Factor V Research Articles

Challenges in the diagnosis and management of patients with rare coagulation disorders in Lebanon and consequences of a social and economic crisis.

Rare coagulation disorders (RCDs) constitute an important health risk. Data on epidemiology, quality of life (QoL), access to care, and impact of the ongoing economic crisis on RCDs in Lebanon is limited. We aimed to address these gaps by evaluating effect of the crisis on themanagement of RCDs. We performed a retrospective chart review of RCD pediatric patients in a tertiary hospital between 2003 and 2023. Patients with deficiencies of fibrinogen, factor (F)II, FV, combined FV and FVIII, FVII, FXI, FXII, FXIII, and congenital deficiency of vitamin K-dependent factors (VKCFDs) underwent a qualitative assessment of the impact of the economic crisis on care and quality of life by an interview aimed at investigating obstacles to diagnosis, disparities in access to treatment, impact of the crisis on QoL and disease management, and opinion on governmental efforts to solve the health crisis. 46 patients were included. The response rate for the interview was 63%. Among the cohort, 21 (72.4%) reported difficulty accessing treatment since the start of the crisis and 18 (62%) reported "lack of healthcare coverage for necessary treatments" as the main issue. Most participants reported that the Lebanese government did not adequately address their needs during the crisis. Our study showcased that management of RCD patients in Lebanon has been severely affected by the economic crisis. Combined efforts by public and private sectors are needed to appropriately address this issue. Lessons can be learned from the Lebanese experience to appropriately screen for actionable factors in vulnerable populations.

Cure of Congenital Purpura Fulminans via Expression of Engineered Protein C Through Neonatal Genome Editing in Mice.

PC (protein C) is a plasma anticoagulant encoded by PROC; mutation in both PROC alleles results in neonatal purpura fulminans-a fatal systemic thrombotic disorder. In the present study, we aimed to develop a genome editing treatment to cure congenital PC deficiency. We generated an engineered APC (activated PC) to insert a furin-cleaving peptide sequence between light and heavy chains. The engineered PC was expressed in the liver of mice using an adeno-associated virus vector or CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9)-mediated genome editing using an adeno-associated virus vector in vivo. The engineered PC could be released in its activated form and significantly prolonged the plasma coagulation time independent of the cofactor activity of PS (protein S) in vitro. The adeno-associated virus vector-mediated expression of the engineered PC, but not wild-type PC, prolonged coagulation time owing to the inhibition of activated coagulation FV (factor V) in a dose-dependent manner and abolished pathological thrombus formation in vivo in C57BL/6J mice. The insertion of EGFP sequence conjugated with self-cleaving peptide sequence at Alb locus via neonatal in vivo genome editing using adeno-associated virus vector resulted in the expression of EGFP in 7% of liver cells, mainly via homology-directed repair, in mice. Finally, we succeeded in improving the survival of PC-deficient mice by expressing the engineered PC via neonatal genome editing in vivo. These results suggest that the expression of engineered PC via neonatal genome editing is a potential cure for severe congenital PC deficiency.

Brisk walking pace offsets venous thromboembolism risk equivalent to established monogenic mutations.

Mendelian mutations in F2 and F5 genes are known risk factors for venous thromboembolism (VTE). This study aimed to explore the association between walking pace and VTE, compare its risk with Mendelian mutations, and identify if blood biomarkers mediate this effect. We followed 445,261 UK Biobank participants free of VTE at baseline. Walking pace was self-reported, and carrier status for F2 and F5 gene mutations was determined by rs1799963 and rs6025 genotypes. We used a Cox proportional hazard model to estimate walking pace's effect on VTE risk, bidirectional Mendelian randomization (MR) analysis to assess causality, and mediation analysis to explore blood biomarkers. Over a median follow-up of 12.8 years, 11,155 incident VTE cases were identified. The 10-year incidence rates for brisk and slow walking paces were 1.32% and 3.90%, respectively. For F5 carriers, the rates were 1.70% (brisk pace) and 3.62% (slow pace). Brisk walking pace reduced VTE risk in F5 carriers (2.65%) compared to non-carriers with a slow pace (3.66%). MR analysis confirmed a causal relationship from walking pace to VTE risk. Mediation analysis revealed that serum albumin and cystatin C mediated 8.7% to 11.7% of the effect of brisk walking pace on VTE risk. A slow walking pace is causally associated with increased VTE risk. A brisk walking pace mitigates VTE risk, particularly in individuals with F5 gene mutations, and this effect is partially mediated by serum albumin and cystatin C.

