Severe Factor X Deficiency Research Articles

The first reported case of factor X deficiency in a Filipino child – case study

Abstract Factor X (FX) deficiency is an extremely rare inherited bleeding disorder affecting one in 1,000,000 people. According to the most recent published census of the World Hemophilia Federation, to date there is no reported case of FX deficiency in the Philippines. Rare disorders like FX deficiency often go unrecognised or misdiagnosed. Here, we report the first case of FX deficiency in a Filipino child. A two-month-old male child with consanguinity was referred to our hospital due to bleeding episodes. On the third day of life, he had haematomas to the cervical area and upper extremities, and spontaneous bleeding of the umbilical cord was noted. Initial workup showed prolonged PT and aPTT. Factor deficiencies including FVIII and FIX were considered, however assays were normal. At six weeks of age, the child developed convulsions and deteriorating neurologic status. CT scan showed subarachnoid haemorrhage. The child was referred for further workup. Additional assay of clotting factors showed decreased FX activity at less than 1% and he was diagnosed with severe congenital FX deficiency. Following recurrent intracranial bleeding, the child has been observed to have permanent neurological deficit. This case highlights the importance of timely and accurate diagnosis to prevent life-threatening complications and the risk of permanent disability. Despite being an extremely rare disorder, the incidence of FX deficiency is estimated to be higher in populations where consanguineous marriages are common. Awareness of this rare condition must be emphasised. Families may benefit from screening through coagulation studies as well as genetic counselling, especially when planning future pregnancies. The rarity of this condition has not allowed for the establishment of evidence-based management guidelines, with treatment based on limited literature. Despite development of FX-specific clotting factor products, the high cost and limited availability impact their use in low-resource settings.

Characterization of a Missense Mutation in the Catalytic Domain and a Splicing Mutation of Coagulation Factor X Compound Heterozygous in a Chinese Pedigree.

Background: Congenital coagulation factor X (FX) deficiency is a rare bleeding disorder with an incidence of one in one million caused by mutations in the FX-coding gene(F10), leading to abnormal coagulation activity and a tendency for severe hemorrhage. Therefore, identifying mutations in FX is important for diagnosing congenital FX deficiency. Results: Genetic analysis of the proband identified two single-base substitutions: c.794T > C: p.Ile265Thr and c.865 + 5G > A: IVS7 + 5G > A. His FX activity and antigen levels were < 1% and 49.7%, respectively; aPTT and PT were prolonged to 65.3 and 80.5 s, respectively. Bioinformatics analysis predicted the two novel variants to be pathogenic. In-vitro expression study of the missense mutation c.794T > C: p.Ile265Thr showed normal synthesis and secretion. Activation of FXs by RVV, FVII/TF, and FVIII/FIX all showed no obvious difference between the variant and the reference. However, clotting activity by PT and aPTT assays and activity of thrombin generation in a TGA assay all indicated reduced activity of the mutant FX-Ile265Thr compared to FX-WT. Minigene assay showed a normal splicing mode c.865 + 5G > A: IVS7 + 5G > A, which is inconsistent with clinical phenotype. Conclusions: The heterozygous variants c.794T > C: p.Ile265Thr or c.865 + 5G > A: IVS7 + 5G > A indicate mild FX deficiency, but the compound heterozygous mutation of the two causes severe congenital FX deficiency. Genetic analysis of these two mutations may help characterize the bleeding tendency and confirm congenital FX deficiency. In-vitro expression and functional study showed that the low activity of the mutant FX-Ile265Thr is caused by decrease in its enzyme activity rather than self-activation. The minigene assay help us explore possible mechanisms of the splicing mutation. However, more in-depth mechanism research is needed in the future.

A Multicenter, Retrospective Data Collection Study on the Compassionate Use of a Plasma-Derived Factor X Concentrate to Treat Patients with Hereditary Factor X Deficiency

A Multicenter, Retrospective Data Collection Study on the Compassionate Use of a Plasma-Derived Factor X Concentrate to Treat Patients with Hereditary Factor X Deficiency

Occurrence and management of severe bleeding episodes in patients with hereditary factor X deficiency.

