Osteonecrosis of the Femoral Head in Patients with Hypercoagulability-From Pathophysiology to Therapeutic Implications.

Osteonecrosis of the femoral head (ONFH) is a debilitating disease with major social and economic impacts. It frequently affects relatively young adults and has a predilection for rapid progression to femoral head collapse and end-stage hip arthritis. If not diagnosed and treated properly in the early stages, ONFH has devastating consequences and leads to mandatory total hip arthroplasty. The pathophysiology of non-traumatic ONFH is very complex and not fully understood. While multiple risk factors have been associated with secondary ONFH, there are still many cases in which a clear etiology cannot be established. Recognition of the prothrombotic state as part of the etiopathogeny of primary ONFH provides an opportunity for early medical intervention, with implications for both prophylaxis and therapy aimed at slowing or stopping the progression of the disease. Hereditary thrombophilia and hypofibrinolysis are associated with thrombotic occlusion of bone vessels. Anticoagulant treatment can change the natural course of the disease and improve patients' quality of life. The present work focused on highlighting the association between hereditary thrombophilia/hypofibrinolysis states and ONFH, emphasizing the importance of identifying this condition. We have also provided strong arguments to support the efficiency and safety of anticoagulant treatment in the early stages of the disease, encouraging etiological diagnosis and prompt therapeutic intervention. In the era of direct oral anticoagulants, new therapeutic options have become available, enabling better long-term compliance.

Genome-Wide Association Transethnic Meta-Analyses Identifies Novel Associations Regulating Coagulation Factor VIII and von Willebrand Factor Plasma Levels.

BACKGROUND: Factor VIII (FVIII) and its carrier protein von Willebrand factor (VWF) are associated with risk of arterial and venous thrombosis and with hemorrhagic disorders. We aimed to identify and functionally test novel genetic associations regulating plasma FVIII and VWF. METHODS: We meta-analyzed genome-wide association results from 46 354 individuals of European, African, East Asian, and Hispanic ancestry. All studies performed linear regression analysis using an additive genetic model and associated ≈35 million imputed variants with natural log-transformed phenotype levels. In vitro gene silencing in cultured endothelial cells was performed for candidate genes to provide additional evidence on association and function. Two-sample Mendelian randomization analyses were applied to test the causal role of FVIII and VWF plasma levels on the risk of arterial and venous thrombotic events. RESULTS: We identified 13 novel genome-wide significant ( P≤2.5×10-8) associations, 7 with FVIII levels ( FCHO2/TMEM171/TNPO1, HLA, SOX17/RP1, LINC00583/NFIB, RAB5C-KAT2A, RPL3/TAB1/SYNGR1, and ARSA) and 11 with VWF levels ( PDHB/PXK/KCTD6, SLC39A8, FCHO2/TMEM171/TNPO1, HLA, GIMAP7/GIMAP4, OR13C5/NIPSNAP, DAB2IP, C2CD4B, RAB5C-KAT2A, TAB1/SYNGR1, and ARSA), beyond 10 previously reported associations with these phenotypes. Functional validation provided further evidence of association for all loci on VWF except ARSA and DAB2IP. Mendelian randomization suggested causal effects of plasma FVIII activity levels on venous thrombosis and coronary artery disease risk and plasma VWF levels on ischemic stroke risk. CONCLUSIONS: The meta-analysis identified 13 novel genetic loci regulating FVIII and VWF plasma levels, 10 of which we validated functionally. We provide some evidence for a causal role of these proteins in thrombotic events.

Plasminogen replacement therapy for the treatment of children and adults with congenital plasminogen deficiency.

