyte (in majority neutrophil) activation were microscopically visualized using fluorescent markers. The contributions of platelet-adhesive receptors (integrin, P-selectin, CD40L) and chemokines were studied by using inhibitors or antibodies and using blood from patients with GT (Glanzmann thrombasthenia) lacking platelet-expressed αIIbβ3.

RESULTS

We observed (1) an unknown role of activated platelet integrin αIIbß3 preventing leukocyte adhesion, which was overcome by short-term flow disturbance provoking massive adhesion; (2) that platelet-expressed CD40L controls the crawling pattern and thrombus fidelity of the cells on a thrombus; (3) that continued secretion of platelet substances promotes activation of identified neutrophils, as assessed by (fMLP [N-formylmethionyl-leucyl-phenylalanine, a potent chemotactic agent and leukocyte activator] induced) [Ca2+]i rises and antigen expression; (4) and that platelet-released chemokines activate the adhered cells in the order of CXCL7>CCL5>CXCL4. Furthermore, postsilencing of the platelets in a thrombus suppressed the leukocyte activation. However, the leukocytes on thrombi did no more than limitedly form neutrophil extracellular traps, unless stimulated with phorbol ester or lipopolysaccharide.

CONCLUSIONS

Together, these findings reveal a multifaceted regulation of adhesion and activation of neutrophils by platelets in a thrombus, with a balanced role of several platelet-adhesive receptors and a promoting role of platelet-released substances. This multivalent nature of neutrophil-thrombus interactions offers novel prospects for pharmacological intervention.

A single F153Sβ3 mutation causes constitutive integrin αIIbβ3 activation in a variant form of Glanzmann thrombasthenia

This report identifies a novel variant form of the inherited bleeding disorder Glanzmann thrombasthenia, exhibiting only mild bleeding in a physically active individual. The platelets cannot aggregate ex vivo with physiologic agonists of activation, although microfluidic analysis with whole blood displays moderate ex vivo platelet adhesion and aggregation consistent with mild bleeding. Immunocytometry shows reduced expression of αIIbβ3 on quiescent platelets that spontaneously bind/store fibrinogen, and activation-dependent antibodies (ligand-induced binding site-319.4 and PAC-1) report β3 extension suggesting an intrinsic activation phenotype. Genetic analysis reveals a single F153Sβ3 substitution within the βI-domain from a heterozygous T556C nucleotide substitution of ITGB3 exon 4 in conjunction with a previously reported IVS5(+1)G>A splice site mutation with undetectable platelet messenger RNA accounting for hemizygous expression of S153β3. F153 is completely conserved among β3 of several species and all human β-integrin subunits suggesting that it may play a vital role in integrin structure/function. Mutagenesis of αIIb-F153Sβ3 also displays reduced levels of a constitutively activated αIIb-S153β3 on HEK293T cells. The overall structural analysis suggests that a bulky aromatic, nonpolar amino acid (F,W)153β3 is critical for maintaining the resting conformation of α2- and α1-helices of the βI-domain because small amino acid substitutions (S,A) facilitate an unhindered inward movement of the α2- and α1-helices of the βI-domain toward the constitutively active αIIbβ3 conformation, while a bulky aromatic, polar amino acid (Y) hinders such movements and restrains αIIbβ3 activation. The data collectively demonstrate that disruption of F153β3 can significantly alter normal integrin/platelet function, although reduced expression of αIIb-S153β3 may be compensated by a hyperactive conformation that promotes viable hemostasis.

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.

Hemorrhage of Upper Digestive and Respiratory Tracts in a Child with Glanzmann Thrombasthenia

Glanzmann thrombasthenia (GT) is an autosomal recessive platelet disorder that could cause mild to severe bleeding episodes. The incidence is approximately 1 per 1,000,000 births. Patients with GT frequently have mucocutaneous bleeding with absent platelet aggregation in response to all physiologic stimuli, but a normal platelet count and morphology. Specifically, the glycoprotein IIb/IIIa (GP IIb/IIIa) complex is either inadequate or dysfunctional. This case reports a 3.5-year-old boy with Glanzmann thrombasthenia who had two episodes with uncontrolled hemorrhage from upper digestive and respiratory tracts, the first with the bleeding point found in the left tonsil and the second in the adenoids.

