Hematopoietic Cells from Pluripotent Stem Cells: Hope and Promise for the Treatment of Inherited Blood Disorders

Inherited blood disorders comprise a large spectrum of diseases due to germline mutations in genes with key function in the hematopoietic system; they include immunodeficiencies, anemia or metabolic diseases. For most of them the only curative treatment is bone marrow transplantation, a procedure associated to severe complications; other therapies include red blood cell and platelet transfusions, which are dependent on donor availability. An alternative option is gene therapy, in which the wild-type form of the mutated gene is delivered into autologous hematopoietic stem cells using viral vectors. A more recent therapeutic perspective is gene correction through CRISPR/Cas9-mediated gene editing, that overcomes safety concerns due to insertional mutagenesis and allows correction of base substitutions in large size genes difficult to incorporate into vectors. However, applying this technique to genomic disorders caused by large gene deletions is challenging. Chromosomal transplantation has been proposed as a solution, using a universal source of wild-type chromosomes as donor, and induced pluripotent stem cells (iPSCs) as acceptor. One of the obstacles to be addressed for translating PSC research into clinical practice is the still unsatisfactory differentiation into transplantable hematopoietic stem or mature cells. We provide an overview of the recent progresses in this field and discuss challenges and potential of iPSC-based therapies for the treatment of inherited blood disorders.

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.

A coagulation defect arising from heterozygous premature termination of tissue factor

Tissue factor (TF) is the primary initiator of blood coagulation in vivo and the only blood coagulation factor for which a human genetic defect has not been described. As there are no routine clinical assays that capture the contribution of endogenous TF to coagulation initiation, the extent to which reduced TF activity contributes to unexplained bleeding is unknown. Using whole genome sequencing, we identified a heterozygous frameshift variant (p.Ser117HisfsTer10) in F3, the gene encoding TF, causing premature termination of TF (TFshort) in a woman with unexplained bleeding. Routine hematological laboratory evaluation of the proposita was normal. CRISPR-edited human induced pluripotent stem cells recapitulating the variant were differentiated into vascular smooth muscle and endothelial cells that demonstrated haploinsufficiency of TF. The variant F3 transcript is eliminated by nonsense-mediated decay. Neither overexpression nor addition of exogenous recombinant TFshort inhibited factor Xa or thrombin generation, excluding a dominant-negative mechanism. F3+/- mice provide an animal model of TF haploinsufficiency and exhibited prolonged bleeding times, impaired thrombus formation, and reduced survival following major injury. Heterozygous TF deficiency is present in at least 1 in 25,000 individuals and could limit coagulation initiation in undiagnosed individuals with abnormal bleeding but a normal routine laboratory evaluation.

Elevated thrombin generation in patients with congenital disorder of glycosylation and combined coagulation factor deficiencies

BACKGROUND

Congenital disorders of glycosylation are rare inherited diseases affecting many different proteins. The lack of glycosylation notably affects the hemostatic system and leads to deficiencies of both procoagulant and anticoagulant factors.

OBJECTIVE

To assess the hemostatic balance in patients with multiple coagulation disorders by using a thrombin generation assay.

METHOD

We performed conventional coagulation assays and a thrombin generation assay on samples from patients with congenital disorder of glycosylation. The thrombin generation assay was performed before and after activation of the protein C system by the addition of soluble thrombomodulin.

RESULTS

A total of 35 patients were included: 71% and 57% had low antithrombin and factor XI levels, respectively. Protein C and protein S levels were abnormally low in 29% and 26% of the patients, respectively, whereas only 11% displayed low factor IX levels. Under baseline conditions, the thrombin generation assay revealed a significantly higher endogenous thrombin potential and thrombin peak in patients, relative to controls. After spiking with thrombomodulin, we observed impaired involvement of the protein C system. Hence, 54% of patients displayed a hypercoagulant phenotype in vitro. All the patients with a history of stroke-like episodes or thrombosis displayed this hypercoagulant phenotype.

CONCLUSION

A thrombin generation assay revealed a hypercoagulant in vitro phenotype under baseline condition; this was accentuated by impaired involvement of the protein C system. This procoagulant phenotype may thus reflect the risk of severe vascular complications. Further research will have to determine whether the thrombin generation assay is predictive of vascular events.