Vitamin K–dependent factor X (FX) plays an important role in thrombin formation, and a deficiency in FX can cause impaired coagulation, the severity of which is usually correlated with the degree of deficiency. Due to the critical role that FX plays in the coagulation cascade, FX deficiency is associated with a higher risk of bleeding than deficiencies in other coagulation factors. Patients with the hereditary autosomal‐recessive homozygous form of FX deficiency, which occurs in approximately 1:1,000,000 individuals worldwide, are often diagnosed when they present with spontaneous life‐threatening haemorrhage (most often intracranial haemorrhage) during the first month of life. In addition to central nervous system bleeds, other severe bleeding types experienced by such patients may include umbilical cord bleeding, gastrointestinal or pulmonary haemorrhage, intramuscular haematomas and/or haemarthrosis. Delayed treatment or inadequate replacement of FX may result in developmental delays, musculoskeletal disabilities or death. The high risk of recurrent severe bleeding necessitates prophylactic replacement therapy for many individuals with severe FX deficiency. Available products for replacement therapy include plasma‐derived FX concentrate and prothrombin complex concentrates. Fresh‐frozen plasma may be used when concentrates are not available but is a less efficient means of FX replacement. This article reviews the literature on severe bleeding in individuals with hereditary FX deficiency and discusses current treatment options.

Pediatric split liver transplantation for congenital factor X deficiency: first 10-year follow-up of a case with portal vein stenting

Congenital factor X (FX) deficiency is a rare autosomal-recessive disease that induces bleeding disorder. Herein, we present the 10-year posttransplant course of a pediatric patient who underwent liver transplantation (LT) with portal vein (PV) stenting for correction of severe congenital FX deficiency, with focus on long-term maintenance of coagulation function and patency of PV stenting. A 17-month-old infant with recurrent hemorrhagic episodes due to FX deficiency underwent split LT using a left lateral section graft. The graft-recipient weight ratio was 2.2%. The graft implantation procedures were performed by following the standard pediatric split LT procedure. Nevertheless, a wall stent was inserted due to PV anastomotic stenosis on posttransplant day 1. Graft function recovered slowly because of partial parenchyma infarct, and the patient was discharged at 46 days after LT operation. The FX activity started to increase soon after LT and gradually normalized; the coagulation profiles have been maintained well for the past 10 years. The patient has been doing well for the past 10 years after LT without any episodes of abnormal bleeding. Due to the risk of vascular complications owed to PV stenting, life-long follow-up is mandatory with special attention until attainment of complete physical growth to adolescent and adulthood.

Use of plasma‐derived factor X concentrate in neonates and infants with congenital factor X deficiency

BackgroundCongenital factor X deficiency (FXD) is a rare bleeding disorder that often presents with severe bleeding in the neonatal period. Long‐term prophylaxis with infusions of FX‐containing products is recommended in patients with FXD and a personal or family history of severe bleeding. A plasma‐derived FX concentrate (pdFX) is approved for on‐demand and prophylactic therapy in adults and children with FXD. The safety and efficacy of pdFX has been demonstrated in patients <12 years of age, yet limited data exist regarding its use in infants. Patients/MethodsThis retrospective case series details clinical experience using pdFX in four neonates with moderate and severe FXD across four institutions. Results and ConclusionsAll four patients presented in the first week of life with severe bleeding. Following treatment of the acute bleed, prophylactic pdFX was initiated at an average of 29 days of life and a dose of 69 IU/kg every 48 hours. Incremental recovery (IR) in three infants averaged 1.42 IU/dL per IU/kg (min‐max: 1.06‐1.67 IU/dL per IU/kg). One patient experienced thrombotic complications in the setting of sepsis. After a median follow‐up of 26.5 months, no patient has experienced breakthrough bleeding episodes. Our study supports the use of pdFX in neonates and infants and suggests that higher pdFX dosing of 70 to 80 IU/kg every 48 hours based on the smallest available vial size is feasible. Because of variability in IR, close monitoring of FX activity should be used to guide dosing in this age group.

A Compound Heterozygosis of Two Novel Mutations Causes Factor X Deficiency in a Chinese Pedigree

