The use of recombinant factor VIIa in children with inherited platelet function disorders

Neurosurgical bleeding in platelet storage pool disorder: a case report

Dense-granule deficiency (DGD) is an inherited platelet disorder due to the absence of dense granules essential for activation of platelets in the event of vascular injury. Decreased platelet dense granules can be detected by electron microscopy, while other tests of hemostasis, including platelet function analyzer (PFA®) closure times, may be normal. The present case report describes a patient with a lifelong history of mucocutaneous bleeding and excessive hemorrhage with resection of vestibular Schwannoma. After hemostasis was obtained the case was aborted and the neurosurgeon noted bleeding resembled as if patient was on an antiplatelet drug. Subsequent hematologic workup revealed a severe platelet function disorder. There is a paucity of literature on management of intracranial neurosurgery in patients with inherited platelet disorders. Patients undergoing major surgical procedures often receive tranexamic acid (TXA), desmopressin, and/or human-leukocyte antigen (HLA)-matched platelet transfusions. We review the clinical management of intracranial tumor surgery, as well as Cyberknife radiosurgery, in our patient with DGD. After diagnosis was known, thoughtful hemostatic planning with empiric platelet transfusions and TXA prevented recurrent bleeding.

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.

Immune gene polymorphisms associated with poor response to platelet transfusion and recombinant factor VII administration in Glanzmann thrombasthenia

INTRODUCTION

Poor response to platelet and recombinant factor VII administration is a major problem in patients with Glanzmann Thrombasthenia (GT). The risk factors associated with poor response to treatment in these patients are unknown. Some genetic variations of cytokines may contribute to therapy resistance.

AIMS

We evaluated, for the first time, whether genetic polymorphisms on cytokine genes are related to poor treatment response in GT patients.

METHODS

We enrolled 30 patients with GT (15 resistant and 15 non-resistant) and 100 healthy controls. Gene polymorphisms of IL-10 and TNF-α were analysed using TaqMan Realtime PCR, and IL-1, IL-1R1 and IL-1RN were investigated with the RFLP method. In-silico analyses were performed to predict the potential impact of these polymorphisms.

RESULTS

In the resistant group, all patients had a variant of the IL-10 gene at the -1082 position (rs1800896), with a GG genotype that was significantly more frequent than the non-resistant group. Analysis between healthy controls and GT patients revealed a probable correlation between rs3783550, rs3783553, rs3917356 and rs2234463 and GT. The In-silico study indicated that TNF-α rs1800629 and IL-10 rs1800896 polymorphisms result in different allelic expressions which may contribute to poor response to therapy.

CONCLUSIONS

These findings suggest that polymorphisms in the IL-10 and IL-1 receptor antagonist genes may play a role in poor therapy response in GT patients. In addition, some polymorphisms in IL-1α, IL1-β, IL-1R1 and IL-R antagonists might be involved in the GT progression.

Rare bleeding disorders: Advances in management

Inherited factor coagulation deficiencies and vascular bleeding disorders, associated with bleeding of various severity, are often classified as rare bleeding disorders (RBDs). These include inherited fibrinogen disorders, inherited platelet function disorders (IPFD) and hereditary haemorrhagic telangiectasia (HHT). In the last decades, there have been large increases in knowledge on the epidemiology, genetics, physiopathology, clinical features, and diagnosis of RBDs, but improvements in management have been more limited and remain challenging. The treatment mainstay of RBDs is based only on replacement of a few available coagulation factor concentrates or cryoprecipitates. There is growing interest in therapeutic agents that enhance coagulation or inhibiting anticoagulant pathways in RBDs. In severe IPFD, the optimal platelet transfusion strategy is not yet established. Moreover, data is scarce on the effectiveness and safety of desmopressin and/or antifibrinolytic drugs often used for milder IPFD treatment. The best fibrinogen replacement strategy (prophylaxis vs. on demand) in afibrinogenemia is still debated. Similarly, the optimal trough fibrinogen target level for treatment of acute bleeding, and the role of fibrinogen replacement during pregnancy in mild hypofibrinogenemia and dysfibrinogenemia, have not been properly evaluated. The therapeutic arsenal in HHT includes antifibrinolytics and a series of antiangiogenic agents whose potential efficacy has been tested in small studies or are under investigation for treatment of bleeding. However, there is need to address several issues, including the optimal dosing strategies, the potential emergent toxicity of longer-term use, and the impact of systemic antiangiogenic treatment on visceral arteriovenous malformations.

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.