Laboratory and Molecular Diagnosis of Factor XI Deficiency.

The prevalence of factor XI (FXI) deficiency is 1 per 10 to 20,000 in the general population, much higher than that reported in most texts. The prevalence is higher in Ashkenazi Jews where it is about 1:20. Clinically, FXI deficiency presents as a mild bleeding disorder mostly associated with posttraumatic or postsurgical hemorrhages or unexplained minor bleeding. It is often discovered due to incidental finding of a prolonged activated partial thromboplastin time (aPTT) on routine laboratory screening. FXI deficiency is an autosomal recessive bleeding disorder with many causative F11 gene defects. Diagnosis is based on FXI activity, antigen levels, and molecular diagnostics. As FXI levels do not correlate with bleeding symptoms, identification of pathogenic genetic variants may be a more accurate predictor of bleeding risk and therefore aid in the clinical management of the patient. Two variants in the F11 gene account for most cases found in the Jewish and Arab populations. Patients with FXI deficiency can develop inhibitors to FXI although spontaneously acquired inhibitors are extremely rare. We will discuss laboratory and molecular assays used to diagnose FXI deficiency as well as interferences that can complicate diagnosis including new anticoagulants and acquired FXI inhibitors.

The History of Rare Bleeding Disorders.

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.

Acquired factor V inhibitor treated with rituximab

Acquired factor V (FV) inhibitors are extremely rare and present with a broad spectrum ranging from asymptomatic laboratory anomalies to life-threatening critical bleeds. The overall rarity along with the heterogeneity of clinical presentations poses a challenge in diagnosis. There is currently no standard of care immunosuppressive therapy (IST) in these settings. Most patients in the literature receive multiple agents, including but not limited to combinations of IST and/or recombinant products.Here, we present a case of a man in his 50s who initially presented with oozing at peripheral IV and tracheostomy sites with intermittent epistaxis. He was later found to have an FV activity level of less than 1% and an FV inhibitor titre of 184 Bethesda units/mL. The patient was initially stabilised with fresh frozen plasma, platelets and tranexamic acid and treated with intravenous immunoglobulin and glucocorticoids. However, this resulted in only mild improvement in his coagulation studies. He was then treated with weekly doses of rituximab for 4 weeks with ongoing glucocorticoids without complications. This adds to the growing literature on rituximab as a possible treatment option for acquired FV inhibitors.

New and de novo Biallelic Variant Associated with Owren’s Disease: Precision Medicine in Coagulation Disorders

Introduction: Coagulation factor V deficiency, also called Owren’s disease or parahemophilia [1], is a genetic disease with an autosomal recessive inheritance pattern that causes moderate to severe bleeding [2]. It can be classified into type I when the deficiency is quantitative and type II when the deficiency is qualitative [3]. Currently, it is associated with variants in the F5 gene. According to recent database searches, 450 clinically significant variants and approximately 3942 variants related to the F5 gene have been identified [2].

Discovery and prioritization of genetic determinants of kidney function in 297,355 individuals from Taiwan and Japan

Current genome-wide association studies (GWAS) for kidney function lack ancestral diversity, limiting the applicability to broader populations. The East-Asian population is especially under-represented, despite having the highest global burden of end-stage kidney disease. We conducted a meta-analysis of multiple GWASs (n = 244,952) on estimated glomerular filtration rate and a replication dataset (n = 27,058) from Taiwan and Japan. This study identified 111 lead SNPs in 97 genomic risk loci. Functional enrichment analyses revealed that variants associated with F12 gene and a missense mutation in ABCG2 may contribute to chronic kidney disease (CKD) through influencing inflammation, coagulation, and urate metabolism pathways. In independent cohorts from Taiwan (n = 25,345) and the United Kingdom (n = 260,245), polygenic risk scores (PRSs) for CKD significantly stratified the risk of CKD (p < 0.0001). Further research is required to evaluate the clinical effectiveness of PRSCKD in the early prevention of kidney disease.

Genome-Wide Search for Nonadditive Allele Effects Identifies PSKH2 as Involved in the Variability of Factor V Activity.

