Seminars in thrombosis and hemostasis最新文献

Congenital combined deficiency of factor V (FV) and factor VIII (FVIII; F5F8D, OMIM 227300) is a rare hereditary coagulopathy and accounts for approximately 3% of cases of rare coagulation disorders. The prevalence of this disease in the general population is estimated to be 1:1,000,000 and is significantly higher in regions where consanguineous marriages are permitted, such as the Mideast and South Asia. The disease has an autosomal recessive mode of inheritance and therefore occurs with an equal incidence among males and females. Heterozygous mutation carriers usually do not have clinical manifestations. The molecular basis of this disease differs from that of stand-alone congenital deficiencies of FVIII and FV. F5F8D is caused by mutations in either LMAN1 or MCFD2, which encode components of a cargo receptor complex for endoplasmic reticulum to Golgi transport of FV and FVIII, leading to defects in an intracellular transport pathway shared by these two coagulation factors. Congenital combined deficiency of FV and FVIII is characterized by decreased activities of both FV and FVIII in plasma, usually to 5 to 30% of normal. Clinical manifestations in most cases are represented by mild or moderate hemorrhagic syndrome. The simultaneous decreases of two coagulation factors present complications in the diagnosis and management of the disease. In female patients, the disease requires a special approach for family planning, pregnancy management, and parturition. This review summarizes recent progress in clinical, laboratory, and molecular understanding of this disorder.

Bernard-Soulier syndrome (BSS) is an inherited platelet function disorder caused by mutations in the genes that encode the glycoprotein (GP) Ibα and GPIbβ subunits, as well as the GPIX subunit in the GPIbIX complex, which is located on the platelet surface and has roles in platelet adhesion and activation. Patients with autosomal recessively inherited biallelic BSS have a homozygous or compound heterozygous expression in the GPIbα, GPIbβ, and GPIX subunits of the GPIbIX complex. Patients with autosomal dominantly inherited monoallelic BSS have a heterozygous expression in only the GPIbα and GPIbβ subunits of the GPIbIX complex. To date, no BSS mutations in the GP5 gene have been reported. Patients with biallelic form are usually diagnosed at a young age, typically with mucocutaneous bleeding, whereas monoallelic forms are generally identified later in life and are frequently misdiagnosed with immune thrombocytopenic purpura (ITP). In biallelic BSS, giant platelets in the peripheral blood smear, absence of ristocetin-induced platelet aggregation (RIPA) using light transmission aggregometry (LTA), and complete loss of GPIbIX complex in flow cytometry are observed, whereas in monoallelic forms, genetic diagnosis is recommended due to the presence of large platelets in the peripheral blood smear, decreased or normal RIPA response in LTA, and partial loss or normal GPIbIX complex in flow cytometry. Platelet transfusion is the main therapy but recombinant factor VIIa is advised in alloimmunized patients, and allogeneic stem cell transplantation is suggested in refractory cases. Antifibrinolytics and oral contraceptives are utilized as supplementary treatments. Finally, differentiation from ITP is critical due to differences in management. Thus, BSS should be kept in mind in the presence of individuals with chronic persistent thrombocytopenia, positive family history, unresponsive ITP treatment, macrothrombocytopenia, and absence of RIPA response.

Coagulation factor X (FX), originally named Stuart-Prower factor, plays a pivotal role in the coagulation cascade, activating thrombin to promote platelet plug formation and prevent excess blood loss. Genetic variants in F10 may lead to FX deficiency and to impaired coagulation. FX variants are phenotypically classified as being type I, with the concomitant reduction of FX coagulant activity and FX antigen levels or type II, corresponding to a reduction in activity with normal antigen plasma levels. Patients affected with FX deficiency tend to be one of the most seriously affected among those with rare bleeding disorders. They show a variable bleeding tendency strongly associated with FX coagulant activity levels in plasma and may present, in the severe form of the deficiency, life-threatening symptoms such as gastrointestinal and umbilical stump bleeding and intracranial hemorrhages or central nervous system bleeding. Treatment of FX deficiency was originally based on the replacement of the missing factor using fresh frozen plasma, cryoprecipitate and prothrombin complex concentrates; however, a plasma-derived concentrate, shown to be safe and effective in clinical trials, is now available. In addition, novel nonreplacement therapy such as small interference RNA, gene therapy, drug repurposing, and gene editing may also represent novel therapeutic approaches for FX deficiency, but further, much focused studies are needed before considering this emerging therapy in such patients.

Congenital factor VII (FVII) deficiency, the most frequent among the recessively inherited disorders of blood coagulation, is characterized by a wide range of symptoms, from mild mucosal bleeds to life-threatening intracranial hemorrhage. Complete FVII deficiency may cause perinatal lethality. Clinically relevant thresholds of plasma levels are still uncertain, and modest differences in low FVII levels are associated with large differences in clinical phenotypes. Activated FVII (FVIIa) expresses its physiological protease activity only in a complex with tissue factor (TF), which triggers clotting at a very low concentration. Knowledge of the FVIIa-TF complex helps to interpret the clinical findings associated with low FVII activity as compared with other rare bleeding disorders and permits effective management, including prophylaxis, with recombinant FVIIa, which, however, displays a short half-life. Newly devised substitutive and nonsubstitutive treatments, characterized by extended half-life properties, may further improve the quality of life of patients. Genetic diagnosis has been performed in thousands of patients with FVII deficiency, and among the heterogeneous F7 mutations, mostly missense changes, several recurrent variants show geographical distribution and identity by descent. In the general population, common F7 polymorphisms explain a large proportion of FVII level variance in plasma through FVII-lowering effects. Their combination with pathogenic variants may impact on the frequent detection of FVII coagulant levels lower than normal, as well as on mild bleeding conditions. In the twenties of this century, 70 years after the first report of FVII deficiency, more than 200 studies/reports about FVII/FVII deficiency have been published, with thousands of FVII-deficient patients characterized all over the world.