Treatment of Inherited Platelet Disorders: Current Status and Future Options

Inherited platelet disorders (IPDs) comprise a heterogeneous group of entities that manifest with variable bleeding tendencies. For successful treatment, the underlying platelet disorder, bleeding severity and location, age, and sex must be considered in the broader clinical context. Previous information from the AWMF S2K guideline #086-004 (www.awmf.org) is evaluated for validity and supplemented by information of new available and future treatment options and clinical scenarios that need specific measures. Special attention is given to the treatment of menorrhagia and risk management during pregnancy in women with IPDs. Established treatment options of IPDs include local hemostatic treatment, tranexamic acid, desmopressin, platelet concentrates, and recombinant activated factor VII. Hematopoietic stem cell therapy is a curative approach for selected patients. We also provide an outlook on promising new therapies. These include autologous hematopoietic stem cell gene therapy, artificial platelets and nanoparticles, and various other procoagulant treatments that are currently tested in clinical trials in the context of hemophilia.

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.

Difficulty in controlling heavy menstrual bleeding at menarche in a patient with Glanzmann's thrombasthenia

Glanzmann's thrombasthenia is a rare inherited autosomal recessive bleeding disorder caused by platelet dysfunction. Adolescent girls with Glanzmann's thrombasthenia may experience problematic heavy menstrual bleeding beginning at menarche; this can be difficult to manage. Here, we report the case of an 11-year-old girl with Glanzmann's thrombasthenia who presented with heavy menstrual bleeding at menarche, which was difficult to control. The vaginal bleeding persisted and did not respond to a treatment with packed red blood cells (16 U total), platelet concentrates (70 U total), or administration (>50 doses) of recombinant activated factor VII (rFVIIa). Eventually, a combination of rFVIIa and hormonal therapy (a combined oral contraceptive pill) was introduced. The bleeding stopped at nearly 1 month from onset of menarche. Thereafter, the condition was managed by monthly subcutaneous administration of a GnRH agonist. Management of severe menorrhagia in adolescent patients with Glanzmann's thrombasthenia requires close collaboration with gynecologists or adolescent medicine specialists. More clinical studies are required to identify an effective combination of rFVIIa and hormonal therapy for this condition.

The presentation and outcomes of Hermansky-Pudlak syndrome in obstetrics and gynecological settings: A systematic review

BACKGROUND

Hermansky-Pudlak syndrome (HPS) is a rare autosomal-recessive disorder with clinical manifestations of bleeding diathesis, multi-organ disease and variable oculocutaneous albinism (OCA). In women, it can cause life-threatening obstetric and gynecological (OB/GYN) bleeding.

OBJECTIVE

To summarize OB/GYN presentations, outcomes, and management strategies in women with HPS.

SEARCH STRATEGY

Main databases (MEDLINE, EMBASE, Cochrane, PubMed, Web of Science Core Collection and Google Scholar) were searched from inception until June 30, 2020.

SELECTION CRITERIA

Case reports/series of women with confirmed HPS.

DATA COLLECTION AND ANALYSIS

A systematic review using PRISMA guidelines. Methodological quality assessment performed using adapted Newcastle Ottawa scale.

MAIN RESULTS

A total 29 pregnancies in 15 women and 2 gynecological patients were identified. Heavy menstrual bleeding (HMB), the most common bleeding symptom, was reported in 8/15 (53%) of women. HMB and post-partum hemorrhage (PPH) led to diagnosis of HPS in 5/17 (29%) women. Primary PPH was reported in 12/27 (44%) of viable pregnancies; half were major PPH. In 17 pregnancies with known HPS diagnosis, 9 had hemostatic cover with desmopressin and 8 with platelet transfusion. Major PPH occurred in 3/9 (33%) pregnancies covered with desmopressin compared with none in the platelet group.

CONCLUSION

Diagnosis of HPS should be considered in women with OCA presenting with HMB or PPH. Hemostatic management options include desmopressin and platelet transfusion. Management should be multidisciplinary with close collaboration between OB/GYN and hematology teams.

Menstrual and obstetrical bleeding in women with inherited platelet receptor defects-A systematic review

INTRODUCTION

Women with inherited platelet receptor defects (IPRD) may have an increased risk of heavy menstrual bleeding (HMB) and postpartum haemorrhage (PPH).

AIM

To present a systematic overview of the literature on the prevalence and management of menstrual and obstetrical bleeding in women with IPRD.

METHODS

Electronic databases were searched for original patient data on the prevalence and management of HMB and PPH in women with known IPRD or who were being investigated for IPRD.