Inherited Thrombophilia and the Risk of Arterial Ischemic Stroke: A Systematic Review and Meta-Analysis

Background Inherited thrombophilias are well-established predisposing factors for venous thromboembolism, but their role in arterial thrombosis, such as arterial ischemic stroke, remains uncertain. We aimed to evaluate the association between inherited thrombophilia (factor V Leiden, prothrombin G20210A mutation, protein C deficiency, protein S deficiency, and antithrombin deficiency) and risk of arterial ischemic stroke in adults. Methods and Results We searched PubMed, EMBASE, and Cochrane Library Databases from inception to December 31, 2018. We included case-control or cohort studies of adults reporting the prevalence of inherited thrombophilias in those with arterial ischemic stroke and subjects without arterial ischemic stroke. Two reviewers (T.C., E.D.) independently searched the literature and extracted data. Pooled odds ratios (ORs) and 95% CIs were calculated using random-effects model. We identified 68 eligible studies, which collectively enrolled 11 916 stroke patients and 96 057 controls. The number of studies reporting factor V Leiden, prothrombin G20210A mutation, protein C deficiency, protein S deficiency, and antithrombin deficiency were 56, 45, 15, 17, and 12, respectively. Compared with controls, patients with arterial ischemic stroke were significantly more likely to have the following inherited thrombophilias: factor V Leiden (OR, 1.25; 95% CI, 1.08-1.44; I2=0%), prothrombin G20210A mutation (OR, 1.48; 95% CI, 1.22-1.80; I2=0%), protein C deficiency (OR, 2.13; 95% CI, 1.16-3.90; I2=0%), and protein S deficiency (OR, 2.26; 95% CI, 1.34-3.80; I2=8.8%). Statistical significance was not reached for antithrombin deficiency (OR, 1.25; 95% CI, 0.58-2.67; I2=8.8%). Conclusions Inherited thrombophilias (factor V Leiden, prothrombin G20210A mutation, protein C deficiency, and protein S deficiency) are associated with an increased risk of arterial ischemic stroke in adults. The implications of these findings with respect to clinical management of patients with ischemic stroke require further investigation.

Exon 2 skipping eliminates γ-glutamyl carboxylase activity, indicating a partial splicing defect in a patient with vitamin K clotting factor deficiency

Essentials A carboxylase mutation that impairs splicing to delete exon 2 sequences was previously reported. We found that the mutant was inactive for vitamin K-dependent (VKD) protein carboxylation. An incomplete splicing defect likely accounts for VKD clotting activity observed in the patient. The results indicate the importance of proper carboxylase embedment in the membrane for function.

BACKGROUND

Mutations in the γ-glutamyl carboxylase (GGCX), which is required for vitamin K-dependent (VKD) protein activation, can result in vitamin K clotting factor deficiency (VKCFD1). A recent report described a VKCFD1 patient with a homozygous carboxylase mutation that altered splicing and deleted exon 2 (Δ2GGCX). Only Δ2GGCX RNA was observed in the patient.

OBJECTIVES

Loss of exon 2 results in the deletion of carboxylase sequences thought to be important for membrane topology and consequent function. Carboxylase activity is required for life, and we therefore tested whether the Δ2GGCX mutant is active.

METHODS

HEK 293 cells were edited by the use of CRISPR-Cas9 to eliminate endogenous carboxylase. Recombinant wild-type GGCX and recombinant Δ2GGCX were then expressed and tested for carboxylation of the VKD protein factor IX. A second approach was used to monitor carboxylation biochemically, using recombinant carboxylases expressed in insect cells that lack endogenous carboxylase.

RESULTS AND CONCLUSIONS

Δ2GGCX activity was undetectable in both assays, which is strikingly different from the low levels of carboxylase activity observed with other VKCFD1 mutants. The similarity in clotting function between patients with Δ2GGCX and these mutations must therefore arise from a novel mechanism. Low levels of properly spliced carboxylase RNA that produce full-length protein would not have been observed in the previous study. The results suggest that the splicing defect is incomplete. Δ2GGCX RNA has been detected in normal human liver, and has been designated carboxylase isoform 2; however, Δ2GGCX protein was not observed in normal human liver. The lack of activity and protein expression suggest that isoform 2 is not physiologically relevant to normal VKD protein carboxylation.