Congenital plasminogen deficiency is caused by mutations in PLG, the gene coding for production of the zymogen plasminogen, and is an ultrarare disorder associated with abnormal accumulation or growth of fibrin-rich pseudomembranous lesions on mucous membranes. Left untreated, these lesions may impair organ function and impact quality of life. Plasminogen replacement therapy should provide an effective treatment of the manifestations of congenital plasminogen deficiency. An open-label phase 2/3 study of human Glu-plasminogen administered IV at 6.6 mg/kg every 2 to 4 days in 15 patients with congenital plasminogen deficiency is ongoing. Reported here are data on 14 patients who completed at least 12 weeks of treatment. The primary end point was an increase in trough plasminogen activity levels by at least an absolute 10% above baseline. The secondary end point was clinical success, defined as ≥50% improvement in lesion number/size or functionality impact from baseline. All patients achieved at least an absolute 10% increase in trough plasminogen activity above baseline. Clinical success was observed in all patients with clinically visible (conjunctiva and gingiva), nonvisible (nasopharynx, bronchus, colon, kidney, cervix, and vagina), and wound-healing manifestations of the disease. Therapeutic effects were rapid, as all but 2 lesions resolved or improved after 4 weeks of treatment. Human Glu-plasminogen was well tolerated in both children and adults. This study provides critical first evidence of the clinical utility of ongoing replacement therapy with human Glu-plasminogen for the treatment of children and adults with congenital plasminogen deficiency. This trial was registered at www.clinicaltrials.gov as #NCT02690714.

Evaluation of Bleeding Phenotype of Inherited Factor VII Deficiency in Children With a Bleeding Assessment Tool and Global Assays.

INTRODUCTION: Inherited factor VII (FVII) deficiency is the most common of the rare bleeding disorders and shows a heterogenous distribution of bleeding phenotypes independent of factor activity level. The bleeding score (BS) evaluates the phenotype of patients with rare bleeding disorders. Thromboelastography (TEG) and thrombin generation assays (TGAs) are 2 methods to evaluate global hemostasis, and controversially both tests are useful for identifying different bleeding tendency phenotypes. The purpose of this study was to investigate the use of the BS and global assays (TEG and TGAs) to predict the bleeding phenotype of inherited FVII deficiency. MATERIALS AND METHODS: A total of 27 patients with FVII deficiency were evaluated with the BS and global hemostasis assays. RESULTS: The BS was compatible with disease severity according to the FVII activity level (P<0.05) but the BS and bleeding grade of patients did not show a statistically significant correlation with factor activity level (P>0.05). No significant correlation was observed between the factor activity level and any TEG parameter (P>0.05). The factor activity level was negatively correlated with the lag time of the TGA on the contrary positively correlated with the peak thrombin time of the TGA (P<0.05). CONCLUSIONS: The global assays do not successfully predict the bleeding phenotype. The BS is a more suitable tool than conventional and global assays for predicting the bleeding phenotype.

How I treat patients with inherited bleeding disorders who need anticoagulant therapy.

Situations that ordinarily necessitate consideration of anticoagulation, such as arterial and venous thrombotic events and prevention of stroke in atrial fibrillation, become challenging in patients with inherited bleeding disorders such as hemophilia A, hemophilia B, and von Willebrand disease. There are no evidence-based guidelines to direct therapy in these patients, and management strategies that incorporate anticoagulation must weigh a treatment that carries a risk of hemorrhage in a patient who is already at heightened risk against the potential consequences of not treating the thrombotic event. In this paper, we review atherothrombotic disease, venous thrombotic disease, and atrial fibrillation in patients with inherited bleeding disorders, and discuss strategies for using anticoagulants in this population using cases to illustrate these considerations.

A novel mutation in the F5 gene (factor V Amsterdam) associated with bleeding independent of factor V procoagulant function.

We investigated a small Dutch family with a bleeding diathesis, prolonged prothrombin, and activated partial thromboplastin times, in whom no classifying diagnosis was made. The 2 affected relatives had severely decreased in vitro thrombin generation, and levels of tissue factor pathway inhibitor (TFPI) were strongly increased. To identify the genetic cause of the bleeding diathesis, we performed whole exome sequencing analysis of all living relatives. We found a novel gain-of-function mutation in the F5 gene (c.C2588G), which leads to an aberrant splicing of F5 and ultimately to a short factor V protein (missing 623 amino acids from the B domain), which we called factor V Amsterdam. Factor V Amsterdam binds to TFPI, prolonging its half-life and concentration. This is the second report of an association between a shorter form of factor V and increased TFPI levels, resulting in severely reduced thrombin generation and a bleeding tendency.