Background: Mutations in the F10-coding gene can cause factor X (FX) deficiency, leading to abnormal coagulation activity and severe tendency for hemorrhage. Therefore, identifying mutations in F10 is important for diagnosing congenital FX deficiency. Methods: We studied a 63-year-old male patient with FX deficiency and 10 of his family members. Clotting and immunological methods were used to determine activated partial thromboplastin time (aPTT), prothrombin time (PT), thrombin time (TT), fibrinogen levels, FX activity, and FX antigen levels. The platelet count was determined. A mixing study was performed to eliminate the presence of coagulation factor inhibitors and lupus anticoagulant. Mutations were searched using whole-exome sequencing and certified by Sanger sequencing. Results: Genetic analysis of the proband identified two single-base substitutions: c.1085G>A (p.Ser362Asn) and c.1152C>A (p.Tyr384Ter, termination codon, caused by the DNA sequence TAA). His FX activity and antigen levels were 1.7% and 408.53 pg/mL, respectively; aPTT and PT were 52.3 and 48.0 s, respectively. One brother had the same compound heterozygous mutations, and his FX activity and antigen levels were 1.3% and 465.47 pg/mL, respectively; his aPTT and PT were 65.2 and 54.5 s, respectively. His mother, another brother, and one sister were heterozygous for c.1085G>A (p.Ser362Asn), and his daughter and grandson (6 years old) were heterozygous for c.1152C>A (p.Tyr384Ter). Conclusion: The heterozygous variants p.Ser362Asn or p.Tyr384Ter indicate mild FX deficiency, but the compound heterozygous mutation of the two causes severe congenital FX deficiency and bleeding. Genetic analysis of these two mutations may help characterize the bleeding tendency and confirm congenital FX deficiency.

Genotype analysis and identification of novel mutations in a multicentre cohort of patients with hereditary factor X deficiency.

: The objective was to examine the genotypic and phenotypic characteristics of individuals with hereditary factor X deficiency (FXD), a rare autosomal recessive bleeding disorder caused by mutations in the F10 gene located on chromosome 13q34-ter. To date, 149 F10 mutations have been identified as contributory to FXD. Three open-label phase 3 trials enrolled individuals with mild, moderate, or severe FXD. Individuals received plasma-derived factor X concentrate as routine prophylaxis, to treat bleeds, and/or during or after surgery. F10 genotyping was performed (studies 1 and 2) or genotype data was collected at screening (study 3), and identified F10 mutations were compared against the Human Gene Mutation Database to assess novelty. Genotype data were combined to evaluate the number, type, and novelty of the F10 mutations identified. Genotype data were available for 24 of 27 individuals with mild (n = 2), moderate (n = 2), or severe (n = 20) FXD. Analyses identified 22 separate mutations, including 15 missense mutations, 2 deletions, 4 splice site mutations, and 1 nonsense mutation. Sixteen individuals had homozygous mutations; 8 had compound heterozygous mutations. Eleven unique novel mutations (all compound heterozygous) were identified in seven individuals: six missense mutations, three splice site mutations, one exon deletion, and one nonsense mutation. In silico analyses strongly supported the pathogenicity of all novel mutations. The identification of 11 novel F10 mutations provides a substantial contribution to the mutations known to cause FXD.

On-Demand Treatment of Bleeding Episodes in Patients with Hereditary Factor X Deficiency Using a High-Purity Factor X Concentrate: Data from 2 Clinical Trials and a Data-Collection Study