Diagnostic challenges of inherited mild bleeding disorders: a bait for poorly explored clinical and basic research

The best-known inherited mild bleeding disorders (MBDs), i.e. type 1 von Willebrand disease (VWD), platelet function disorders (PFDs), and mild to moderate clotting factor deficiencies, are characterized clinically by mucocutaneous bleeding, and, although they are highly prevalent, still pose difficult diagnostic problems. These include establishing the pathological nature of bleeding, and the uncertainties surrounding the clinical relevance of laboratory results. Furthermore, the high frequency of bleeding symptoms in the normal population and the subjective appraisal of symptoms by patients or parents makes elucidating the pathological nature of bleeding difficult. Standardized bleeding assessment tools and semiquantitative bleeding scores (BSs) help to discriminate normal from abnormal bleeding. However, as most MBDs have similar bleeding patterns, for example, bleeding sites, frequency, and severity, BSs are of little help for diagnosing specific diseases. Global tests of primary hemostasis (bleeding time; PFA-100/200) lack sensitivity and, like BSs, are not disease-specific. Problems with the diagnosis of type 1 VWD and PFD include assay standardization, uncertain definition of von Willebrand factor cut-off levels, and the lack of universal diagnostic criteria for PFD. Regarding clotting factor deficiencies, the bleeding thresholds of some coagulation factors, such as factor VII and FXI, are highly variable, and may lead to misinterpretation of the clinical relevance of mild to moderate deficiencies. Remarkably, a large proportion of MBDs remain undiagnosed even after comprehensive and repeated laboratory testing. These are tentatively considered to represent bleeding of undefined cause, with clinical features indistinguishable from those of classical MBD; the pathogenesis of this is probably multifactorial, and unveiling these mechanisms should constitute a fertile source of translational research.

Thrombophilic Genetic Anomalies and Their Association With Dialysis Initiation Age in a Cohort of Lebanese Hemodialysis Patients

OBJECTIVES

The relationship between chronic kidney disease and cardiovascular disease is complex and bidirectional. This relationship may be partially linked to thrombophilic genetic anomalies that may predispose to the progression of both diseases.

MATERIALS AND METHODS

We analyzed blood samples from 102 Lebanese patients with end-stage renal disease and undergoing hemodialysis and 20 randomly selected healthy volunteers for frequencies of 12 cardiovascular disease gene mutations and traditional risk factors. The frequencies of these mutations were calculated and compared in both groups. We stratified patients by quartiles according to their mean score of genetic mutations and traditional risk factors, as well as their mean age at dialysis initiation. Correlation analyses were performed on the various patient groups.

RESULTS

We observed a high frequency of mutations in patients on dialysis. Homozygous mutations (> 10% of patients) were observed in the PAI-1 (11%), MTHFR A1298C sequence variant (12.7%), and ACE genes (12%); in addition, the FXIII V34L and PAI-1 4G/5G genotypes were significantly associated with early dialysis initiation (P < .001 and P = .004, respectively). We observed a strong linear relationship between the different scores and age at dialysis initiation, with older patients exhibiting the highest genetic, traditional, and total scores versus those shown in the youngest patients (R2 = 0.72 and P < .001; R2 = 0.98 and P < .001; and R2 =0.96 and P < .001, respectively).

CONCLUSIONS

Our results revealed a polygenic thrombophilic profile in our population of Lebanese patients with end-stage renal disease. This profile showed a strong association between early dialysis initiation and specific homozygous cardiovascular disease gene mutations. The cumulative load of these genetic and traditional risk factors may be partly responsible for the increased risk of cardiovascular disease and risk of progression to end-stage renal disease in patients with chronic kidney disease.

The ISTH Bleeding Assessment Tool and the risk of future bleeding

Essentials ISTH Bleeding Assessment Tool (ISTH-BAT) is used to assist the diagnosis of bleeding disorders. We examined whether the ISTH-BAT is capable of predicting the risk of future bleeding. 136 subjects were administered the ISTH-BAT and followed for up to four years. The ISTH-BAT score failed to predict the risk of future bleeding.