Factor V (FV) is a key molecular player in the coagulation cascade. FV plasma levels have been associated with several human diseases, including thrombosis, bleeding, and diabetic complications. So far, 2 genes have been robustly found through genome-wide association analyses to contribute to the inter-individual variability of plasma FV levels: structural F5 gene and PLXDC2. The authors used the underestimated Brown-Forsythe methodology implemented in the QuickTest software to search for non-additive genetic effects that could contribute to the inter-individual variability of FV plasma activity. QUICKTEST was applied to 4 independent genome-wide association studies studies (LURIC [Ludwigshafen RIsk and Cardiovascular Health Study], MARTHA [Marseille Thrombosis Association], MEGA [Multiple Environmental and Genetic Assessment], and RETROVE [Riesgo de Enfermedad Tromboembolica Venosa]) totaling 4505 participants of European ancestry with measured FV plasma levels. Results obtained in the 4 cohorts were meta-analyzed using a fixed-effect model. Additional analyses involved exploring haplotype and gene×gene interactions in downstream investigations. A genome-wide significant signal at the PSKH2 locus on chr8q21.3 with lead variant rs75463553 with no evidence for heterogeneity across cohorts was observed (P=0.518). Although rs75463553 did not show an association with mean FV levels (P=0.49), it demonstrated a robust significant (P=3.38x10-9) association with the variance of FV plasma levels. Further analyses confirmed the reported association of PSKH2 with neutrophil biology and revealed that rs75463553 likely interacts with two loci, GRIN2A and POM121L12, known for their involvement in smoking biology. This comprehensive approach identifies the role of PSKH2 as a novel molecular player in the genetic regulation of FV, shedding light on the contribution of neutrophils to FV biology.

Gene therapy for hemophilia

Concept Gene therapy with adeno-associated virus (AAV) vectors treats hemophilia A or B by delivering a functional F8 or F9 gene to hepatocytes. This single infusion enables endogenous production of FVIII or FIX protein, reducing bleeding in patients. Evolution Long-term clinical studies have provided insight into the efficacy, safety, and durability of AAV-mediated gene therapies for hemophilia A and B. Gene therapies have now been approved for hemophilia A (valoctocogene roxaparvovec) and hemophilia B (etranacogene dezaparvovec; fidanacogene elaparvovec) in select regions. Application The approved gene therapies are associated with a strong reduction in bleeding tendency and increased FVIII or FIX activity levels, without the need for additional FVIII or FIX replacement therapies, in the vast majority of patients. Future Steps Improvements in AAV technology, protein expression, and immunogenicity may render AAV-mediated gene therapies more efficient, longer lasting and safer for people with hemophilia A or B.

The common VTE-protective G haplotype of F5 increases factor V-short, TFPI function, and risk of bleeding

AbstractThe G haplotype is a group of co-inherited single nucleotide variants in the F5 gene that reduce venous thromboembolism (VTE) risk. Although 7% of the population is homozygous for the G haplotype (F5-G/G), the underlying mechanism of VTE protection is poorly understood. Using RNA sequencing data from 4651 blood donors in the INTERVAL study, we detected a rare excision event at the factor V (FV)-short splice sites in 5% of F5-G/Gs carriers as compared with 2.16% of homozygotes for the F5 reference sequence (F5-ref; P = .003). Highly elevated (∼10-fold) FV-short, an FV isoform that lack most of the B-domain, has been linked with increased tissue factor inhibitor α (TFPIα) levels in rare hemorrhagic diathesis, including East Texas bleeding disorder. To ascertain whether the enhanced FV-short splicing seen in F5-G/G INTERVAL participants translated to increased plasma FV-short levels, we analyzed plasma samples from 7 F5-G/G and 13 F5-ref individuals in a recall-by-genotype study. A ∼2.2-fold higher amount of FV-short was found in a plasma pool from F5-G/G participants when compared with the pool of F5-refs (P = .029), but there was no difference in the total FV levels. Although no significant difference in TFPI levels were found, F5-G/Gs showed a ∼1.4-fold TFPI-dependent increase in lag time to thrombin generation than F5-refs (P = .0085). Finally, in an analysis of 117 699 UK Biobank participants, we discovered that, although being protective against VTE, the G haplotype also confers an increase in bleeding episodes (P = .011). Our study provides evidence that the effect of the common G haplotype is mediated by the FV-short/TFPI pathway.