Factor V (FV) is a glycoprotein that plays a pivotal role in hemostasis, being involved in coagulant and anticoagulant pathways. Congenital FV deficiency is a rare bleeding disorder with an incidence of 1 per million live births, considering the most severe homozygous form. FV deficiency is diagnosed using routine coagulation tests and FV activity assays. Several mutations, including missense, nonsense, and frameshift, have been detected in the F5 gene. Clinical symptoms are variable, ranging from mild ecchymoses and mucosal bleeding to life-threatening intracranial hemorrhage. The mainstay of treatment includes fresh-frozen plasma, preferentially virus-inactivated. In this narrative review, we provide an update of the main laboratory, molecular, clinical, and therapeutic features of inherited FV deficiency.

Deficiencies in coagulation factors I (FI), FII, FV, combined FV and FVIII (CF5F8) and vitamin K-dependent coagulation factors FVII, FX, FXI, and FXIII have been referred to as rare bleeding disorders (RBDs), rare coagulation factor deficiencies (RCFDs), or recessively inherited coagulation disorders. Fibrinogen was most likely the first member of this group to be identified, with reports of its discovery spanning from 1859 to 1966. If not, then the first coagulation factor to be identified was prothrombin in 1894, and the last coagulation factor to be found was FX in 1956, about 60 years later. The first patient to be diagnosed with an RBD was a 9-year-old boy with afibrinogenemia in 1920 and the vitamin K-dependent coagulation factors deficiency was the most recent RBD in this group to be identified in a 3-month-old child in 1966. The initial therapeutic option for nearly all patients with RBDs was whole blood transfusion; this was replaced in 1941 by fresh frozen plasma (FFP), and then in later years by cryoprecipitate and coagulation factor concentrates. Fibrinogen concentrate was the first coagulation factor concentrate produced in 1956. Coagulation factor concentrate is now available for FI, FVII, FX, FXI, and FXIII; however, FFP and/or platelet transfusion are the only treatments available for FV deficiency. The only recombinant concentrates available for RBDs are for FVII and FXIII, which date from 1988 and the 2000s, respectively. Even though the clinical presentations, diagnosis, and management of lesser-known bleeding disorders have improved significantly in recent decades, more studies are needed to reveal the hidden aspects of these disorders in order to overcome diagnostic and therapeutic challenges and ultimately improve the quality of life for those who are affected.

von Willebrand disease (VWD) is the most common well-studied genetic bleeding disorder worldwide. Much less is known about platelet-type VWD (PT-VWD), a rare platelet function defect, and a "nonidentical" twin bleeding phenotype to type 2B VWD (2B-VWD). Rather than a defect in the von Willebrand factor (VWF) gene, PT-VWD is caused by a platelet GP1BA mutation leading to a hyperaffinity of the glycoprotein Ibα (GPIbα) platelet surface receptor for VWF, and thus increased platelet clearing and high-molecular-weight VWF multimer elimination. Nine GP1BA gene mutations are known. It is historically believed that this enhanced binding was enabled by the β-switch region of GPIbα adopting an extended β-hairpin form. Recent evidence suggests the pathological conformation that destabilizes the compact triangular form of the R-loop-the GPIbα protein's region for VWF binding. PT-VWD is often misdiagnosed as 2B-VWD, even the though distinction between the two is crucial for proper treatment, as the former requires platelet transfusions, while the latter requires VWF/FVIII concentrate administration. Nevertheless, these PT-VWD treatments remain unsatisfactory, owing to their high cost, low availability, risk of alloimmunity, and the need to carefully balance platelet administration. Antibodies such as 6B4 remain undependable as an alternative therapy due to their questionable efficacy and high costs for this purpose. On the other hand, synthetic peptide therapeutics developed with In-Silico Protein Synthesizer to disrupt the association between GPIbα and VWF show preliminary promise as a therapy based on in vitro experiments. Such peptides could serve as an effective diagnostic technology for discriminating between 2B-VWD and PT-VWD, or potentially all forms of VWD, based on their high specificity. This field is rapidly growing and the current review sheds light on the complex pathology and some novel potential therapeutic and diagnostic strategies.

Congenital fibrinogen disorders (CFDs) include afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia, and hypodysfibrinogenemia. The fibrinogen levels, the clinical features, and the genotype define several sub-types, each with specific biological and clinical issues. The diagnosis of CFDs is based on the measurement of activity and antigen fibrinogen levels as well as on the genotype. While relatively easy in quantitative fibrinogen disorders, the diagnosis can be more challenging in qualitative fibrinogen disorders depending on the reagents and methods used, and the underlying fibrinogen variants. Overall, quantitative and qualitative fibrinogen defects lead to a decrease in clottability, and usually in a bleeding tendency. The severity of the bleeding phenotype is moreover related to the concentration of fibrinogen. Paradoxically, patients with CFDs are also at risk of thrombotic events. The impact of the causative mutation on the structure and the fibrinogen level is one of the determinants of the thrombotic profile. Given the major role of fibrinogen in pregnancy, women with CFDs are particularly at risk of obstetrical adverse outcomes. The study of the fibrin clot properties can help to define the impact of fibrinogen disorders on the fibrin network. The development of next generation sequencing now allows the identification of genetic modifiers able to influence the global hemostasis balance in CFDs. Their integration in the assessment of the patient risk on an individual scale is an important step toward precision medicine in patients with such a heterogeneous clinical course.