Apixaban for treatment of venous thromboembolism in an obese patient with Glanzmann thrombasthenia

Background

Glanzmann thrombasthenia (GT) is a rare congenital platelet function disorder associated with a severe bleeding diathesis. Thrombotic manifestations remain a rare condition. We report here the first case of recurrent venous thromboembolism (VTE) successfully treated with apixaban in a patient with GT. Our patient's morbid obesity was an additional challenge.

Key Clinical Question

The Key Clinical Question was to determine if direct oral anticoagulants are suitable for patients with both obesity and GT.

Clinical Approach

In our patient, the first episode of VTE occurred after the use of a low dose of activated recombinant factor VII for a minor procedure, whereas the second was unprovoked. Administration of rivaroxaban very quickly led to the appearance of bleeding symptoms and subsequently led to poor compliance and extension of deep vein thrombosis. The patient was switched to apixaban, with very good efficacy and safety over the cumulative 18 months of use.

Conclusion

The last updated guidelines now recommend the use of rivaroxaban and apixaban for management of VTE in patients with obesity. Regarding patients with GT, there is still insufficient data on the use of direct oral anticoagulants. Management of thrombotic manifestations in these patients remains a rare and complex condition and could be improved by the creation of a specific international registry.

Extracellular Vesicle ITGAM and ITGB2 Mediate Severe Acute Pancreatitis-Related Acute Lung Injury

Integrins expressed on extracellular vesicles (EVs) secreted by various cancers are reported to mediate the organotropism of these EVs. Our previous experiment found that pancreatic tissue of mice with severe cases of acute pancreatitis (SAP) overexpresses several integrins and that serum EVs of these mice (SAP-EVs) can mediate acute lung injury (ALI). It is unclear if SAP-EV express integrins that can promote their accumulation in the lung to promote ALI. Here, we report that SAP-EV overexpress several integrins and that preincubation of SAP-EV with the integrin antagonist peptide HYD-1 markedly attenuates their pulmonary inflammation and disrupt the pulmonary microvascular endothelial cell (PMVEC) barrier. Further, we report that injecting SAP mice with EVs engineered to overexpress two of these integrins (ITGAM and ITGB2) can attenuate the pulmonary accumulation of pancreas-derived EVs and similarly decrease pulmonary inflammation and disruption of the endothelial cell barrier. Based on these findings, we propose that pancreatic EVs can mediate ALI in SAP patients and that this injury response could be attenuated by administering EVs that overexpress ITGAM and/or ITGB2, which is worthy of further study due to the lack of effective therapies for SAP-induced ALI.

Monozygotic twin cases of endometriosis with Glanzmann thrombasthenia: a case report and review of literature

BACKGROUND

Glanzmann thrombasthenia (GT) is a rare bleeding disorder with a high prevalence in communities where consanguineous marriages are mainstream. Endometriosis is a chronic inflammatory disease, and its risk increases in women with menstrual periods of longer than six days. The phenotypic expression of endometriosis is determined by the frequency and rate of the menstrual flow, as well as genetic and environmental factors.

RESULT AND CASE PRESENTATION

14-year-old monozygotic twin sisters with GT who developed ovarian endometriosis were referred to Hazrat Rasoul Hospital due to severe dysmenorrhea. In ultrasonic examination, endometrioma cysts were reported in both patients. They both went under endometrioma cystectomy, and the bleeding was managed using antifibrinolytic drugs, followed by recombinant activated coagulation factor VII. Both were discharged after 3 days. In the ultrasound examination performed one year after the surgery, ovaries were normal in the first twin, while the second twin had a 28 × 30 hemorrhagic cyst in the left ovary.

DISCUSSION AND CONCLUSION

Menstrual bleeding and genetic factors are two theories that could be related to GT and endometriosis association, and GT could be considered a risk factor for endometriosis.

Unexplained bruising in an infant: Glanzmann thrombasthenia

Glanzmann thrombasthenia is a rare clotting disorder caused by impaired platelet function that can present with unexplained bruising. We present the case of a 4-month-old girl and outline the assessment and management of this condition, as well as an algorithm for the evaluation of abnormal bleeding and bruising.