Clinical and genetic spectrum of factor XII deficiency in the Han population of East China

BackgroundFactor XII (FXII or F12) deficiency is a rare inherited disorder, typically lacking haemorrhagic symptoms. There is limited literature exists on FXII deficiency and mutations within the Chinese population. This study aimed to characterize the spectrum of F12 gene mutations in a Chinese cohort and to investigate the relationship between FXII mutations and clinical phenotypes.MethodsGenetic and clinical data from 51 unrelated probands with FXII deficiency, along with their families, were meticulously collected and analysed.ResultsGenetic analysis revealed that 94.1% of probands carried genetic defects, with 29 mutations pinpointed in the F12 gene. Of these, 18 mutations were previously reported for the first time by our research group, including c.303_304delCA, c.1078G > A, c.1285 C > T, among others. Of the mutations, 17 are missense, constituting 58.6% of the total. Additionally, 11 are deletions or insertions, of which 8 result in frameshifts, while the remaining one is a nonsense mutation. These mutations were predominantly concentrated in two crucial regions: the catalytic domain and the kringle domain. The most frequently observed mutations were c.1681G > A, closely followed by c.1561G > A and c.1078G > A, indicating a dominance among these mutations. Additionally, a prevalent polymorphism at position 46 was observed in the majority of probands, with 47.1% having the 46T/T genotype and 13.7% having the 46 C/T genotype, which may potentially impact FXII activity. The broad spectrum of asymptomatic FXII deficiency observed within the Han population of East China.ConclusionsWe speculate on the potential impact of recurrent mutations on the efficacy of new drugs being developed to target FXII for thrombosis prevention and treatment. Furthermore, it is important to explore their influence on FXII-related pathways beyond the activation of the contact pathway in the coagulation cascade.

From Venom to Vein: Factor VII Activation as a Major Pathophysiological Target for Procoagulant Australian Elapid Snake Venoms.

Australian elapid snake venoms are uniquely procoagulant, utilizing blood clotting enzyme Factor Xa (FXa) as a toxin, which evolved as a basal trait in this clade. The subsequent recruitment of Factor Va (FVa) as a toxin occurred in the last common ancestor of taipans (Oxyuranus species) and brown snakes (Pseudonaja species). Factor II (prothrombin) activation has been stated as the primary mechanism for the lethal coagulopathy, but this hypothesis has never been tested. The additional activation of Factor VII (FVII) by Oxyuranus/Pseudonaja venoms has historically been considered as a minor, unimportant novelty. This study aimed to investigate the significance of toxic FVII activation relative to prothrombin activation by testing a wide taxonomical range of Australian elapid species with procoagulant venoms. The activation of FVII or prothrombin, with and without the Factor Va as a cofactor, was assessed, along with the structural changes involved in these processes. All procoagulant species could activate FVII, establishing this as a basal trait. In contrast, only some lineages could activate prothrombin, indicating that this is a derived trait. For species able to activate both zymogens, Factor VII was consistently more strongly activated than prothrombin. FVa was revealed as an essential cofactor for FVII activation, a mechanism previously undocumented. Species lacking FVa in their venom utilized endogenous plasma FVa to exert this activity. The ability of the human FXa:FVa complex to activate FVII was also revealed as a new feedback loop in the endogenous clotting cascade. Toxin sequence analyses identified structural changes essential for the derived trait of prothrombin activation. This study presents a paradigm shift in understanding how elapid venoms activate coagulation factors, highlighting the critical role of FVII activation in the pathophysiological effects upon the coagulation cascade produced by Australian elapid snake venoms. It also documented the novel use of Factor Va as a cofactor for FVII activation for both venom and endogenous forms of FXa. These findings are crucial for developing better antivenoms and treatments for snakebite victims and have broader implications for drug design and the treatment of coagulation disorders. The research also advances the evolutionary biology knowledge of snake venoms.

Value of Factor V in the diagnosis of early graft dysfunction after liver transplantation: Internal validation.