RESULTS

Sixty-nine papers (61 case reports/series and 8 cohort studies) were included. Overall, studies were rated as 'poor quality'. The included cohort studies reported HMB in 25% (13/52) of women with Bernard-Soulier syndrome and in 22.1% (34/154) of women with Glanzmann thrombasthenia. In total, 164 deliveries in women with IPRD were described. Excessive bleeding occurred in 16.9% (11/65) of deliveries described in the largest cohort. PPH occurred in 63.2% (55/87) of deliveries described in case reports/series. PPH occurred in 73.7% (14/19) of deliveries that were not covered by prophylaxis compared with 54.2% (32/59) of deliveries that were (OR = 2.36, 95% CI 0.75-7.40). Neonatal bleeding complications were reported in 10.0% (8/80) of deliveries. In all (6/6) deliveries with neonatal bleeding complications wherein the presence of alloantibodies was investigated, either antiplatelet or anti-HLA antibodies were detected.

DISCUSSION/CONCLUSION

Menstrual and particularly obstetrical bleeding problems frequently occur in women with IPRD, based on small case reports and series of poor quality. International collaboration, preferably on prospective studies, is needed to improve clinical management of women-specific bleeding in IPRD.

Inherited platelet functional disorders: General principles and practical aspects of management

Platelets are a critical component for effecting hemostasis and wound healing. Disorders affecting any platelet pathway mediating adhesion, activation, aggregation and procoagulant surface exposure can result in a bleeding diathesis. Specific diagnosis even with advanced techniques which are unavailable to most centers is often difficult. Inherited platelet function disorders therefore represent a heterogeneous and complex collection of disorders with a spectrum of bleeding severity, from relatively mild (and easily missed or misdiagnosed) to severe bleeding phenotype with salient diagnostic features. We advocate the use of bleeding assessment tools to help identification of patients and more importantly for assessment of individual patient bleeding phenotype to guide management decisions for treating and preventing bleeding. The complex management of these patients is best coordinated in a multidisciplinary comprehensive care clinic setting expert in managing bleeding disorders and associated complications, with particular attention to the physical and psychosocial health of patients and their families. Depending on the bleeding phenotype, the location and severity of bleeding, and the nature of an invasive procedure, available treatment modalities range from conservative measures using local pressure, topical thrombin, fibrin sealant, antifibrinolytics etc. to the use of systemic haemostatics such as desmopressin (DDAVP), platelets and recombinant human activated factor VII (rFVIIa). This review will provide opinions on the practical aspects and general management of inherited platelet function disorders, with discussion on the mechanism of action, and the pros and cons of various hemostatic agents. Finally, the prospect of curative treatment for patients with severe bleeding phenotype refractory to available treatments and with poor quality of life will be briefly discussed.

Acquired Antibodies to αIIbβ3 in Glanzmann Thrombasthenia: From Transfusion and Pregnancy to Bone Marrow Transplants and Beyond

Patients with the inherited bleeding disorder Glanzmann thrombasthenia (GT) possess platelets that lack αIIbβ3 integrin and fail to aggregate, and have moderate to severe mucocutaneous bleeding. Many become refractory to platelet transfusions due to the formation of isoantibodies to αIIbβ3 with the rapid elimination of donor platelets and/or a block of function. Epitope characterization has shown isoantibodies to be polyclonal and to recognize different epitopes on the integrin with β3 a major site and αvβ3 on endothelial and vascular cells a newly recognized target. Pregnancy in GT can also lead to isoantibody formation when fetal cells with β3 integrins pass into the circulation of a mother lacking them; a consequence is neonatal thrombocytopenia and a high risk of mortality. Antibody removal prior to donor transfusions can provide transient relief, but all evidence points to recombinant FVIIa as the first choice for GT patients either to stop bleeding or as prophylaxis. Promoting thrombin generation by rFVIIa favors GT platelet interaction with fibrin, and the risk of deep vein thrombosis also associated with prolonged immobilization and catheter use requires surveillance. Although having a high risk, allogeneic bone marrow transplantation associated with different stem cell sources and conditioning regimens has proved successful in many cases of severe GT with antibodies, and often, the associated conditioning and immunosuppressive therapy leads to loss of isoantibody production. Animal models of gene therapy for GT show promising results, but isoantibody production can be stimulated and CRISPR/Cas9 technology has yet to be applied. Up-to-date consensus protocols for dealing with isoantibodies in GT are urgently required, and networks providing patient care should be expanded.

