Nonsense mutation in exon V of the factor XI gene does not abolish platelet factor XI expression

Factor XI (FXI) is a plasma glycoprotein produced by the liver that plays an essential role in blood coagulation. Individuals deficient in this protein are prone to bleeding following trauma or surgery. Well-washed platelets possess FXI-like activity and FXI antigen that differs in molecular weight from plasma FXI and is associated with FXI mRNA from platelets in which exon V is absent. Some individuals deficient in plasma FXI produce the platelet form of the protein. The molecular basis for the presence of platelet FXI in plasma FXI-deficient patients is unknown. In the current study, to help determine the mechanism for this differential expression, the FXI genotype was determined for three plasma FXI-deficient individuals who express platelet FXI. All three individuals had a nonsense mutation encoding a stop codon in exon V of the FXI gene that would result in a severely truncated polypeptide. An exon V nonsense mutation in the FXI gene combined with the absence of exon V in platelet FXI mRNA provides a plausible mechanism for the differential expression of platelet FXI in plasma FXI-deficient patients.     

A novel mutation that leads to a congenital factor XI deficiency in a Japanese family

We have identified a novel mutation leading to a congenital deficiency of the coagulation factor XI (FXI) in a Japanese family. A propositus was a 42-year-old female patient without bleeding tendency. Coagulant activity and the antigen level of FXI in her plasma were below the detectable range. The nucleotide sequences of the FXI gene of this patient were determined by a direct sequence method established in this study. A novel nonsense mutation (CAA; Gly263 --> TAA; stop) was identified in exon 8 of the FXI gene. Her parents are first cousins, and a polymerase chain reaction-restriction-fragment length polymorphism analysis revealed that her parents were heterozygous at this nucleotide position. This patient inherited mutant alleles from her parents and is homozygous at this nucleotide position. The nonsense mutation in the FXI gene is responsible for her deficiency of FXI.     

Factor XI deficiency in Southern Iran: identification of a novel missense mutation

Factor XI (FXI)-deficiency is a rare coagulation disorder inherited as an autosomal recessive trait, which is most common in Ashkenazi Jews, but also found in other groups like Moslems. We have reviewed for the first time cases of FXI deficiency in southern Iran in order to analyze their mutations related to factor XI, the main clinical and biological features, levels of circulating factor XI, and bleeding history. All 15 exons and exon–intron boundaries of F11 were polymerase chain reaction amplified using sets of primers designed on the basis of the known genomic sequence of the gene. Among bleeding disorder cases, five were FXI-deficient. FXI clotting activity ranged 0.39–16%. All were severely deficient. In all analyzed patients, functional level of FXI was markedly reduced, confirming the diagnosis of quantitative FXI deficiency. Sequencing of F11 identified three mutations: (1) a highly prevalent type II nonsense mutation (Glu117stop) in a homozygous patient, (2) a previously reported missense (Glu547Lys), and (3) novel missense (Gly372Ala) mutation. No causative mutation was found in the sequenced regions of other patients. One novel mutation and two previously described mutations were identified in patients living in southern Iran. No recurrent mutation was found, perhaps because there is a more intense population mixing in southern Iran. Screening a higher number of FXI-deficient patients will also be necessary to reveal the existence of a founder effect for these mutations in the Iranian population.     

Clinical usefulness of desmopressin for prevention of surgical bleeding in patients with symptomatic heterozygous factor XI deficiency

Heterozygous factor XI (FXI) deficiency is sometimes associated with a significant bleeding tendency. Fresh frozen plasma or FXI concentrates are the mainstay of treatment in patients with a clear bleeding history, especially prior to surgery. However, these treatments are not completely free of risk. Furthermore, thrombosis has been reported in patients with FXI deficiency infused with FXI concentrate. No data are available on the possible efficacy of desmopressin in these patients.   Two patients with a clear bleeding history associated with FXI deficiency and no additional haemostatic defects agreed to be treated with desmopressin before carpal tunnel surgery and dental extraction. The reduced basal FXI activity and antigen levels slightly increased after infusion, reaching borderline values. No bleeding was observed after surgical procedures.   Desmopressin treatment seems a reasonable and useful choice in symptomatic, heterozygous FXI-deficient patients, thus reducing the cost of treatment, the risk of transmission of blood-borne viruses, and of thrombosis.     