SUMMARY

Background The ISTH Bleeding Assessment Tool (ISTH-BAT) is a diagnostic tool used in subjects with suspected inherited bleeding disorders. Aim To evaluate whether the ISTH-BAT, applied at first work-up in a tertiary-care center, predicts the risk of subsequent bleeding events. Methods This was an observational cohort study including all consecutive subjects, of either sex and any age, referred between 2011 and 2015 because of a suspected bleeding disorder. The analysis was restricted to those with an ISTH-BAT score of ≥ 3. Incidence rates (IRs) of major bleeding (MB) and clinically relevant non-major bleeding (CRNMB) events were calculated as the number of events over accrued person-years. The main analysis was performed with Cox regression analysis, assessing an ISTH-BAT score of ≤ 5 versus a score of > 5, as well as the score as a continuous variable, and various covariates (sex, age, and presence/absence of a final diagnosis). Results One hundred and thirty-six subjects had a median ISTH-BAT score of 4 (range 3-18). Eleven subjects (8.1%) had a bleeding event during follow-up (one MB event; 10 CRNMB events). The overall IR of bleeding events per 100 person-years was 3.7 (95% confidence interval [CI] 1.8-6.6). No difference was observed between subjects with an ISTH-BAT score of ≤ 5 and those with a score of > 5 (hazard ratio [HR] 1.2, 95% CI 0.3-4.6). The results were similar when the ISTH-BAT score was considered as a continuous variable (HR 1.1, 95% CI 0.9-1.4). The IR of bleeding was increased in individuals with a diagnosis of a hemostatic defect (IR of 7.5 per 100 person-years; HR 3.0, 95% CI 0.8-11.8). Conclusions The ISTH-BAT does not identify patients at increased risk of future bleeding events.

Hereditary Blood Coagulation Disorders: Management and Dental Treatment

Patients with hereditary hemostatic disorders, characterized by a tendency to bleeding or thrombosis, constitute a serious challenge in the dental practice. Advances in the medical diagnosis of hemostatic disorders have exposed dental professionals to new patients not amenable to the application of the management protocols associated with other, more well-known, disorders. It is the aim of this paper to review the evidence, to highlight the areas of major concern, and to suggest management regimens for patients with hereditary hemostatic disorders. An extensive review has been made (PubMed, Science Direct, Web of Knowledge, etc.) of literature pertaining to hereditary disorders affecting blood coagulation factors and how they affect the practice of dentistry. Several aspects relating to the care of such patients must be recognized and taken into consideration when dental treatment is planned. Replacement of deficient coagulation factors ensures that safe dental treatment will be carried out. However, the half-life of such coagulation factors requires that dental treatment be specifically planned and adapted to the type of pathology involved.

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.

Theories of Blood Coagulation

Although the concept of the coagulation cascade represented a significant advance in the understanding of coagulation and served for many years as a useful model, more recent clinical and experimental observations demonstrate that the cascade/waterfall hypothesis does not fully and completely reflect the events of hemostasis in vivo. The goal of this article is to review the evolution of the theories of coagulation and their proposed models to serve as a tool when reviewing the research and practice literature that was published in the context of these different theories over time.

New insights into the biology of tissue factor pathway inhibitor

Tissue factor pathway inhibitor (TFPI) dampens the initiation of blood coagulation by inhibiting two potent procoagulant complexes, tissue factor-factor VIIa (TF-FVIIa) and early forms of prothrombinase. TFPI isoforms, TFPIα and TFPIβ, result from alternative splicing of mRNA, producing distinct C-terminal ends of the two proteins. Both isoforms inhibit TF-FVIIa, but only TFPIα can inhibit early forms of prothrombinase by binding of its positively charged C-terminus with high affinity to the acidic B-domain exosite of FVa, which is generated upon activation by FXa. TFPIα and TFPIβ are produced in cultured human endothelial cells, while platelets contain only TFPIα. Knowledge of the anticoagulant mechanisms and tissue expression patterns of TFPIα and TFPIβ have improved our understanding of the phenotypes observed in different mouse models of TFPI deficiency, the east Texas bleeding disorder, and the development of pharmaceutical agents that block TFPI function to treat hemophilia.

Fibrinolysis and the control of blood coagulation

Fibrin plays an essential role in hemostasis as both the primary product of the coagulation cascade and the ultimate substrate for fibrinolysis. Fibrinolysis efficiency is greatly influenced by clot structure, fibrinogen isoforms and polymorphisms, the rate of thrombin generation, the reactivity of thrombus-associated cells such as platelets, and the overall biochemical environment. Regulation of the fibrinolytic system, like that of the coagulation cascade, is accomplished by a wide array of cofactors, receptors, and inhibitors. Fibrinolytic activity can be generated either on the surface of a fibrin-containing thrombus, or on cells that express profibrinolytic receptors. In a widening spectrum of clinical disorders, acquired and congenital defects in fibrinolysis contribute to disease morbidity, and new assays of global fibrinolysis now have potential predictive value in multiple clinical settings. Here, we summarize the basic elements of the fibrinolytic system, points of interaction with the coagulation pathway, and some recent clinical advances.

A self-controlled comparative clinical trial to explore the effectiveness of three topical hemostatic agents for stopping severe epistaxis in pediatrics with inherited coagulopathies

OBJECTIVE

The aim of this study was to assess the effectiveness of localized treatments to persistently stop epistaxis in patients with inherited bleeding disorders.