Tissue Factor Pathway Inhibitor: Multiple Anticoagulant Activities for a Single Protein.

Tissue factor (TF) pathway inhibitor (TFPI) is an anticoagulant protein that inhibits early phases of the procoagulant response. Alternatively spliced isoforms of TFPI are differentially expressed by endothelial cells and human platelets and plasma. The TFPIß isoform localizes to the endothelium surface where it is a potent inhibitor of TF-factor VIIa complexes that initiate blood coagulation. The TFPIα isoform is present in platelets. TFPIα contains a stretch of 9 amino acids nearly identical to those found in the B-domain of factor V that are well conserved in mammals. These amino acids provide exosite binding to activated factor V, which allows for TFPIα to inhibit prothrombinase during the initiation phase of blood coagulation. Endogenous inhibition at this point in the coagulation cascade was only recently recognized and has provided a biochemical rationale to explain the pathophysiological mechanisms underlying several clinical disorders. These include the east Texas bleeding disorder that is caused by production of an altered form of factor V with high affinity for TFPI and a paradoxical procoagulant effect of heparins. In addition, these findings have led to ideas for pharmacological targeting of TFPI that may reduce bleeding in hemophilia patients.

An Unexpectedly High Rate of Thrombophilia Disorders in Patients with Superficial Vein Thrombosis of the Lower Extremities.

BACKGROUND: Superficial vein thrombosis (SVT) is a common venous condition. Recent studies have shown that SVT is associated with high frequency of thromboembolic complications: from 22-37% for deep venous thrombosis and up to 33% for pulmonary embolism. Our goal was to assess the prevalence of major hereditary and acquired thrombophilic factors in patients with SVT. METHODS: Sixty-six patients presenting with primary SVT underwent evaluation for thrombophilia: molecular testing for the factor V Leiden and factor II G20210 A (prothrombin) mutations, protein C, protein S, antithrombin deficiency, presence of lupus anticoagulant, as well as anticardiolipin antibody titers. Patients aged less than 18 years, with confirmed deep vein thrombosis, and pregnant women were excluded. RESULTS: 95.5% were Caucasian, and 62.1% were female gender. Age ranged from 21-88 years. Molecular testing showed that 34.2% of patients were heterozygous for factor V Leiden, 23.6% were heterozygous for the factor II mutation, 7.8% had antithrombin deficiency, 2.6% had protein S deficiency, and 2.1% had protein C deficiency. CONCLUSIONS: Our study showed that hereditary and acquired thrombophilias are higher than previously expected and reported.

Bleeding related to disturbed fibrinolysis.

The components and reactions of the fibrinolysis system are well understood. The pathway has fewer reactants and interactions than coagulation, but the generation of a complete quantitative model is complicated by the need to work at the solid-liquid interface of fibrin. Diagnostic tools to detect disease states due to malfunctions in the fibrinolysis pathway are also not so well developed as is the case with coagulation. However, there are clearly a number of inherited or acquired pathologies where hyperfibrinolysis is a serious, potentially life-threatening problem and a number of antifibrinolytc drugs are available to treat hyperfibrinolysis. These topics will be covered in the following review.

Diagnostics of Inherited Bleeding Disorders of Secondary Hemostasis: An Easy Guide for Routine Clinical Laboratories.

