Seminars in thrombosis and hemostasis最新文献

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.

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.

Background:  The activated partial thromboplastin time (aPTT) and anti-factor-Xa levels (anti-Xa) are both used to monitor patients on unfractionated heparin. Our previous study demonstrated that patients with discordant high aPTT relative to anti-Xa had higher rates of mortality and bleeding events.

Objective:  To determine if underlying patient characteristics drive both discordance and adverse outcomes or if discordance is an independent risk factor to adverse outcomes.

Methods:  We analyzed all patients hospitalized at the Stanford Hospital between January 2011 and December 2019 who had simultaneous aPTT and anti-Xa levels performed. From the electronic medical record, we extracted and analyzed 51 patient features including baseline coagulation laboratory results, demographics, values of other common laboratories (basic metabolic panel, complete blood count, etc.), diagnostic procedures, medications, and death.

Results:  A total of 17,728 patients had 78,701 paired aPTT and anti-Xa levels. Patients with discordant aPTT and anti-Xa where aPTT (seconds) was elevated beyond the expected therapeutic range had a higher 30-day mortality (odds ratio [OR]: 2.16, 95% confidence interval [CI]: 1.78-2.63, p < 0.001). Sectioning the patients based on the degree of discordance and whether aPTT or anti-Xa were signaling excess anticoagulation, we found those with an elevated aPTT discordant to their anti-Xa level had the highest odds of death (OR: 2.46, 95% CI: 1.99-3.10) compared with the concordant group. This finding was still present after controlling for patient comorbidity and other laboratory results at hospital admission.

Conclusion:  After controlling for patient features strongly associated with increased mortality in heparinized patients, we identified that the discordant pattern of high aPTT to anti-Xa served as an independent predictor of 30-day all-cause mortality, with a higher degree of discordance associated with increased odds of 30-day mortality.

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.

Vascular calcification (VC) commonly accompanies the development of atherosclerosis, defined by the accumulation of calcium in the arterial wall, potentially leading to stroke and myocardial infarction. Severe and unevenly distributed calcification poses challenges for interventional procedures, elevating the risks of vascular dissection, acute vascular occlusion, restenosis, and other major adverse cardiovascular events. Platelets promote the development of atherosclerosis by secreting various inflammatory mediators, regulating cell migration, aggregation, adhesion, and initiating and expanding inflammatory responses. There is emerging evidence that platelets play a direct role in VC; however, this novel concept has not yet been critically assessed. This review describes the intricate mechanisms by which platelets promote VC, focusing on three key aspects and the potential opportunities for their therapeutic targeting: extracellular vesicles, platelet-regulatory proteins, and indices related to platelet function.

Catastrophic thrombosis is a severe condition characterized by a hypercoagulable tendency, leading to multiple thromboembolic events in different blood vessels, usually within a short timeframe. Several conditions have been associated with the development of catastrophic thrombosis, including the catastrophic antiphospholipid syndrome, thrombotic anti-platelet factor 4 immune disorders, thrombotic microangiopathies, cancers, the hyper-eosinophilic syndrome, pregnancy, infections, trauma, and drugs. Thrombotic storm represents a medical emergency whose management represents a serious challenge for physicians. Besides the prompt start of anticoagulation, a patient's prognosis depends on early recognition and possible treatment of the underlying condition. In this narrative review, we summarize the main characteristics of catastrophic thrombosis, analyzing the various conditions triggering such life-threatening complication. Finally, an algorithm with the diagnostic workup and the initial management of patients with catastrophic thrombosis is presented.

External quality assessment (EQA) is used to evaluate laboratory performance in tests of hemostasis; however, some esoteric tests are performed by too few centers in any one EQA program to allow valid statistical assessment. To explore the feasibility of pooling data from several EQA providers, an exercise was carried out by the External Quality Assurance in Thrombosis and Haemostasis group, using the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee (SSC) plasma standard for thrombophilia screening assays. Six EQA providers took part in this exercise, distributing the SSC plasma standard as a "blinded" sample to participants for thrombophilia tests between November 2020 and December 2021. Data were collected by each provider, anonymized, and pooled for analysis. Results were analyzed as overall results from each EQA provider, and by kit/method-specific comparisons of data from all providers pooled together. For each parameter, median results and range were determined. Over 1,250 sets of data were returned in the six EQA programs. The overall medians (all data pooled) were <4% of the assigned values for each parameter with the exception of protein C activity by clot-based assay. Method-related differences in median results were observed for free protein S antigen and protein S activity-a pattern seen across data from the different EQA providers. Antithrombin antigen results reported in mg/dL provided an example where small numbers of results for a single EQA provider may be supplemented by pooling data from multiple providers with good agreement seen among results reported by the different EQA providers. This study demonstrated that a multicenter EQA provider collaboration can be carried out and demonstrated benefit for assays with smaller number of participants. In addition, results showed good agreement with the assigned values of the SSC plasma standard. Further exercises for tests performed by only small numbers of laboratories can be planned.

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.