Survival advantage of coagulation factor XI-deficient mice during peritoneal sepsis

Anticoagulation is a rational approach to the treatment of sepsis-associated consumptive coagulopathy, but its application is limited because of the risk of excessive bleeding. Factor XI (FXI) contributes substantially to pathological blood coagulation (thrombosis), whereas it contributes only modestly to normal hemostasis. We found that FXI-deficient mice have reduced coagulopathy and increased survival relative to FXI-expressing wild-type mice during cecal ligation and puncture-induced acute peritonitis/sepsis. This finding suggests that FXI contributes to coagulopathy and/or inflammation during sepsis and that pharmacologic inhibition of FXI activity may alter the course and outcome of some infections.     

The use of desmopressin in congenital factor XI deficiency: a systematic review

Factor XI (FXI) deficiency is a rare inherited coagulation disorder characterized by infrequent spontaneous bleeding, but increased risk of hemorrhagic complications especially after trauma or surgery. Treatment options for FXI-deficient patients include virus-inactivated fresh frozen plasma, plasma-derived FXI concentrates, and activated recombinant FVII. Inhibitors of fibrinolysis, such as tranexamic acid, and desmopressin (DDAVP) have also been used in these patients, especially in mild cases. The current knowledge on the use of the latter agent in this congenital bleeding condition is systematically reviewed here. Although limited, the available literature data suggest the potential role of DDAVP for either treatment of bleeding episodes or the prevention of postoperative bleeding in patients with milder FXI defects. However, these findings need to be supported by further trials on large population of patients.     

Induction of an inhibitor antibody to factor XI in a patient with severe inherited factor XI deficiency by Rh immune globulin

In this paper, we report an inhibitor antibody to factor XI (FXI) in a woman with severe inherited FXI deficiency, induced by FXI present in an Rh immune globulin preparation. The patient is homozygous for the Glu117Stop mutation, associated with a FXI level of less than 1 U/dL. Unlike all previously described patients with severe FXI deficiency and an inhibitor, the patient had never been exposed to blood products. Following 3 injections of Rh immune globulin during pregnancy, she developed an inhibitor to FXI (8 Bethesda units) that was shown to bind specifically to FXI and inhibit factor IX cleavage by purified FXIa. The administered Rh immune globulin and 2 other similar products were shown to contain FXI. Clinicians should be aware of the potential for immunization of severely FXI-deficient patients by FXI present in Rh immune globulin preparations.     

Eighteen unrelated patients with factor XI deficiency,four novel mutations and a 100% detection rate by denaturing high-performance liquid chromatography

Factor XI (FXI) deficiency is an autosomal bleeding disorder of variable severity. Inheritance is not completely recessive as heterozygotes may display a distinct, if mild, bleeding tendency. Eighteen unrelated FXI-deficient patients were screened blind by fluorescent single-stranded conformation polymorphism (F-SSCP) analysis and denaturing high-performance liquid chromatography (dHPLC). Mutations were detected in 14 of the 18 patients ( approximately 78%) by F-SSCP and in all 18 patients by dHPLC. Dideoxy sequencing confirmed the mutations in all 18 patients: eight of the mutations being novel (four of which were in previously reported patients). This showed dHPLC to be a highly sensitive, reliable technique for mutation screening in heterogeneous disorders.     