Indication for allogeneic stem cell transplantation in Glanzmann’s thrombasthenia

Glanzmann’s thrombasthenia (GT) is an autosomal recessive disorder characterized by a lack of thrombocyte aggregation due to the absence of thrombocyte glycoproteins IIb and αIIbβ3. The role of haematopoietic stem cell transplantation (HSCT) in GT remains controversial. However, HSCT offers the only curative approach for patients with a severe clinical phenotype.

In this review, we will discuss the limitation of current status evidence and the specific risk of GT, in particular the alloimmunization and refractoriness to thrombocyte infusions. 19 successful HSCT in 18 GT type I patients have been reported. Mean age at transplantation was 5 years. All patients are still alive. The majority received sibling bone marrow transplant with busulfan and cyclophosphamid conditioning. GvHD incidence was within the normal range, but 10 patients showed alloimmunization of thrombocytes. Median follow up is 25 months.

Evaluation of Off-Label Recombinant Activated Factor VII for Multiple Indications in Children

Despite a paucity of safety and efficacy data, the use of recombinant activated factor VII in children for off-label indications has now surpassed its use in hemophilia. A retrospective chart review was conducted of 46 subjects (age, 6.7 ± 6 years; weight, 26 ± 20 kg) who received recombinant activated factor VII for nonhemophiliac indications between January 1, 2004, and September 1, 2005. Indications for use included prevention (n = 6) or treatment (n = 40) of bleeding due to general surgery, hepatic failure, gastrointestinal bleeding, severe traumatic brain injury, bone marrow transplant, cardiac, acetaminophen overdose, and multiorgan system failure. Decreases in prothrombin time, partial thromboplastin time, and international normalized ratio were observed. No inappropriate thrombotic events were noted. Administration of recombinant activated factor VII was associated with a reduction in coagulation markers without obvious adverse thrombotic events at cost of $4189 per dose. These findings should be confirmed in a prospective trial.

Control of Bleeding Caused by Thrombocytopenia Associated With Hematologic Malignancy: An Audit of the Clinical Use of Recombinant Activated Factor VII

This paper presents an analysis of 24 cases in which recombinant factor VIIa (rFVIIa) was used in the management of hemorrhage in patients with thrombocytopenia associated with hematologic malignancies. This is the largest case aggregation to date and focuses on preliminary experience in the off-label use of this hemostatic agent. Data were extracted from the international, Internet-based registry, www.haemostasis.com, accessed in September 2003. The search results were manually cross-checked against monthly summary reports. The physicians providing the cases were contacted individually to approve the use of their cases, supply any information missing from the database, and validate the data already held. Patients with acute myeloid leukemia, acute lymphoblastic leukemia, Hodgkin’s disease, non-Hodgkin’s lymphoma, Burkitt’s lymphoma, B-cell or T-cell lymphoma, or aplastic anemia received rFVIIa at total doses of between 18 and 1040 μg/kg body weight. Bleeding stopped in 11 of 24 (46%) patients, markedly decreased in 8 of 24 (33%) patients, and decreased in 4 of 24 (17%) patients. In most patients, the response was achieved within 2.5 hours of administration of rFVIIa. The use of rFVIIa was generally well tolerated—1 case of ischemic stroke was considered to be possibly related to rFVIIa administration, but this has yet to be confirmed. A review of these 24 cases submitted to the www.haemostasis.com database suggests that rFVIIa is beneficial in the management of hemorrhage in patients with thrombocytopenia and hematologic malignancies. This warrants further investigation in rigorously controlled clinical trials.

[Therapy of inherited diseases of platelet function. Interdisciplinary S2K guideline of the Permanent Paediatric Committee of the Society of Thrombosis and Haemostasis Research (GTH e. V.)]

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

NovoSeven (recombinant factor VIIa) for the treatment of bleeding episodes and perioperative management in patients with Glanzmann's thrombasthenia

Glanzmann's thrombasthenia is a rare inherited autosomal recessive bleeding disorder caused by qualitative or quantitative defects of the platelet membrane glycoprotein IIb/IIIa. The ensuing lack of platelet aggregation is frequently associated with mucocutaneous bleeding that may be variable in both frequency and intensity, ranging from minimal bruising to severe and life-threatening hemorrhages. A number of treatment modalities have been proposed to manage the bleeding episodes, which include local measures, antifibrinolytic agents, platelet transfusions and recombinant activated factor VII. The role of this bypassing hemostatic agent for treatment or prevention of bleeding episodes in Glanzmann's thrombasthenia patients is critically analyzed in this review.