Introduction: Hereditary factor X (FX) deficiency is a rare bleeding disorder characterized by spontaneous joint, mucosal, and muscle bleeds as well as intracranial hemorrhage. Women and girls may also experience menorrhagia. In the past, hereditary FX deficiency has been treated with fresh frozen plasma or a prothrombin complex concentrate, both of which contain variable amounts of FX. Plasma-derived FX (pdFX) is a high-purity FX concentrate approved in the United States for on-demand treatment of patients with hereditary FX deficiency aged 12 years and older and for perioperative management of bleeding in patients with mild hereditary FX deficiency. pdFX is approved in the European Union for treatment and prophylaxis of bleeding episodes as well as perioperative management in patients with hereditary FX deficiency.Objectives: To present efficacy and safety data from 2 phase 3 clinical studies and 1 data-collection study evaluating pdFX for on-demand treatment of bleeds in patients with hereditary FX deficiency.Methods: Results from 2 phase 3 clinical studies and 1 data-collection study of patients with severe (FX activity [FX:C] <1 IU/dL) or moderate (FX:C 1-5 IU/dL) FX deficiency are included. TEN01 was a prospective, open-label, multicenter, nonrandomized study of subjects aged ≥12 years. Bleeds were treated with an initial dose of 25 IU/kg pdFX followed by additional doses as needed. TEN02 was a prospective, open-label, multicenter, nonrandomized study in children less than 12 years old. In TEN01 and TEN02, pdFX efficacy was assessed as excellent, good, poor, or unassessable. TEN05 was a retrospective, multicenter data-collection study in patients of any age who received ≥1 dose of pdFX on a compassionate-use basis. Investigators retrospectively rated pdFX treatment of bleeds as effective (with hemostasis achieved with the expected number of doses for the severity of the bleed), not effective, or unknown. In TEN05, dosing was at the discretion of the investigator. All protocols were approved by each center's local or national independent ethics committee. All subjects provided written informed consent prior to enrollment.Results: A total of 19 subjects were analyzed from the 2 prospective clinical trials; 12 of these subjects were also included in the retrospective data-collection study. Ages ranged from 1 to 58; 16 of 19 patients were aged ≥12 years. FX deficiency was severe in 17 patients and moderate in 2 patients. During the studies, 326 bleeds were reported, with a median of 12 (range 1-59) bleeds per patient in TEN01, 4 (1-5) bleeds per patient in TEN02, and 5.5 (2-26) bleeds per patient in TEN05. Of these 326 bleeds, 270 bleeds in 18 subjects were treated with pdFX and evaluated. Severity was major for 108 bleeds, minor for 116 bleeds, and not rated for 46 bleeds. Reported bleed causes were menorrhagia (n=97), spontaneous (n=93), trauma or injury (n=75), other (n=3), and unknown (n=2). Bleed locations were mucosal (n=117), joint (n=79), muscle (n=38), other (n=30), and unknown (n=6). Most bleeds (n=230, 85.5%) were treated with a single pdFX infusion (the maximum number of infusions for a single bleed was 12). The total factor dose per bleed per subject ranged from 7.92 to 82.0 IU/kg, with a median of 25.0 IU/kg in TEN01, 31.7 IU/kg in TEN02, and 23.8 IU/kg in TEN05. Treatment effectiveness was assessed by investigators as excellent or good in 43 of 44 rated bleeds (97.7%) in TEN01 and TEN02. One was rated poor in TEN01. In TEN05 pdFX was reported as effective in all 79 rated bleeds (100%). In TEN01, 6 adverse events in 2 patients were reported as related or possibly related to pdFX treatment; all were mild or moderate. No adverse events in TEN02 were considered related or possibly related to pdFX treatment, and no adverse drug reactions or safety concerns were reported in TEN05. No thromboembolic events, inhibitor development, or hypersensitivity reactions were reported in the 3 studies.Conclusions: Across 3 studies, pdFX was rated as effective at treating a variety of bleeds in patients with FX deficiency. Only one dose of pdFX was needed to treat most (85.5%) bleeds. At the doses used in these studies, on-demand pdFX treatment was well tolerated in pediatric and adult subjects. DisclosuresHuang:Baxter: Research Funding; Biogen: Research Funding; Pfizer: Research Funding; Novartis: Other: support to attend meeting; Bio Products Laboratory: Other: Study Investigator. Akanezi:Bio Products Laboratory: Employment. Shapiro:BioMarin: Research Funding; Bayer Healthcare: Other: International Network of Pediatric Hemophilia; Genetech: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Daiichi Sankyo: Research Funding; Bio Products Laboratory: Consultancy; Bioverativ, a Sanofi Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kedrion Biopharma: Consultancy, Research Funding; Prometic Life Sciences: Consultancy, Research Funding; Shire: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sangamo Biosciences: Consultancy; Octapharma: Research Funding; OPKO: Research Funding.

Severe Factor X deficiency and successful pregnancy outcome: A rare case

Factor X (FX) is a Vitamin K-dependent, serine protease produced by the liver that serves pivotal role as the first enzyme in the so-called common pathway of coagulation cascade in fibrin formation. Inherited FX deficiency is a rare autosomal recessive bleeding disorder that is found in 1:1,000,000 individuals. Classification of severity is based on FX coagulant activity. Specific FX replacement product is not yet readily available, but fresh frozen plasma (FFP) and prothrombin complex concentrates can be used for treatment of bleeding symptoms and preparation for surgery. Here, we reemphasize the approach to a patient with severe FX deficiency, who had a successful pregnancy outcome through the rationale use of FFP.