METHODS

In a self-controlled comparative clinical trial, to offer the best solution to stop epistaxis at home (within 10 minutes), patients with inherited bleeding disorders were treated using three different topical hemostatic agents, including Tranexamic acid impregnated tampon, EpiCell tampon prepared from oxidized regenerated cellulose pad, and ChitoHem tampon (reinforced with chitosan). The results of using these different products on three groups of randomly selected patients were ultimately compared using the χ(2) and Fisher's exact test statistics.

RESULTS

A total of 31 patients, 5 females and 26 males with a mean age of 5.6 years, were included in the study. Twenty-three patients had Glanzmann disease, four had von-Willebrand disease, two had Bernard soulier syndrome, two had activated factor VII deficiency, and one patient had impaired secretion of adenosine deaminase. The study exhibited that statistically there was no significant difference between EpiCell tampon and Tranexamic acid impregnated tampon treatments with respect to the hemostasis duration. However, ChitoHem tampon was more efficient than Tranexamic acid impregnated tampon (P value <0.001) and EpiCell tampon (P value < 0.05).

CONCLUSION

ChitoHem tampon, the chitosan-reinforced product, was the best therapy solution to stop epistaxis. We recommend further research on the use of other hemostatic agents for localized bleeding in patients with inherited bleeding disorders.

Thromboembolism in childhood nephrotic syndrome: A rare but serious complication

The main clinical features of nephrotic syndrome (NS) are heavy proteinuria, hypoalbuminemia, hyperlipidemia and edema. In addition, multiple abnormalities in the coagulation pathway may be a consequence of the NS. Both arterial and venous thromboembolic complications (TEC) are relatively common and serious consequences of NS. In addition, arterial and venous thrombosis might be unexpected events during an exacerbation of NS. Embolic episodes may manifest in different regions of the body such as the brain or the lung. Hence, predisposing factors, personal and family history of TEC, thrombosis location and evolution should be always investigated in children with NS.

Upper gastrointestinal bleeding in a young patient with Budd Chiari syndrome due to a mutation of factor V Leiden: a case report

Budd Chiari syndrome or hepatic venous outflow obstruction is a complex entity with multiple etiologies and various clinical manifestations. It is often difficult to establish the diagnosis. The most common cause is a hypercoagulable state due to either genetic disorders of blood coagulation or several acquired conditions such as hematological diseases, tumors, infections, chronic inflammatory diseases, pregnancy. The most common clinical presentation is hepatomegaly, abdominal pain and ascites, but the onset can also be dramatical and life threatening with upper digestive bleeding due to portal hypertension through postsinusoidal blockage. We report the case of a young patient with a coagulation disorder secondary to a mutation of factor V Leiden, who presented with upper digestive bleeding as the first manifestation of Budd Chiari syndrome and who also was associated with myocardial infarction in his past medical history.

The clinical significance of the lack of arterial or venous thrombosis in patients with congenital prothrombin or FX deficiency

Several reports have dealt with the occurrence of both arterial and venous thrombosis in patients with haemophilia A, haemophilia B, and von Willebrand disease. Similar thrombotic events have been occasionally reported also in rare congenital coagulation disorders, particularly in fibrinogen or FVII deficiencies. On the contrary no sure venous or arterial thrombotic event has ever been reported in congenital prothrombin or Factor X deficiency. The significance of this observation is discussed. This discrepancy cannot be explained on the basis of the rarity of the two conditions, since in similarly rare congenital bleeding disorders such as FV or FXIII deficiency a few patients with thrombosis have been described. It appears that only these two defects are able to allow a sure protection from thrombosis. These observations may indirectly support the rationale for the use of direct thrombin or Factor X inhibitors in the prophylaxis and/or therapy of thrombotic manifestations.

Thrombotic events in patients with congenital prekallikrein deficiency: a critical evaluation of all reported cases

The occurrence of thrombotic events in patients with congenital bleeding conditions has received considerable attention in recent years. The same is true for asymptomatic defects of factors of the contact phase of blood coagulation, mainly FXII. Anecdotal reports on thrombosis in patients with prekallikrein deficiency have occasionally been reported. These involved both arterial and venous thrombosis. The purpose of the present article is to analyze the stories and the clinical pictures of all 75 cases of prekallikrein deficiency published so far. Among these patients were 9 with thrombosis, 6 arterial (myocardial infarction and ischemic stroke) and 3 venous (deep vein thrombosis with or without pulmonary embolism). In 6 cases acquired thrombosis risk factors were present; in 2 cases no associated risk factors were present and in 1 case no information was supplied in this regard. One patient who presented both a stroke and a pulmonary embolism had a fatal outcome. The article clearly indicates that prekallikrein deficiency does not protect from thrombosis in spite of the severe in vitro coagulation defect.