The international, prospective Glanzmann Thrombasthenia Registry: treatment modalities and outcomes of non-surgical bleeding episodes in patients with Glanzmann thrombasthenia

Standard treatment for Glanzmann thrombasthenia is platelet transfusion. Recombinant activated factor VII has been shown to be successful in patients with Glanzmann thrombasthenia with platelet antibodies or who are refractory to platelet transfusions. The Glanzmann Thrombasthenia Registry prospectively collected worldwide information on the effectiveness and safety of platelet transfusion, recombinant activated factor VII and/or antifibrinolytics for the treatment of bleeds in patients with Glanzmann thrombasthenia. Data relating to 829 non-surgical bleeding episodes were entered into the Glanzmann Thrombasthenia Registry (severe/moderate: 216/613; spontaneous/post-traumatic: 630/199). Recombinant activated factor VII alone was used in 124/829 bleeds, recombinant activated factor VII+antifibrinolytics in 107/829, platelets±antifibrinolytics in 312/829, antifibrinolytics alone in 219/829, and recombinant activated factor VII+platelets±antifibrinolytics in 67/829. The proportion of successful treatments to stop bleeding was 91.0% in cases treated with recombinant activated factor VII only, 82.7% for recombinant activated factor VII+antifibrinolytics, 72.7% for treatment with recombinant activated factor VII+platelets±antifibrinolytics, 78.8% for platelets±antifibrinolytics and 84.7% for antifibrinolytics alone. Treatment failure was documented in 18 bleeding events (2% of the total treatments), the majority of which were in patients receiving treatment with antifibrinolytics; bleeding re-started in 6% of bleeds after initial effective treatment. Thirty-five adverse events were reported, none of which was a thromboembolic event. Among treatments that included recombinant activated factor VII, only one patient reported three possibly drug-related non-serious adverse events (nausea, dyspnea and headache). To conclude, non-surgical bleeds were common and often severe in Glanzmann thrombasthenia; both platelets and recombinant activated factor VII appeared to be effective, and with good safety profiles, for the treatment of non-surgical bleeds. This trial was registered at clinicaltrials.gov identifier: NCT01476423.

Non-myeloablative conditioning with busulfan before hematopoietic stem cell transplantation leads to phenotypic correction of murine Bernard-Soulier syndrome

BACKGROUND

Bernard-Soulier syndrome (BSS) is an inherited bleeding disorder characterized by macrothrombocytopenia. Platelet transfusion is used for the management of bleeding, but repeated transfusion often results in alloimmunization. We have recently shown phenotypic correction of murine BSS (GPIbα(null) ) using lethal radiation conditioning followed by hematopoietic lentivirus-mediated gene transfer.

OBJECTIVES

For application of gene therapy to treatment of human patients, it is important to minimize treatment-related side effects. The objective of this study is to model a clinically relevant non-myeloablative hematopoietic stem cell (HSC) transplantation strategy.

METHODS

Using transplantation of bone marrow (BM) HSCs from transgenic mice that express hGPIbα (hGPIbα(tg+/+) ), we sought to (i) determine the percentage of hGPIbα(tg+/+) HSCs required for therapeutic benefit, (ii) evaluate the efficacy of non-myeloablative conditioning using busulfan, and (iii) test the ability of anti-thymocyte globulin (ATG) to prevent/reduce undesirable immune responses.

RESULTS

Transplantation of 10-20% hGPIbα(tg+/+) BM HSCs mixed with GPIbα(null) BM HSCs into irradiated GPIbα(null) mice was sufficient to correct bleeding time (n = 5). Transplantation of hGPIbα(tg+/+) BM HSCs into busulfan-conditioned GPIbα(null) mice corrected bleeding time in 21 of 27 recipients. Antibody response to hGPIbα and immune-mediated thrombocytopenia was documented in eight of 27 recipients, suggesting immunogenicity of hGPIbα in busulfan-conditioned GPIbα(null) mice. However, these antibodies disappeared without treatment within 30 weeks after transplantation. A combination of busulfan plus ATG conditioning successfully prevented antibody development and significantly increased therapeutic engraftment.

CONCLUSION

A conditioning regimen of busulfan in combination with ATG could potentially be used in non-myeloablative autologous gene therapy in human BSS.