A novel Ala275Val mutation in factor X gene influences its structural compatibility and impairs intracellular trafficking and coagulant activity

Factor X (FX) deficiency is an autosomal recessive severe bleeding disorder. Here, we identified a novel homozygous missense mutation (p.Ala275Val) in the F10 gene in a patient with severe FX deficiency. The novel mutation was analyzed by in vitro expression and modeling. Site-directed mutagenesis of FX cDNA was used to introduce the FX Ala275Val mutation, wild-type as well as mutant FX proteins were expressed in HEK293 cells, and subcellular localization experiments were performed. Expression experiments showed that the FX Ala275Val mutation led to a significant reduction in antigen and activity levels in the culture medium. Moreover, compared to the wild-type, mutant FX-Ala275Val was mainly distributed in the endoplasmic reticulum and rarely entered the Golgi apparatus, suggesting a transportation defect for FX from the endoplasmic reticulum to the Golgi apparatus. Molecular modeling analysis indicated that the Ala275 is spatially located to the catalytic triad of FXa, which is composed of His276, Asp322, and Ser419. The Ala to Val substitution may change the conformation of the catalytic pocket and alter protein folding and enzymatic activity. Our findings demonstrated that the Ala275Val substitution is a pathogenic mutation that causes the inherited FX deficiency.

Genotype Analysis of Patients with Hereditary Factor X Deficiency Enrolled in 2 Phase 3 Studies of Pdfx, a New High-Purity Factor X Concentrate

Introduction: Hereditary factor X (FX) deficiency is a rare, autosomal recessive bleeding disorder of variable severity, with an estimated prevalence of 1:500,000 to 1:1,000,000. Like hemophilia A and B, patients with severe FX deficiency commonly present with bleeding into joints, muscles, or mucous membranes. However, unlike the X-linked disorders of hemophilia A and B, hereditary FX deficiency occurs equally in both sexes due to the location of the FX gene (F10) on chromosome 13q34. A novel, high-purity, high-potency, plasma-derived FX concentrate (pdFX) has been developed for replacement therapy in patients with hereditary FX deficiency. This analysis examines the genotypic and phenotypic characteristics of subjects with hereditary FX deficiency enrolled in 2 prospective, open-label, multicenter phase 3 studies of pdFX. Methods: In study 1, subjects aged ≥12 years with moderate or severe FX deficiency (basal plasma FX activity [FX:C] of ≥1 and Results: Study 1 enrolled 16 subjects (aged 12-58 years [mean 27.1 years], 62.5% female) from the United Kingdom (n=3), Spain (n=4), the United States (n=2), Turkey (n=6), and Germany (n=1); two patients had moderate and 14 had severe FX deficiency. Among the 16 subjects, 13 separate mutations were identified, of which 6 were novel. Nine mutations were missense mutations, 2 were deletions, 1 was a nonsense mutation, and 1 was a splice-site mutation. Consistent with the low FX:C of Study 2 enrolled 2 male subjects (ages 55 years [United States] and 59 years [United Kingdom], respectively), both with mild FX deficiency (basal FX:C of 6 and 8 IU/dL, respectively) and compound heterozygous mutations. Of the 4 mutations identified in these 2 patients, 3 were novel. Of the subjects with moderate or severe FX deficiency (study 1), all 6 Turkish subjects had homozygous mutations resulting in an identical amino acid substitution (p.Gly262Asp). Two subjects in Spain and 1 each in the United States and Germany had mutations resulting in an identical amino acid substitution (p.Gly21Arg); one of these Spanish subjects was a compound heterozygote, with an additional missense mutation of p.Cys246Arg, while the other 3 subjects9 mutations were homozygous. Two UK subjects were each homozygous for 2 different missense mutations (p.Phe71Ser and p.Ile451Phe, respectively), and the remaining 4 subjects each had unique compound heterozygous mutations (p.Val298Met and p.Tyr384Leufs*57 [United Kingdom], p.Glu350Lys and p.Gly450Arg [Spain], p.Cys57Phe and c.70+4A>G splice site mutation [Spain], and p.Gln411* and exon 2 deletion [United States], respectively). The basal level of expressed FX protein (FX:Ag) in 1 patient (87 U/dL) was within the normal range (73-127 U/dL), whereas FX:Ag levels in all other patients (range, Each subject with mild FX deficiency (study 2) had unique compound heterozygous mutations (p.Tyr319His and c.71-1G>C splice site mutation [United Kingdom] and p.Cys90Arg and p.Gln416Leu [United States]). Basal FX:Ag levels in these patients (55 and 48 U/dL, respectively) were close to the normal range. Conclusions: In this analysis, 17 separate F10 mutations were identified in 18 subjects with mild to severe hereditary FX deficiency. Of the mutations identified, 9 are novel and have not previously been characterized. Support: Bio Products Laboratory Ltd. Disclosures Mitchell:Viapath: Employment, Other: employee of Viapath, which received funding from Bio Products Laboratory to perform genetic analysis. Kavakli:Baxter: Other: advisory board member and received educational and investigational support; Bayer: Other: advisory board member and received educational and investigational support; Novo Nordisk: Other: advisory board member and received educational and investigational support; Pfizer: Other: advisory board member and received educational and investigational support; Bio Products Laboratory: Other: received educational and investigational support; CSL Behring: Other: received educational and investigational support; Octapharma: Other: received educational and investigational support. Norton:Bio Products Laboratory: Employment. Austin:SOBI: Other: member of advisory board and received educational support; Pfizer: Other: member of advisory board and received educational support; Novo Nordisk: Other: member of advisory board and received educational support; CSL Behring: Other: member of advisory board and received educational support; Bio Products Laboratory: Other: member of advisory board and received educational support; Bayer: Other: member of advisory board and received educational support; Baxter: Other: member of advisory board and received educational support. Off Label Use: ALN-AT3 is an investigational drug for potential treatment of hemophilia. The data represent phase 1 data..