The investigation of inherited bleeding disorders of secondary hemostasis remains a challenge for most clinical laboratories, especially those that lack experience or specialized personnel. Bleeding can be essentially caused by a variety of acquired or congenital conditions, which impair either primary or secondary hemostasis. Since a universally agreed approach for the diagnostics of hemorrhagic disorders is still unavailable, this article aims to provide an easy guidance for routine clinical laboratories. This pragmatic approach to identifying and diagnosing inherited bleeding disorders of secondary hemostasis entails a multifaceted strategy, based on a collection of personal and family history, the results of first-line tests, which can then be followed by second- or third-line analyses to definitely establish the specific nature and the severity of the bleeding phenotype. Briefly, the presence of profound hemorrhages rather than mucocutaneous bleeding is suggestive of a disorder of secondary hemostasis. Although a positive family history is frequently reported in patients with congenital conditions, the lack of clinically meaningful symptoms in patient's relatives is not absolutely indicative of an acquired disorder. The next step encompasses the assessment of first-line coagulation tests (i.e., prothrombin time, activated partial thromboplastin time, and fibrinogen) if family history is not suggestive of a specific factor deficiency. The emergence of abnormal data of these assays and the variable combination of their results is then helpful to guide the performance of second-line tests, in particular specific factor assays, which will then provide a reasonable basis for a preliminary diagnosis. Third-line tests (namely, immunological assays of clotting factors and molecular biology) are then supportive for a final diagnosis and for identifying the nature of the factor deficiency (i.e., quantitative or functional).

A hereditary bleeding disorder resulting from a premature stop codon in thrombomodulin (p.Cys537Stop).

In this study, we describe a novel thrombomodulin (TM) mutation (c.1611C>A) that codes for a change from cysteine 537 to a premature stop codon (p.Cys537Stop). Three members of a family with a history of posttraumatic bleeding were identified to be heterozygous for this TM mutation. All coagulation screening tests, coagulation factor assays, and platelet function test results were within normal limits. However, the endogenous thrombin potential was markedly reduced at low-tissue factor concentration, and failure to correct with normal plasma indicated the presence of a coagulation inhibitor. Plasma TM levels were highly elevated (433-845 ng/ml, normal range 2-8 ng/ml, equating to 5 to 10 nM), and the addition of exogenous protein C further decreased thrombin generation. The mutation, p.Cys537Stop, results in a truncation within the carboxyl-terminal transmembrane helix. We predict that as a consequence of the truncation, the variant TM is shed from the endothelial surface into the blood plasma. This would promote systemic protein C activation and early cessation of thrombin generation within a developing hemostatic clot, thereby explaining the phenotype of posttraumatic bleeding observed within this family.

Beyond hemostasis: the challenge of treating plasminogen deficiency. A report of three cases.

Congenital plasminogen deficiency is a rare autosomal recessive disorder, characterized by chronic mucosal membranous lesions. Although the most common clinical manifestation is eye involvement as ligneous conjunctivitis, extra-ocular lesions affecting other mucosal surfaces indicates a systemic disease. In this report we describe two cases with atypical extra-ocular involvement that includes pericarditis and recurrent hematocolpos, and one with paradoxical correlation between ocular lesions and plasminogen levels. In ligneous conjunctivitis, although different treatment strategies have been tried with mild success, the only effective therapy is topical or systemic plasminogen concentrates that are not commercially available. Unfortunately there is not either effective management for cases with multisystemic disease. Hence, treatment for plasminogen deficiency is still a challenge and the variability of the clinical spectrum in this pathology makes necessary a multidisciplinary approach.

Newer Hemostatic Agents.

The mainstay of treatment of inherited coagulation disorders is based on the infusion of the deficient clotting factor, when available. Significant advances have been made over the past two decades in the production and availability of factor replacement products. In spite of such progression, several issue are still unsolved, the most important being the need for frequent factor concentrate infusions and the development of inhibitory alloantibodies. To overcome these important limitations, several newer hemostatic agents with an extended half-life are at an advanced stage of clinical development. After a brief overview of hemostasis, this narrative review summarizes the current knowledge on the most promising novel products for hemostasis. The current status of gene therapy for hemophilia, the only therapeutic option to definitively cure this inherited bleeding disorder, is also concisely discussed.

Disorders of coagulation in pregnancy.