Recombinant Factor VIIa: clinical applications for an intravenous hemostatic agent with broad-spectrum potential

Recombinant Factor VIIa (NovoSeven, Novo Nordisk) is a unique hemostatic agent with potential for broad-spectrum applications in bleeding patients with congenital and acquired bleeding abnormalities. At present, recombinant Factor VIIa is only approved for the treatment of hemophilia A and B patients who have acquired antibodies to Factors VIII and IX. However, the literature is rapidly expanding indicating that rFVIIa could benefit patients with bleeding due to a variety of etiologies. Unfortunately, the vast majority of these reports are case studies or small-series summaries, and are neither prospective nor controlled. Controlled trials are currently underway in several potential areas of application. While the possibility of thrombotic complications has been a clinical concern, safety data on patients treated to date have not revealed a significant problem. Expansion of the clinical applications for this interesting and important hemostatic agent are hampered by its expense, the limited scope of the US Food and Drug Administration approval for its use, and the absence of an appropriate laboratory monitoring assay.

Inherited platelet function disorders: overview and disorders of granules, secretion, and signal transduction

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

Congenital thrombocytopenia: clinical manifestations, laboratory abnormalities, and molecular defects of a heterogeneous group of conditions

Once considered exceptionally rare, congenital thrombocytopenias are increasingly recognized as a heterogeneous group of disorders characterized by a reduction in platelet number and a bleeding tendency that may range from very mild to life threatening. Although some of these disorders affect only megakaryocytes and platelets, others involve different cell types and may result in characteristic phenotypic abnormalities. This review elaborates the clinical presentation and laboratory manifestations of common congenital thrombocytopenias in addition to exploring our understanding of the molecular basis of these disorders and therapeutic interventions available.

Experience with recombinant-activated factor VII in 30 patients with congenital factor VII deficiency

Recombinant-activated factor VII (rFVIIa) represents a therapeutic advance for the treatment and prevention of haemorrhage in patients with the rare bleeding disorder, congenital FVII deficiency. Thirty-nine cases of the use of rFVIIa in 30 patients with congenital FVII deficiency were identified from the international, internet-based registry haemostasis.com, which is a repository of case reports on the investigational use of rFVIIa that have been voluntarily submitted by physicians worldwide. These registry data have limitations compared with clinical-trial data but give valuable insights into a treatment for a rare disease that is virtually impossible to assess in conventional clinical trials. rFVIIa was used in: elective surgery (13 cases); haematoma (9 cases); emergency surgery (6 cases); epistaxis (4 cases); menorrhagia (2 cases); cover during childbirth (2 cases); disseminated intravascular coagulation (1 case; premature infant); removal of intradermal stitches (1 case); and haematuria (1 case). In 22/39 cases, rFVIIa was used prophylactically. Total dose and dosing schedules varied; median individual dose was 13.3 mug/kg body weight (bw) (range 1.2-223.8 mug/kg bw), median total dose was 38 microg/kg bw (range 1.2-758 microg/kg bw) and median number of doses was 3 (range 1-55). rFVIIa was generally associated with bleeding cessation or markedly reduced bleeding. Two adverse events were reported, but neither was regarded as being related to rFVIIa. These 39 cases support data confirming the safety and efficacy of rFVIIa in its EU-licensed indications, including that for preventing and/or controlling haemorrhage in patients with congenital FVII deficiency.

Treatment of inherited platelet disorders

For patients affected by severe inherited platelet dysfunctions, e.g. Glanzmann thrombasthenia (GT) or Bernard-Soulier syndrome (BSS), platelet transfusion is frequently needed for controlling spontaneous bleeding, and is always needed when trauma occurs or surgery is performed. For the mild-to-moderate bleeding entities, e.g. storage pool disease, thrombaxane A2 receptor defect, platelet transfusion is usually unnecessary. Transfusion of platelets should be used selectively and sparingly because of the substantial risk of alloimmunization against HLA antigens and/or platelet glycoproteins (GP) αIIb, β(3), or αIIbβ(3) in GT, and GPI-IX-V in BSS, which may lead to refractoriness to therapy. To reduce the risk, HLA-matched single donors of platelets should be used. If such donors are unavailable, leucocyte-depleted blood components should be used. Therapy other than platelet transfusion includes: (i) Prevention (vaccination against hepatitis B, avoidance of non-steroidal anti-inflammatory drugs, preservation of dental hygiene, correction of iron deficiency and prenatal diagnosis). (ii) Topical measures (compression with gauze soaked with tranexamic acid, fibrin sealants, splints for dental extractions and packing for nose bleeds). (iii) Antifibrinolytic agents that are useful for minor surgery and as adjuncts for other treatment modalities. (iv) Desmopressin that increases plasma levels of von Willebrand factor and factor VIII giving rise to increased platelet adhesiveness and aggregation associated with shortened bleeding time. (v) Recombinant factor VIIa (rFVIIa). GT patients have been treated for bleeding episodes by rFVIIa with partial success. The mechanism by which rFVIIa arrests bleeding is probably related to increased thrombin generation by a tissue factor-independent process, enhanced platelet adhesion and restoration of platelet aggregation. (vi) Female hormones. Excessive bleeding during menarche in patients with GT or BSS can be controlled by high doses of oestrogen followed by high doses of oral oestrogen-progestin. Menorrhagia later in life can be managed by continuous oral contraceptives. Depo-medroxyprogesterone acetate administered every 3 months is an alternative when combined oral contraceptives are contraindicated.