Integrin αIIbβ3 intermediates: From molecular dynamics to adhesion assembly

The platelet integrin αIIbβ3 undergoes long-range conformational transitions associated with its functional conversion from inactive (low-affinity) to active (high-affinity) during hemostasis. Although new conformations that are intermediate between the well-characterized bent and extended states have been identified, their molecular dynamic properties and functions in the assembly of adhesions remain largely unexplored. In this study, we evaluated the properties of intermediate conformations of integrin αIIbβ3 and characterized their effects on the assembly of adhesions by combining all-atom simulations, principal component analysis, and mesoscale modeling. Our results show that in the low-affinity, bent conformation, the integrin ectodomain tends to pivot around the legs; in intermediate conformations, the headpiece becomes partially extended, away from the lower legs. In the fully open, active state, αIIbβ3 is flexible, and the motions between headpiece and lower legs are accompanied by fluctuations of the transmembrane helices. At the mesoscale, bent integrins form only unstable adhesions, but intermediate or open conformations stabilize the adhesions. These studies reveal a mechanism by which small variations in ligand binding affinity and enhancement of the ligand-bound lifetime in the presence of actin retrograde flow stabilize αIIbβ3 integrin adhesions.

Proteomic landscapes of inherited platelet disorders with different etiologies

BACKGROUND

Inherited platelet disorders (IPDs) are a heterogeneous group of rare diseases that are caused by the defects in early megakaryopoiesis, proplatelet formation, and/or mature platelet function. Although genomic sequencing is increasingly used to identify genetic variants underlying IPD, this technique does not disclose resulting molecular changes that impact platelet function. Proteins are the functional units that shape platelet function; however, insights into how variants that cause IPDs impact platelet proteomes are limited.

OBJECTIVES

The objective of this study was to profile the platelet proteomics signatures of IPDs.

METHODS

We performed unbiased label-free quantitative mass spectrometry (MS)-based proteome profiling on platelets of 34 patients with IPDs with variants in 13 ISTH TIER1 genes that affect different stages of platelet development.

RESULTS

In line with the phenotypical heterogeneity between IPDs, proteomes were diverse between IPDs. We observed extensive proteomic alterations in patients with a GFI1B variant and for genetic variants in genes encoding proteins that impact cytoskeletal processes (MYH9, TUBB1, and WAS). Using the diversity between IPDs, we clustered protein dynamics, revealing disrupted protein-protein complexes. This analysis furthermore grouped proteins with similar cellular function and location, classifying mitochondrial protein constituents and identifying both known and putative novel alpha granule associated proteins.

CONCLUSIONS

With this study, we demonstrate a MS-based proteomics perspective to IPDs. By integrating the effects of IPDs that impact different aspects of platelet function, we dissected the biological contexts of protein alterations to gain further insights into the biology of platelet (dys)function.

Validation of immunofluorescence analysis of blood smears in patients with inherited platelet disorders

BACKGROUND

Inherited platelet disorders (IPDs) are rare diseases characterized by reduced blood platelet counts and/or impaired platelet function. Recognizing IPDs is advisable but often challenging. The diagnostic tools include clinical evaluation, platelet function tests, and molecular analyses. Demonstration of a pathogenic genetic variant confirms IPDs. We established a method to assess the platelet phenotype on blood smears using immunofluorescence microscopy as a diagnostic tool for IPDs.

OBJECTIVES

The aim of the present study was to validate immunofluorescence microscopy as a screening tool for IPDs in comparison with genetic screening.

METHODS

We performed a blinded comparison between the diagnosis made using immunofluorescence microscopy on blood smears and genetic findings in a cohort of 43 families affected with 20 different genetically confirmed IPDs. In total, 76% of the cases had inherited thrombocytopenia.

RESULTS

Immunofluorescence correctly predicted the underlying IPD in the vast majority of patients with 1 of 9 IPDs for which the typical morphologic pattern is known. Thirty of the 43 enrolled families (70%) were affected by 1 of these 9 IPDs. For the other 11 forms of IPD, we describe alterations of platelet structure in 9 disorders and normal findings in 2 disorders.

CONCLUSION

Immunofluorescence microscopy on blood smears is an effective screening tool for 9 forms of IPD, which include the most frequent forms of inherited thrombocytopenia. Using this approach, typical changes in the phenotype may also be identified for other rare IPDs.