The process of haemostasis is complex and is further complicated in the parturient because of the physiological changes of pregnancy. Understanding these changes and the impact that they have on the safety profile of the anaesthetic options for labour and delivery is crucial to any anaesthetist caring for the parturient. This article analyses current theories on coagulation and reviews the physiological changes to coagulation that occur during pregnancy and the best methods with which to evaluate coagulation. Finally, we examine some of the more common disorders of coagulation that occur during pregnancy, including von Willebrand disease, common factor deficiencies, platelet disorders, the parturient on anticoagulants, and the more rare acute fatty liver of pregnancy, with a focus on their implications for neuraxial anaesthesia.

Desmopressin (DDAVP) in the management of patients with congenital bleeding disorders.

Bleeding disorders, including haemophilia, von Willebrand disease, and platelet function abnormalities pose a substantial, ongoing management challenge. Patients with these disorders not only require treatment during bleeding events but also need effective management strategies to prepare for events ranging from minor dental procedures to major surgery and childbirth. Moreover, women with bleeding disorders often require ongoing treatment to prevent menorrhagia during childbearing years. Desmopressin (DDAVP), a synthetic derivative of the antidiuretic hormone l-arginine vasopressin, has become a well-established tool for the management of patients with bleeding disorders in a variety of clinical settings. However, despite the widespread use of DDAVP, the available clinical evidence on its efficacy and safety in these settings is limited, and there has not been a recent comprehensive review of its role in the clinical management of patients with bleeding disorders. As such, this article provides a review of the mechanism of action and pharmacokinetic properties of DDAVP, followed by a concise summary of the available evidence for its use in the treatment and prevention of bleeding.

Congenital prothrombin deficiency: an update.

Prothrombin (factor II [FII]) deficiency is a rare inherited coagulation disorder, having a prevalence of approximately 1 in 2,000,000. Two phenotypes can be distinguished: (1) true hypoprothrombinemia (type I deficiency), characterized by concomitantly low levels of the zymogen antigen; and (2) dysprothrombinemia (type II deficiency), characterized by the normal or near-normal synthesis of a dysfunctional protein. In the latter case, recent studies showed that particular mutations in the catalytic domain of active thrombin can even impair the enzyme interaction with antithrombin, favoring thromboembolic diseases. In some cases, hypoprothrombinemia associated with dysprothrombinemia was also described in compound heterozygous defects. Prothrombin is essential for the development of mammalian organisms. No living patient with undetectable plasma prothrombin has been reported to date. Prothrombin is encoded by a ≈21 kb gene located on chromosome 11 and containing 14 exons. Thirty-nine different mutations have been identified and characterized in prothrombin deficiency. Many of these are present in the catalytic site, whereas some involve regulatory domains, such as the anion-binding exosite I, the Na+-binding loop, and the light A-chain. Most hypoprothrombinemia-associated mutations are missense, but nonsense mutations leading to stop codons and one single nucleotide deletion have also been identified. Finally, recent developments in the therapy of congenital prothrombin deficiency are presented and discussed.

The outcome of endometrial ablation in women with inherited bleeding disorders.

There are currently limited data on the use of endometrial ablation in the treatment of heavy menstrual bleeding (HMB) in women with inherited bleeding disorders (IBDs). A retrospective review of prospectively collected data was performed. Twelve women with IBDs who had received endometrial ablation for the treatment of HMB were identified and their records reviewed. Details of their menstrual history; quality of life (QOL) and amount of menstrual blood loss [as assessed by pictorial blood-loss assessment chart (PBAC) and haemoglobin (Hb) concentration] pre and post-ablation were collected. Twelve women were included. The median duration of follow-up post-ablation was 32 months (range, 6-76). The median duration of menstruation decreased from 11 to 0 days after treatment (P = 0.004). Median PBAC scores decreased from 1208 preop to 0 post-ablation (P = 0.002).The median Hb concentrations (10.5-13.1 g dL(-1)) and QOL scores (median, 17-54) improved significantly after endometrial ablation (P < 0.01). Endometrial ablation appears to be a safe and effective long-term treatment for HMB in women with IDBs. It significantly decreases menstrual blood loss and improves QOL.