Frequency of the p.Gly262Asp mutation in congenital Factor X deficiency.

Congenital factor X (FX) deficiency is a rare bleeding disorder inherited as an autosomal recessive trait with an incidence of 1:500000-1000000. A total or partial deficiency of FX causes an impairment of clot formation, leading to a haemorrhagic disease, which manifests with bleeding symptoms of different severity, also unprovoked. We analysed the clinical manifestations, laboratory phenotype and genotype in 12 patients from Turkey affected with severe FX deficiency. Prothrombin time (PT), activated partial thromboplastin time (APTT), FX activity (FX:C) and FX antigen level (FX:Ag) were measured, and mutation analysis was performed for all patients. The most frequent bleeding episodes in patients were epistaxis and easy bruising (11/12, 91%), followed by haemarthroses (10/12, 83%). FX:C was <1% in 11 patients, and 4% in one. FX:Ag was reduced in all patients, consistent with type II deficiency. Direct sequencing of the factor X gene (F10) identified two different mutations: the novel 33bp in-frame deletion p.Thr176_Gln186, c.526_558del, which seems to be associated with milder bleeding symptoms and the c.785G>A, p.Gly262Asp missense mutation (previously reported as Gly222Asp), which is associated with severe bleeding symptoms. The p.Gly262Asp missense mutation was identified in 11 of the 12 patients in this study. Previously published cases on the same p.Gly262Asp mutation were Iranian patients originating from the border between Turkey and Iran suggesting that this mutation may be candidate as a good tool for mutational screening analysis in this area.

Molecular basis of the clotting defect in a bleeding patient missing the Asp-185 codon in the factor X gene

Factor X (FX) is a vitamin K-dependent plasma zymogen, which following activation to factor Xa (FXa), converts prothrombin to thrombin in the blood clotting cascade. It was recently demonstrated that a natural variant of FX carrying the Asp-185 deletion (FX-D185del, chymotrypsinogen numbering) was associated with mild bleeding in a patient with severe FX deficiency. In this study, we expressed FX-D185del in mammalian cells and characterized its properties in appropriate kinetic assays in purified systems. We discovered that while the FX variant can be normally activated by physiological activators; both amidolytic and proteolytic activities of the mutant are dramatically impaired. Interestingly, factor Va (FVa) significantly improved the proteolytic defect when the mutant protease was assembled into the prothrombinase complex. Thus, in contrast to >50-fold catalytic defect in the absence of FVa, the variant activated prothrombin with only ~2.5-fold decreased catalytic efficiency in the presence of the cofactor. The FXa variant dramatically lost its susceptibility to inhibition by antithrombin and tissue factor pathway inhibitor, thus exhibiting ~2-3 orders of magnitude lower reactivity with the plasma inhibitors. Further studies revealed that Na+ no longer activates the variant protease, suggesting that the functionally important allosteric linkage between the Na+-binding and the P1-binding sites of the protease has been eliminated. These results suggest that the lower catalytic efficiency of FXa-D185del in the bleeding patient may be partially compensated by the loss of its reactivity with plasma inhibitors, possibly explaining the basis for the paradoxical severe FX deficiency with only mild bleeding tendency for this mutation.