[Congenital coagulopathies and coagulation factor inhibitors]

An overview is given on the clinical picture and therapy of the haemophilias A and B as an example for congenital coagulopathies. The survey deals with the special problems of today's "treated haemophilia" and its recommendations on diagnosis and treatment regimens. A special focus is put on the pathogenesis of the haemophilic joint arthropathy, that is affecting most haemophiliacs earlier or later during life. Safe plasma derived and recombinant clotting factor concentrates allow an efficient on-demand and also a prophylactic treatment for the prevention of bleeding sequelae. As a consequence life quality and life expectancy of today born haemophiliacs have nearly normalised. The problems of haemophilia with inhibitors and future therapeutic options are discussed. The development of inhibitors at start of therapy with factor VIII concentrates represent the nowadays most serious complication of haemophilia treatment. The only way to a long lasting eradication of the inhibitor ist the induction of immune tolerance that can be achieved by various protocols. A successful immune tolerance therapy (ITT) is the precondition for a regular prophylactic treatment regime. The Guidelines of the Federal Chamber of Physicians, the German recommendations for ITT and the consensus recommendations of an international working group provide an important lead for the conduction of immune tolerance therapy.

Coagulation disorders and inhibitors of coagulation in children from Mansoura, Egypt

Disorders of coagulation in children often prove challenging to the medical care team. The aims of this study were to assess the spectrum and prevalence of coagulation disorders among children attending Mansoura University Children Hospital (MUCH), Mansoura, Egypt. A total of 105 pediatric patients were referred to MUCH. They were divided into two groups: congenital coagulation disorders (75 cases, age 45.36 +/- 48.59 months), and acquired coagulation disorders (30 cases, age 56.13 +/- 61.61 months). All patients were subjected to thorough history taking including the nature of bleeding, family, past history, mode of inheritance, and detailed physical findings. Hemostatic tests included: platelet count, bleeding time (BT), prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT). Specific tests in the congenital group include assay of coagulation factors according to each disorder, Von Willebrand factor assay, ristocetin aggregation test, APTT mixing study for detection of inhibitors in complicated hemophilia cases, F VIII C to VWAg ratio with cut off 0.7 for detection of carriers in some hemophilia A families. Congenital disorders constituted 71.4% of the studied cases vs. 28.6% for acquired disorders. Hemophilia A (42.85%), hemophilia B (14.28%) and liver diseases (14.28%) represented the majority of the studied cases. Mild and moderate cases of hemophilia A and B are more frequent than severe cases in both types. Male sex is more frequent than female in the congenital group (94.7 vs. 5.3%, P < 0.001). Direct correlation existed between factor level assay and severity of hemophilia (r = 0.73, P = 0.006). Three mothers and one sister were identified as carrier out of four families. Anti-clotting factors inhibitor was detected in 18.2% of patients with hemophilia A and in 9.1% with hemophilia B. In conclusion, our study found that hemophilias are the most prevalent congenital coagulation disorders among children. Attention must be given for detection of hemophilia carriers and inhibitors of clotting factors.

Combined clotting factor deficiencies: experience at a single hemophilia treatment center

We describe a series of patients with combined factor deficiencies and von Willebrand's disease (VWD) at one haemophilia treatment centre. Although the incidence of VWD is at least 1% in the general population, combined coagulation defects have been infrequently described in the medical literature and are likely under diagnosed. This entity should be considered in patients with a known factor deficiency and either an unexpectedly severe bleeding phenotype, or bleeding that is unresponsive to factor replacement.

A novel fibrinogen variant (fibrinogen Seoul II; AαGln328Pro) characterized by impaired fibrin α-chain cross-linking

We report a novel fibrinogen variant (fibrinogen Seoul II), which has a heterozygous point mutation from CAA to CCA leading to AαGln328Pro. The mutation site is among several glutamine residues that serve as α-chain cross-linking acceptor sites. Fibrinogen Seoul II was found in a 51-year-old male patient and his family in Seoul, Korea. The patient was diagnosed with myocardial infarction at age 43. Eight years later he was admitted to the emergency room due to recurrence of the disease, where he expired under treatment with tissue plasminogen activator (t-PA). Fibrin polymerization curves, made using purified fibrinogen from the patient's relatives, showed a decreased final turbidity, suggesting Seoul II fibrin clots are composed of thinner fibers. This supposition was verified using scanning electron microscopy. Alpha-polymer formation by the mutant fibrinogen upon thrombin treatment in the presence of factor XIII and calcium was distinctly impaired. This result confirms that the residue Aα328 plays a pivotal role in α-chain cross-linking.