Primary graft dysfunction is a major early complication following liver transplantation, potentially leading to retransplantation or patient death. Coagulation Factor V (FV) and ALT have emerged as important biomarkers in assessing liver function, yet their role as early predictors of graft loss has not been fully validated. The aim of this study is to conduct an internal validation of published results on the applicability of FV and ALT for diagnosing graft dysfunction and its predictive ability for graft loss within the first 90 days. We conducted a retrospective cohort study including 513 adult recipients from 2012 to 2023 at the Regional University Hospital of Málaga. FV and ALT levels were measured on postoperative day 2, and patients were categorized based on FV <37.5 and ALT >1539. The association with 90-day graft loss was analyzed. Graft loss occurred in 43 patients (8.4%) within the first 90 days. The combination of FV <37.5 and ALT >1539 on postoperative day 2 demonstrated a specificity of 99% and a test efficiency of 94% in predicting graft loss. Patients meeting both criteria had a 74-fold increased risk of graft loss, with most losses occurring within the first week, and a median survival of 4 days. These findings suggest that FV and ALT on postoperative day 2 are reliable early markers for predicting graft loss, enabling risk stratification and guiding critical decisions regarding early retransplantation in the immediate postoperative period.

Reviewing The Latest Treatments for Haemophilia

Abstract: Advancements in haemophilia treatment have been significant in the first 20 years of the 21st century. However, the progress started with the fractionation of plasma in 1946. The first concentrates were developed after discovering FVIII in frozen plasma cryoprecipitate and FIX in the supernatant in the early 1960s, leading to initial attempts at replacement therapy. Unfortunately, due to the lack of screening methods for viral pathogens, people with haemophilia (PWH) received contaminated concentrates, leading to infections with the hepatitis A virus, hepatitis C virus, and human immunodeficiency virus. Thankfully, by 1985, viral screening methods and virucidal techniques were developed, making concentrates safe. The introduction of chromatography steps with monoclonal antibodies in the production process led to increasingly pure products. However, the problem of immunogenicity of administered concentrates persists. The development of alloantibodies against FVIII in a significant percentage of PWH is a serious adverse effect of replacement therapy. The next major advancement came with cloning the F8 and F9 genes, which allowed the production of factor concentrates using recombinant DNA technology. The injected FVIII and FIX molecules have a relatively short circulating half-life in the plasma of people with haemophilia A and B, approximately 12 and 18 hours, respectively. Methods such as conjugating the factor molecule with fragment crystallizable of IgG1, albumin, or adding polyethylene glycol have been applied to prolong the plasma half-life and extend the interval between injections, especially for risk. The next frontier in haemophilia therapy is the development of durable and potentially curative treatments, such as gene addition therapy. Experiments in haemophilia B have shown promising long-lasting responses. However, the results of gene therapy for haemophilia A have not been as remarkable, and the durability of the treatment is yet to be demonstrated. The long-term safety, predictability, durability, and efficacy of gene therapy for haemophilia A and B remain open questions. Currently, only healthy adult PWH has been enrolled in gene therapy clinical trials, and further studies are needed before gene therapy can be widely applied to children and those with pre-existing antibodies against the delivery vector.

RNAi targeting LMAN1-MCFD2 complex promotes anticoagulation in mice.

Combined deficiency of coagulation factor V (FV) and factor VIII (FVIII) is a rare bleeding disease caused by variants in either lectin mannose binding 1 (LMAN1) or multiple coagulation factor deficiency 2 (MCFD2) gene. Reducing the level of FVIII by inhibiting the LMAN1-MCFD2 complex may become a new anticoagulant approach. We aimed to find a new therapeutic option for anticoagulation by RNA interference (RNAi) targeting LMAN1 and MCFD2. siRNA sequences with cross-homology between mice and humans were designed based on LMAN1 or MCFD2 transcripts in NCBI and were screened with the Dual-Luciferase reporter assay. The optimal siRNAs were chemically modified and conjugated with three N-acetylgalactosamine molecules (GalNAc-siRNA), promoting their targeted delivery to the liver. The expression of LMAN1 and MCFD2 in cell lines or mice was examined by RT-qPCR and western blotting. For the mice administered with siRNA, we assessed their coagulation function by measuring APTT and the activity of FVIII factor. After administration, siRNAs GalNAc-LMAN1 and GalNAc-MCFD2 demonstrated effective and persistent LMAN1 and MCFD2 inhibition. 7 days after injection of 3mg/kg GalNAc-LMAN1, the LMAN1 mRNA levels reduced to 19.97% ± 3.78%. MCFD2 mRNA levels reduced to 32.22% ± 13.14% with injection of 3mg/kg GalNAc-MCFD2. After repeated administration, APTT was prolonged and the FVIII activity was remarkably decreased. The tail bleeding test of mice showed that the amount of bleeding in the treated group did not significantly increase compared with the control group. Our study confirms that therapy with RNAi targeting LMAN1-MCFD2 complex is effective and can be considered a viable option for anticoagulation drugs. However, the benefits and potential risk of bleeding in thrombophilic mice model needs to be evaluated.