Thrombin generation in patients with factor XI deficiency and clinical bleeding risk

Summary. Factor XI (FXI) deficiency is a rare bleeding disorder. Most patients with FXI deficiency are mild bleeders but certain patients with similar FXI activity exhibit different bleeding phenotype. Routine laboratory assays do not help physicians to estimate the individual bleeding risk in these patients. Thrombin generation test (TGT) is a more comprehensive, global function test of the clotting system. We investigated whether or not the bleeding tendency of patients with FXI deficiency is correlated with features of the TGT. Twenty‐four patients with FXI deficiency were divided in two groups: (i) severe bleeders (n = 9) and (ii) mild or non‐bleeders (n = 15). All severe bleeders had a personal history of surgery‐related severe bleeding. Thrombin generation (TG) was measured in platelet‐rich plasma (PRP) using a low concentration of tissue factor 0.5 pm . In patients exhibiting severe bleeding tendency, independently of their FXI level, a dramatically impaired TG was observed. For example, despite a low plasma FXI = 1 IU dl^?1, a clinically non‐bleeding individual exhibited normal TG results whereas another patient with severe bleeding history and FXI = 40 IU dl^–1 had a very low TG capacity. Low velocity and delayed TG were the main parameters suggesting a higher bleeding risk. DNA analysis of patients reported eight novel mutations of the FXI gene but neither mutation location nor secretion or not of the variant correlated with the bleeding tendency. The results of this study suggest that TG measurement in PRP may be a useful tool to predict bleeding risk in FXI deficiency and should be studied further in larger prospective clinical studies.     

Identification of two novel mutations in non-Jewish factor XI deficiency

Summary. We have studied two heterozygous unrelated CRM non-Jewish FXI-deficient patients. Neither of the patients carries a previously described mutation. Their FXI genes were screened by SSCP analysis following PCR amplification of each exon and the flanking intronic sequences. DNA fragments showing aberrant mobility were cloned and sequenced. The following mutations were identified: in case 1, a T to G transition in exon 12 results in the substitution of Phe-442 by Val (FXI-F442V); in case 2 a C to A transition in exon 5 results in the substitution of Cys-128 by a nonsense codon (FXI-C128X). The missense mutation results in a substitution within the protease domain of FXI. Molecular modelling locates this residue in a structurally conserved region of the protease domain and the amino acid substitution may therefore interfere with either chain folding and subsequent secretion or the stability of the protein in plasma. We conclude that the mutations which we have identified are responsible for the inherited abnormality in these patients.     

A variant of von Willebrand''s disease characterized by recessive inheritance and missing triplet structure of von Willebrand factor multimers

A 10-yr-old girl had bleeding symptoms of moderate severity; her mother and maternal aunt had milder bleeding symptoms, and other members of the kindred were asymptomatic. In the child, factor VIII coagulant activity (VIII:C) and von Willebrand factor antigen (vWF:Ag) were normal, ristocetin cofactor very low, and the bleeding time (BT) markedly prolonged. These values were normal in the rest of the kindred, but the mother and maternal aunt had prolonged BT and a high VIII:C/vWF:Ag ratio. Crossed immunoelectrophoresis (CIE) showed a vWF:Ag peak migrating more anodally in the propositus, two distinct peaks, one migrating anodally, in the father, paternal uncle, and grandmother, and normal peaks in the rest of the kindred. In the propositus, analysis of vWF multimers in plasma on 1.6% sodium dodecyl sulfate (SDS) agarose revealed that there were no larger multimers and there was a relative increase of the smallest multimer. This relative increase was also seen in her relatives with a double peak on CIE. Using gels of smaller porosity, each multimer of the propositus's plasma consisted of a single band, instead of the repeating triplet seen in normal and von Willebrand's disease varients types IIA and IIB. The abnormalities found in the propositus are tentatively interpreted as being due to double heterozygosity for two different genes. The defective gene carried by the father affects the triplet structure of vWF multimers, whereas a prolonged BT and a high VII:C/vWF:Ag ratio are the only phenotypic expressions of the defective gene of the mother. The findings of aberrant triplet structure in congenital vWD strengthen the view that this structure is an intrinsic feature of the normal vWF molecule.     

Factor VII R110C: a novel missense mutation (Arg110Cys) in the second epidermal growth factor-like domain causing factor VII deficiency in members of a Japanese family.