A recurrent Gly43Asp substitution in coagulation Factor X rigidifies its catalytic pocket and impairs catalytic activity and intracellular trafficking

Factor X (FX) deficiency is one of the most severe among recessively inherited coagulation disorders. The homozygous Gly222Asp mutation (Gly43Asp in the chymotrypsinogen numbering) on the FX gene was found in fifteen patients with severe FX deficiency (FX:C <1%). The Gly(43) residue is located at the highly conserved 42-58 residues region shared among all trypsinogen-like proteins. In vitro expression studies showed that the replacement of a neutral Gly by a charged Asp residue into the so-called loop-40 of the FX (comprising residues from 42 to 58) causes an impairment of its catalytic competence as well as a secretion defect. Steady state kinetic studies showed also a severe defect of activation by FVIIa of the FX43Asp. Surprisingly, molecular dynamics studies clearly indicated that the Gly43Asp mutation neither disrupts nor destabilizes the FXa native structure of the catalytic site. Rather, it makes it more rigid, by thickening the H-bonding network around its catalytic site. Altogether, the defects of FX43Asp explain the severe bleeding symptoms in the patients and outline the relevance of the plasticity in the FXa catalytic pocket for maintenance of its catalytic competence.

Molecular defects in the factor X gene caused by novel heterozygous mutations IVS5+1G&gt;A and Asp409del

Factor X (FX) deficiency is a rare autosomal-recessive bleeding disorder caused by diverse mutations in the F10 gene. To investigate the molecular basis of severe FX deficiency in a mildly hemorrhagic patient, variants of the F10 gene were detected by sequencing. A missense mutation was analysed by in vitro expression and modelling analysis, and a splice mutation using ectopic transcript analysis. The levels of activity of FX (FX:C) were <1% in both intrinsic and extrinsic pathway assays and 1.71% in chromogenic assay, the level of FX antigen (FX:Ag) was 53.36% in the proband. Two novel heterozygous mutations (IVS5+1G>A and Asp409del) were identified in the F10 gene. Ectopic transcript expression combined with informative marker (heterozygous Asp409del) analysis of the splice mutation (IVS5+1G>A) revealed and confirmed that the transcript from the mutated allele was absent, likely caused by the nonsense-mediated mRNA decay pathway. In vitro expression analysis showed that the Asp409del mutant led to a loss of enzymatic activity rather than impaired expression. Molecular modelling analysis confirmed that the Asp409del mutant dramatically altered the conformation of the 185-189 loop and impaired binding of the loop to sodium ions (Na(+) ), diminishing the enzymatic activity of FXa. This is the first report to clarify the molecular mechanisms of two naturally occurring F10 gene variants that cause severe FX deficiency.

Successful Liver Transplantation for a Child With Life-Threatening Recurrent Bleeding Episodes Due to Congenital Factor X Deficiency: A Case Report

Factor X (FX) deficiency is a rare, autosomal-recessive coagulation disorder. Diagnosis can be confirmed by a factor X assay. Although fresh frozen plasma and prothrombin complex concentrates have been used as a temporary treatment of bleeding symptoms and preparation for surgery, frequent transfusion has its risk and prothrombin complex is not available in Korea. We report the first pediatric case of successful liver transplantation for the correction of a severe congenital FX deficiency in a child with recurrent life-threatening hemorrhagic episodes.

Severe factor X deficiency in three unrelated Palestinian patients is caused by homozygosity for the mutation c302delG-correlation with thrombin generation and thromboelastometry

Factor X (FX) is one of the vitamin K-dependent serine proteases, which forms the prothrombinase complex converting prothrombin into thrombin. To search for mutations in F10 gene giving rise to severe FX deficiency and to study the contribution of thrombin generation and thromboelastometry as a tool for evaluation of hemostasis. Mutations in the F10 gene were sought by direct sequencing of all the eight exons and intron/exon boundaries. Thrombin generation and thromboelastometry were performed. Three unrelated Palestinian patients had undetectable FX level (<1 U/dl). All patients were found to be homozygous for c302delG, a new frameshift mutation in the F10 gene causing a stop codon at amino acid 73. The mutant allele was not detected among 152 Palestinians analyzed. Thrombin generation was examined in one of the patients 4 days after fresh frozen plasma was applied, when his FX level was 2 U/dl. Minute thrombin generation was observed, as compared to normal thrombin generation in heterozygotes for the mutation and a healthy control. Thromboelastometry revealed prolonged lag phase when patient's platelet-poor plasma and platelet-rich plasma were tested, with a slightly decreased initial clot formation rate, as compared to carriers' and control sample. Genetic analysis disclosed a unique mutation causing a severe phenotype. Thrombin generation assay may serve as a quick tool for confirming severe deficiency until the specific mutation is identified. Thrombin generation can also serve for monitoring and optimizing treatment. The correlation of thromboelastometry assay and severe FX deficiency is less striking.