Inherited abnormalities of fibrinogen: 10-year clinical experience of an Italian group

Inherited abnormalities of fibrinogen present a high variability in penetrance and expressivity, and clinical manifestations vary from severe bleeding or thrombosis to asymptomatic This variability makes clinical and genetic counseling more difficult. We report the experience of a clinical group working in specialist centers in Southern Italy on a series of consecutive patients presenting with congenital abnormalities of fibrinogen. Over 10 years, 18 patients were diagnosed to carry a congenital abnormality of fibrinogen. These patients and 26 first-degree relatives were investigated in-depth to fully characterize the nature of their abnormal fibrinogen levels. A gene mutation was identified in 15 patients (four afibrinogenemic patients, three hypofibrinogenemic patients, and eight dysfibrinogenemic patients). A new mutation was found in four of them: Aalpha Arg159Stop in one afibrinogenemic patient, Aalpha Arg104Cys in two hypofibrinogenemic patients, and Aalpha Pro270Thr in one dysfibrinogenemic patient. While all afibrinogenemic patients had clinically important bleeding, participants presenting with hypofibrinogenemia remained asymptomatic. In the presence of the synthesis of an abnormal molecule, the clinical phenotype was not strictly related to plasma fibrinogen levels but was associated with the molecular defect, most carriers remaining asymptomatic. Personal and family histories of bleeding and thrombosis are important for the clinical management of patients presenting with congenital abnormalities of fibrinogen. Biochemical and genetic investigations may be a useful guide for decision-making, providing additional steps in the assessment of the risk of patients presenting with low levels of a normal molecule (hypofibrinogenemia and afibrinogenemia) and with an abnormal molecule (dysfibrinogenemia), respectively.

Molecular mechanisms of antithrombin deficiency in two Chinese families. One novel and one recurrent point mutation in the antithrombin gene causing venous thrombosis

We investigated the molecular mechanisms responsible for type I congenital antithrombin (AT) deficiency in two unrelated Chinese pedigrees manifesting multiple site venous thrombosis. Phenotype analysis showed both probands had almost 50% of normal AT levels. Direct sequencing of amplified DNA revealed 2757C > T in proband 1 and 13328G > A in proband 2, predicting a heterozygous Thr98Ile (T981) and Ala404Thr (A404T), respectively. No proband had 20210A allele or factor V Leiden mutation. Transient expression of complementary DNA coding for the mutations in COS-7 cells showed impaired secretion of the mutant molecules. Real-time quantitative PCR indicated that the mutant AT mRNA was transcribed at a similar or even higher level as that of wild-type (wt). Pulse-chase labeling studies suggested both AT variants did not accumulate, but degraded intracellularly. Immunohistochemical staining of the transfected cells revealed that CHO cells expressing the AT-198 mutant were stained diffusely without perinuclear enhancement and cells expressing AT-T404 mutant mainly in the whole cytoplasm with weaker perinuclear enhancement. We conclude that the impaired secretion of the mutant AT molecules, due to intracellular degradation, is the molecular pathogenesis of AT deficiency caused by T981 and A404T mutation for the two families, respectively.

The prevalence of viral hepatitis and HIV infections in patients with congenital bleeding disorders

Patients with clotting disorders, including hemophilias A and B, and von Willebrand Disease generally receive pooled human blood products, and are at high risk for HIV-1 and hepatitis A, B and C viral infection. This retrospective study describes patients receiving treatment at a federally funded Hemophilia Treatment Center (HTC) from 1998 - 2002 and assesses the prevalence of viral infection. In addition, current rates of viral infection are compared to 1984-1996 rates.