This report describes the findings of a genetic analysis of the factor VII (FVII) gene in a Japanese, male patient with FVII deficiency. The proband showed FVII activity level of 25% and FVII antigen level of 28% of the normal value, but he had no severe bleeding episodes. We identified the mutation by direct sequencing of polymerase chain reaction products representing all exons except 1b and their flanking intronic regions of his FVII gene. We detected a single point mutation, a C-->T substitution at nucleotide position 7863 in exon 5, which results in an amino acid replacement of Arg (CGC) to Cys (TGC) at codon 110 in the second epidermal growth factor-like domain. Homozygosity was confirmed in the propositus by loss of a site for the restriction endonuclease Eco47III. Furthermore, his parents, who had moderately reduced levels of factor VII activity and antigen, carried this mutation site as a heterozygote. Although the Arg11O residue is located distal to the tissue factor (TF) in the soluble TF-FVIIa crystal structure, we infer that the replacement of the positively charged and larger Arg residue with a neutral Cys residue may be likely to impair proper folding, resulting in destabilization of the protein structure.     

Factor XI gene mutations in factor XI deficient patients of the Czech Republic

Factor XI (FXI) deficiency is an autosomal inherited coagulation disorder characterized by bleeding symptoms mainly associated with injury or surgery. Although most of the FXI gene mutations in Ashkenazi Jews are represented by the Glu117stop or Phe283Leu mutations, considerable genetic heterogeneity has been reported in other populations. We report here the genotypic characterization of four families with severe inherited FXI deficiency from the Czech Republic. Seven different gene mutations (three novel) were identified, thus, excluding the existence of a major founder effect in this population. Interestingly, both Glu117stop and Phe283Leu were detected once, further demonstrating the occurrence of these mutations also outside the Jewish populations. In conclusion, we confirm that FXI deficiency in non-Jewish populations is because of different gene mutations; however, the presence of the Glu117stop and Phe283Leu mutations suggests that genetic testing in FXI-deficient patients can start with these two point mutations.     

Uneventful Cesarean Delivery with Administration of Factor XI Concentrate in a Patient with Severe Factor XI Deficiency

Factor XI (FXI) is a procoagulant factor and antifibrinolytic agent, and its absence causes a bleeding tendency. FXI deficiency is autosomal in inheritance, with severe FXI deficiency in homozygotes and partial deficiency in heterozygotes. A 24-year-old primigravida with an uneventful pregnancy and no history of bleeding manifestations was admitted to our department at 38 weeks of gestation. Her blood count and serum biochemistry findings were normal except for a coagulation screen, which revealed a prolonged activated partial thromboplastin time (APTT) of 63 seconds (normal range, 24-35 seconds). The measured FXI coagulant activity of 8 IU/dL (reference range, 70-150 IU/dL) established a diagnosis of severe FXI deficiency. The breech presentation of the fetus prompted the decision for cesarean delivery under general anesthesia. We administered a single dose of FXI concentrate (15 IU/kg), which corrected the APTT to 34 seconds. The cesarean delivery was uncomplicated, and postpartum recovery of the mother and her baby was uneventful with no bleeding complications. The finding of an isolated prolonged APTT should prompt obstetricians to consider FXI deficiency. The appropriate use of factor FXI concentrate in managing obstetric patients with FXI deficiency can minimize potential bleeding complications and ensure an optimal outcome for both mother and neonate.     

Successful use of recombinant factor VIIa in a patient with inhibitor secondary to severe factor XI deficiency

Factor XI (FXI) inhibitors are a rare complication of inherited FXI deficiency. We report the successful use of recombinant factor VIIa (FVIIa) in a patient with a high-responding inhibitor undergoing cataract extraction. At the time of surgery there were limited available data on the optimal management of patients with FXI deficiency. A 62-year-old Ashkenazi Jewish woman had a lifelong history of excessive bleeding secondary to severe FXI deficiency (2 U dL-1), and received FXI concentrate (FXI:C) when she underwent a colposuspension procedure. She was subsequently diagnosed with a FXI inhibitor of 16 Bethesda units (BU) when she developed a poor response to FXI:C at the time of total hip replacement. Two months later she was admitted for cataract extraction. The FXI level was < 1 U dL-1 with an inhibitor titre of 48 BU. She received 90 microg kg-1 of FVIIa immediately preoperatively followed by continuous infusion at a rate of 20 microg kg-1 h-1 for 24 h. The cataract extraction was successful and there was no excess bleeding during surgery or in the postoperative period. Mutation analysis of the FXI gene showed that the patient was homozygous for the type II genotype [exon 5, Glu117-->Ter]. The reason for the low prevalence of inhibitor formation in patients with FXI deficiency is unclear but may reflect a number of factors including reporting bias, the rarity of absent circulating FXI:C activity, and the infrequent use of FXI replacement therapy.     