Clinical validation and application of targeted long-range polymerase chain reaction and long-read sequencing–based analysis for hemophilia: experience from a hemophilia treatment center in China

BackgroundTargeted long-read sequencing (LRS) is expected to comprehensively analyze diverse complex variants in hemophilia A (HA) and hemophilia B (HB) caused by the F8 and F9 genes, respectively. However, its clinical applicability still requires extensive validation. ObjectivesTo evaluate the clinical applicability of targeted LRS-based analysis compared with routine polymerase chain reaction (PCR)–based methods. MethodsGene variants of retrieved subjects were retrospectively and prospectively analyzed. Whole-genome sequencing was performed to further analyze undiagnosed cases. Breakpoints of novel genomic rearrangements were mapped and validated using long-distance PCR and long-range PCR combined with sequencing. ResultsIn total, 122 subjects were retrieved. In retrospective analysis of the 90 HA cases, HA-LRS assay showed consistent results in 84 cases compared with routine methods and characterized 6 large deletions with their exact breakpoints confirmed by further validation in 6 cases (routine methods only presented failure in amplifying the involved exons). In prospective analysis of the 21 HA subjects, 20 variants of F8 were identified in 20 cases. For the remaining HA patient, no duplication/deletion or single-nucleotide variant (SNV)/insertion and deletion (InDel) was found, but a potential recombination involving exons 14 and 21 of F8 was observed by LRS. Whole-genome sequencing analysis and further verification defined a 30 478 base pairs (bp) tandem repeat involving exons 14 to 21 of F8. Among the 11 HB patients, HB-LRS analysis detected 11 SNVs/InDels in F9, consistent with routine methods. ConclusionTargeted LRS-based analysis was efficient and comprehensive in identifying SNVs/InDels and genomic rearrangements of hemophilia genes, especially when we first expanded the panel to include F9. However, further investigation for complex gross rearrangement is still essential.

Clinical, Laboratory, Molecular, and Reproductive Aspects of Combined Deficiency of Factors V and VIII.

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.

Clinical, Laboratory, and Molecular Aspects of Factor V Deficiency.

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.

Protein S contributes to the paradoxical increase in thrombin generation by low-dose dabigatran in the presence of thrombomodulin.

Low dose of dabigatran paradoxically increased thrombin generation through inhibition of protein C activation. Protein S is a co-factor in the activation of protein C. However, the role of protein S in the enhancement of thrombin generation has not been addressed. Firstly, we measured thrombin generation by calibrated automated thrombinography (CAT) and prothrombin fragments 1+2 (F1+2) assays. Secondly, we assessed activated protein C (APC) formation in normal or protein S-deficient plasma spiking with dabigatran. Then, protein C activation was measured. Finally, heavy chain of factor Va (FVa) and its degradation products were detected by western blot. CAT assay showed that 70-141 ng/ml dabigatran paradoxically increased thrombin generation in normal plasma. However, higher concentrations of dabigatran (283 ng/ml) suppressed the level of ETP. F1+2 assay showed the similar results. In protein S-deficient or protein C-deficient plasma, the paradoxical increase in thrombin generation was absent. Level of generated APC was to a similar extent inhibited by dabigatran in normal and protein S-deficient plasma. Low-dose dabigatran inhibited the protein S-dependent inactivation of factor Va. Protein S participated in the paradoxical enhancement of thrombin generation in normal plasma spiking with low concentrations of dabigatran. Increased thrombin generation at low dabigatran can be explained by reduced thrombin-thrombomodulin mediated APC formation and subsequent reduced FVa inactivation that is protein S-dependent.