Molecular determinants of platelet delta storage pool deficiencies: an update

Delta storage pool deficiency (δ-SPD) is a rare heterogeneous group of platelet disorders characterized by a reduction in the number or content of dense granules. δ-SPD causes a mild to moderate bleeding diathesis characterized mainly by mucocutaneous bleeding. Currently, no specific treatment is available and the therapeutic approach is based on prevention of excessive bleeding. However, during the last few years, important insights into the pathophysiology of δ-SPD have been achieved using mouse models and dense granule deficiency-associated congenital diseases, such as Hermansky-Pudlak syndrome and Chediak-Higashi syndrome. It thus appears that δ-SPD represents a genetically heterogeneous group of intracellular vesicle biogenesis and/or trafficking disorders. This review summarizes recent data regarding the molecular mechanisms together with clinical features of the different types of δ-SPD. Although the molecular basis of isolated inherited δ-SPD remains currently unknown, next-generation sequencing strategies should enable researchers to identify the causative genes. Identification of those genes should contribute to our understanding of the pathophysiology, represent useful tools for genetic diagnosis, and eventually lead to new specific therapeutic approaches.

What To Do When You Suspect an Inherited Platelet Disorder

Inherited platelet disorders (IPDs) comprise a heterogenous group of diseases that include defects in platelet function and disordered megakaryopoiesis. Some IPDs overlap as both defects in function and thrombopoiesis, resulting in both altered aggregation and/or secretion and thrombocytopenia. This review examines the key features of the presentation of IPDs in children and adults and presents a diagnostic algorithm for the evaluation of these patients. In addition, recent advances in our understanding of the pathophysiology of platelet disorders are addressed, with attention given to some of the novel genetic associations. Finally, treatment options and future therapies are briefly discussed.

Treatment and outcomes for epistaxis in children with Glanzmann's thrombasthenia

OBJECTIVES/HYPOTHESIS

:To understand Glanzmann's thrombasthenia and provide insight to the management of epistaxis in children with this disease.

STUDY DESIGN

Retrospective chart review.

METHODS

All children diagnosed with Glanzmann's thrombasthenia and treated for epistaxis at Children's Hospitals and Clinics of Minnesota were identified and a retrospective chart review was performed. Outpatient charts, hospitalization records, and operative reports were reviewed from 1999 up to 2009 and appropriate data were extracted. The episodes of epistaxis, therapy used, complications, and success rates for controlling hemorrhage were noted.

RESULTS

Five children with a total of 63 clinical encounters for epistaxis were identified. Forty-seven encounters required hospitalization, close to half of which necessitated medical care in the intensive care unit. Nearly all encounters required infusion of hemostatic therapy with either single or multiple agents. Seventy-one procedures for life-threatening hemorrhage were performed. The most common (n = 24) intervention was administration of bovine collagen matrix, which was successful only half of the time (50%). Anterior and posterior nasal packing with or without hemostatic material completely resolved hemorrhage in 35% of the procedures.

CONCLUSIONS

To date, no form of medical or surgical intervention in children with this condition has consistently demonstrated its ability resolve nasal hemorrhage. The role of the otolaryngologist is to control bleeding during major episodes of nasal hemorrhage that do not respond to medical management. These patients usually have remarkable improvement in the frequency and severity of epistaxis in adolescence and then require much less aggressive therapy.

Diagnosis and Management of Inherited Platelet Disorders

In clinical daily practice the definition of a bleeding tendency is rather subjective. Clinical manifestations usually include hematoma, epistaxis, menorrhagia, and severe bleeding episodes after surgery or injuries. The most common causes are disorders of primary hemostasis that occur sometimes due to platelet function disorders. Inherited thrombocytopathies are much less frequent in comparison to acquired platelet function disorders. However, congenital disorders can lead to severe bleeding tendency and are often not diagnosed. They are induced by different platelet defects based on disorders of platelet adhesion, receptors, secretion, and signal transduction. In some cases, they are associated with thrombocytopenias, giant platelets, and various comorbidities. This article gives an overview of the different defects, their diagnosis, and treatment options.