A novel missense mutation in ABCA1 results in altered protein trafficking and reduced phosphatidylserine translocation in a patient with Scott syndrome

Scott syndrome (SS) is a bleeding disorder characterized by a failure to expose phosphatidylserine (PS) to the outer leaflet of the platelet plasma membrane. Because the adenosine triphosphate (ATP)–binding cassette transporter A1 (ABCA1) is implicated in the exofacial translocation of PS, we assessed its role in the pathophysiology of a patient with SS. Substantially reduced levels of ABCA1 mRNA were found in the patient's leukocytes, compared with controls. The SS patient was heterozygous for a novel missense mutation c.6064G&gt;A (ABCA1 R1925Q), absent from unaffected family members and controls. Both mutant and wild-type alleles were reduced in mRNA expression, and no causative mutation for this phenomenon was identified in the ABCA1 gene or its proximal promoter, suggesting a putative second mutation in a trans-acting regulatory gene may also be involved in the disorder in this patient. In vitro expression studies showed impaired trafficking of ABCA1 R1925Q to the plasma membrane. Overexpression of wild-type ABCA1 in SS lymphocytes complemented the Ca2+-dependent PS exposure at the cell surface. These data identify a mutation in ABCA1 that contributes to the defective PS translocation phenotype in our patient with SS.

Inherited thrombophilia: an update

Inherited thrombophilia can be defined as a genetically determined predisposition to develop thromboembolic complications. Inherited prothrombotic risk factors include antithrombin deficiency, protein C and protein S deficiencies, activated protein C resistance due to factor V Leiden mutation, inherited hyperhomocysteinemia, prothrombin G20210A variant, dys- and hyperfibrinogenemia and elevated factor VIII levels. In this review we briefly analyze, from an epidemiologic, laboratory and clinical point of view, the main inherited prothrombotic risk factors. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in some conditions such as pregnancy and cardiovascular diseases.

The White platelet syndrome: a new autosomal dominant platelet disorder

The present study has evaluated 46 members from four generations of a large family with mild to moderate bleeding symptoms, prolonged bleeding times and poor responses to all aggregating agents. Twenty-one members of the family had all of the abnormal structural features of the disorder brought to Minnesota in 1870 by Esther White and, therefore, referred to as the White platelet syndrome (WPS). Their platelet counts were decreased and mean platelet volumes increased. Four to 13% of their platelets contained large, fully developed Golgi complexes actively budding smooth and coated vesicles and frequently associated with centrioles. Such structures are usually present in megakaryocytes only during the major phase of granulopoiesis. As many as seven Golgi complexes and five centrioles were present in single platelets. Alpha granule formation appeared incomplete in patient platelets. The organelles were often immature in appearance and markedly decreased in number in many of their cells. As a result 30% or more of WPS platelets were "gray platelets" similar to, yet very different from the cells in patients with the gray platelet syndrome. Other abnormal features included cytoplasmic sequestration by residual dense tubular system membranes, autodigestion, larger than normal mitochondria and half normal-sized dense bodies. Thirteen of the 46 family members had a "touch" of WPS. Three to 5% of their platelets contained Golgi complexes. However, gray platelets were not present among their circulating cells. The WPS is a unique autosomal dominant condition that can be classified among the platelet granule deficiency disorders.

[Menorrhagia and inherited disorders of coagulation]

Menorrhagia, a common complaint among women, may be a manifestation of an underlying inherited disorder of coagulation. In this review, the most frequent hereditary bleeding disorders associated with menorrhagia are briefly analyzed. Particularly, the epidemiological, clinical and diagnostic characteristics of von Willebrand disease, factor VIII, factor IX and factor XI deficiencies are examined. The influence of external factors (age, phase of menstrual cycle and hormonal therapy) on coagulation factor levels is also analyzed. Finally, the main therapeutic options (such as hormonal therapy, tranexamic acid and desmopressin), for the treatment of menorrhagia in women with hereditary bleeding disorders are reviewed. Since inherited bleeding disorders are frequently associated with menorrhagia, the conclusion is drawn that an underlying congenital bleeding disorder should be ruled out in any woman with menorrhagia.

[Studies on hereditary deficiency of coagulation factor V]

OBJECTIVE

To explore the mechanisms of hereditary deficiency of coagulation factor V (FV).

METHODS

The amount of FV in plasma and platelets was assayed by immunological and biochemical method, FV gene analysis by PCR product sequencing and restriction enzyme analysing, and the biostructural pathology of the identified mutation by molecular modeling.

RESULTS

No detectable FV fragments and FV activity were found in the plasma and platelets from the proband of the affected family. His gene analysis revealed a 1763A-->C substitution in a FV allele gene. The mutation might cause the loss of the hydrogen bond between conservative Tyr530 and Glu330, and form a cavity in the protein core.

CONCLUSION

The 1763A-->C mutation might cause the instability of FV and be the important mechanism for the hereditary deficiency of FV.