Systemic AL amyloidosis with acquired factor X deficiency: A study of perioperative bleeding risk and treatment outcomes in 60 patients.

Systemic light-chain (AL) amyloidosis may be associated with acquired factor X (FX) deficiency and optimal management of this coagulopathy is unknown. We reviewed our experience with 60 patients with isolated FX deficiency (< or =50%) due to AL amyloidosis that underwent an invasive procedure between 1975 and 2007. They were classified as having severe (<10%; n = 6), moderate (10-25%; n = 15), or mild (26-50%; n = 39) FX deficiency. The patients underwent a total of 112 procedures, 19 (17%) of which were managed with periprocedural treatment with one or more hemostatic agents. There were complications in 14 (13%) procedures (bleeding = 12, thrombosis = 1, death = 1). Baseline FX level was not predictive of bleeding risk; the only association with postintervention bleeding was central venous catheter placement. However, bleeding complications were relatively infrequent, particularly in patients with mild or moderate FX deficiency undergoing nonvascular procedures. Activated recombinant factor VII might be considered in patients undergoing major surgical procedures, but further experience is needed. Optimal management of AL patients with FX deficiency undergoing invasive procedures remains to be determined.

Perioperative Outcome of Patients with Acquired Factor X Deficiency Associated with AL Amyloidosis: The Mayo Clinic Experience.

Background AL amyloidosis can be associated with coagulopathy due to acquired factor X (FX) deficiency. Published experience, limited to case reports, suggests that infusion of fresh frozen plasma (FFP), platelets, plasma exchange, and vitamin K are of limited hemostatic efficacy for periprocedural management of coagulopathy. Therefore, we reviewed our cumulative experience of managing patients (pt) with FX deficiency due to AL amyloidosis who underwent an invasive procedure.Methods Pt with AL amyloidosis and isolated FX deficiency (≤ 50%), who underwent an invasive procedure between January 1975 and May 2007, were retrospectively identified from institutional databases. We excluded bone marrow biopsies as well as procedures >3 months prior to the diagnosis of FX deficiency. Endpoints of the study were bleeding, thrombosis, and death.Results Sixty-one pt fit the study criteria. They were arbitrarily classified as having severe (<10%; n=6), moderate (10–25%; n=16), or mild (26–50%; n=39) FX deficiency. The pt underwent a total of 115 procedures, 13 (11.3%) of which were considered major procedures and 102 (88.7%) were minor procedures.Major Procedures 13 pt underwent a major procedure; 4 had severe FX deficiency, 2 moderate, and 7 mild. Procedures included splenectomy, colon resection, renal transplant, and others. All 4 of the pt with severe deficiency were treated with hemostatic agents (FFP, plasma exchange, tranexamic acid, danazol, aminocaproic acid, and rFVIIa) in the perioperative period. Two (50%) of these patients had complications: intraabdominal hematoma and death. The death occurred in a patient with splenic rupture and uncontrolled hemorrhage refractory to rFVIIa and FFP. None of the pt with moderate deficiency experienced complications, despite not receiving hemostatic agents. Similarly, 0/7 patients with mild deficiency developed complications (2 received hemostatic agents FFP, platelets, vitamin K, and DDAVP).Minor Procedures All 61 pt underwent a minor procedure; central venous catheter placement was the most common (n=26), followed by EGD with biopsy (n=16) and renal biopsy (n=10). Six pt with severe deficiency underwent 7 minor procedures, 2 (29%) of which were associated with excess bleeding, despite rFVIIa treatment in both cases. An additional 3 procedures were performed with hemostatic agents and were uncomplicated. 2/16 (13%) pt with moderate deficiency had excess bleeding, 1 of whom was treated with rFVIIa and the other was not treated. Two others received perioperative treatment and did not have a complication. There were 7 complications in the 39 patients with mild deficiency (18%), including 1 AV fistula thrombosis after rFVIIa. Five of the patients with a bleeding complication did not receive treatment. One patient with mild deficiency received procoagulants and did not have excess bleeding.Conclusions -This is the largest series examining the perioperative management of pt with FX deficiency due to AL amyloidosis -Complications occurred in 11.3% of procedures, including one death -In this series, there were no clear predictors of bleeding -FX deficiency did not contribute to mortality, with the exception of 1 case -Bleeding risk is relatively infrequent in pt with mild or moderate FX deficiency, particularly with non-vascular procedures -Although optimal management of pt with severe FX deficiency is unclear, options include rhFVIIa +/− FFP and aminocaproic acid in those requiring procoagulant therapy.