Recombinant-activated factor VII for control and prevention of hemorrhage in nonhemophilic pediatric patients

A total of 108 episodes among 103 nonhemophilic pediatric patients (nine newborns, 16 infants and 78 children) treated with recombinant factor-activated VII (rFVIIa) were evaluated retrospectively. These episodes were divided into two groups: group 1 included 86 occurrences for hemorrhagic control of ongoing massive bleeding due to thrombocytopenia and coagulopathy unresponsive to blood component therapy in patients with dengue hemorrhagic fever, life-threatening, intraoperative and postoperative bleeding; group 2 included 22 episodes for prevention of hemorrhage with invasive procedures in patients with chronic liver disease and associated coagulopathy, and patients without preexisting hemostatic disorder but at high risk due to their underlying diagnosis and required surgical intervention. The effective control of hemostasis response rate in group 1 was significantly lower than in group 2. The median total dose per kilogram of rFVIIa group 1 was twice that of group 2. The overall case-fatality rate related to bleeding or underlying conditions was 31.1% (32/103). Adverse events were observed in three patients (2.9%) receiving rFVIIa for control of intraoperative and postoperative bleeding in the setting of corrective cardiac surgery. These results support the safety and potential benefit of rFVIIa for control and prevention of hemorrhage in pediatric patients without congenital hemophilia.

Intensive menstrual bleeding successfully treated with recombinant factor VIIa in Glanzmann thrombasthenia

Glanzmann thrombasthenia (GT) is a rare inherited qualitative platelet disorder due to the deficiency or defect of platelet membrane glycoprotein (GP) IIb/IIIa complex. Symptoms include purpura, petechiae, bruising, gingival bleeding, epistaxis, and menorrhagia. Platelet transfusion is considered the standard therapy for securing hemostasis in patients with GT when local measures and antifibrinolytic agents are inadequate. However, repeated platelet transfusions may result in GP IIb/IIIa and/or human leukocyte antigen (HLA) immunization and development of platelet refractoriness. Recombinant factor VIIa (rFVIIa) has been introduced as therapeutic alternative and has been suggested to be effective. Recombinant factor VIIa is indicated in Europe for the treatment of GT refractory of platelet transfusion. In previous studies, rFVIIa has been used in the prophylactic treatment of bleeding in patients with GT undergoing pelvic surgery, cesarean section, and vaginal delivery. In this article, we present a case of intensive menstrual bleeding refractory to previous antifibrinolytic agents and platelet transfusions but which responded well to treatment with rFVIIa. To our knowledge, there is no study or reported case in the literature reporting successful use of rFVIIa in a patient with excessive menstrual bleeding due to GT.

The use of recombinant FVIIa in a patient with Glanzmann thrombasthenia with uncontrolled bleeding after tonsillectomy

Glanzmann's thrombasthenia is an inherited platelet function disorder caused by quantitative or qualitative defects of the platelet membrane glycoprotein IIb/IIIa complex. Activated recombinant factor VII (rFVIIa) has recently been used in the treatment of patients with Glanzmann's thrombasthenia. We report herein a 16-year-old boy with Glanzmann's thrombasthenia who did not respond to conservative treatment for excessive bleeding and hyperfibrinolysis after tonsillectomy and who was successfully treated with rFVIIa. We suggest that rFVIIa at repeated doses of 80-100 microg/kg may be used effectively in patients with Glanzmann's thrombasthenia having excessive bleeding associated with hyperfibrinolysis after tonsillectomy in addition to tranexamic acid treatment.

Glanzmann thrombasthenia: an update

Glanzmann thrombasthenia (GT) is a rare autosomal recessive disorder characterized by qualitative or quantitative abnormalities of the platelet membrane glycoprotein (GP) IIb/IIIa. Physiologically, this platelet receptor normally binds several adhesive plasma proteins, and this facilitates attachment and aggregation of platelets to ensure thrombus formation at sites of vascular injury. The lack of resultant platelet aggregation in GT leads to mucocutaneous bleeding whose manifestation may be clinically variable, ranging from easy bruising to severe and potentially life-threatening hemorrhages. In this review we discuss the main characteristics of GT, focusing on molecular defects, diagnostic evaluation and treatment strategies.