Factor XI deficiency

Factor XI (FXI) deficiency leads to an injury-related bleeding diathesis, which is notable for the variability in the bleeding tendency and the lack of a clear relationship between bleeding and FXI coagulant activity. Bleeding in this disorder occurs especially in areas of high fibrinolytic activity. Although a rare disorder, the frequency of FXI deficiency is high in certain populations, notably persons of Ashkenazi descent and the Basque population of Southern France. In these populations, five mutations of the FXI gene have been identified and a founder effect has been confirmed for three of these. This paper reviews the role of FXI in coagulation and documents factors known to modify the bleeding tendency. Treatment of surgical bleeding in patients with FXI deficiency is reviewed with emphasis on the combined use of recombinant activated factor VII (rFVIIa; NovoSeven®, Novo Nordisk, Bagsvaerd, Denmark) and the antifibrinolytic agent, tranexamic acid.     

Factor XI deficiency: two novel mutations in asymptomatic Italian patients

Summary. Factor XI (FXI) deficiency is a rare bleeding disorder, resulting in a wide range of bleeding manifestations, from asymptomatic bleeding to injury‐related bleeding. To identify mutations in FXI‐deficient patients and to establish a possible relationship between clinical phenotype and genotype, we studied two patients from Southern Italy with FXI deficiency. They were identified by presurgical or routine laboratory screening. None of them showed bleeding. Three different mutations were detected (Glu117Stop, Cys118Arg and Trp497Gly); two of them were novel (Cys118Arg and Trp497Gly). One patient (with severe FXI levels) showed a compound heterozygosity (Glu117Stop with Cys118Arg). Two novel missense mutations were highly conserved among different species. In our patients, bleeding tendency did not appear to be correlated with FXI levels or with a single mutation in heterozygosis. On the other hand, the compound heterozygosis might explain low FXI levels, but it is not associated with bleeding. Our data confirm that a severe FXI deficiency is not necessarily associated with bleeding.     

Severe factor XI deficiency in a Korean woman with a novel missense mutation (Val498Met) and duplication G mutation in exon 13 of the F11 gene

Hereditary factor XI (FXI) deficiency is a rare bleeding disorder inherited in an autosomal recessive manner. The genetic background of FXI deficiency is the mutations in the F11 gene on the chromosome band 4q35. The prevalence is known to be particularly high in Ashkenazi Jews with well documented recurrent mutations; however, founder mutations in F11 have also been reported in non-Jewish patients. In this report, we describe a Korean patient with severe FXI deficiency whose causative mutations were identified by molecular genetic tests. The patient was a 33-year-old pregnant woman. Routine gynecologic workup revealed prolonged activated partial thromboplastin time. Her FXI level was severely decreased at 1% (reference range, 60-140%). Direct sequencing analysis of the F11 gene was performed to identify the causative mutations. The patient was shown to have two different mutations, c.1546 G>A (Val498Met) and c.1560dupG (Tyr503ValfsX32) in the F11 gene. Val498Met is a novel missense mutation, and the Tyr503ValfsX32 mutation was recently reported in a Japanese patient. Both mutations occurred in the exon 13 of F11 and were believed to disrupt the catalytic domain of the FXI protein, leading to severe FXI deficiency. To the best of our knowledge, this is the first genetically confirmed case of severe FXI deficiency in Korea, and more cases are needed to find any signature of founder effect in the Korean population and its potential relationship with other Asian populations.     

Hereditary plasma thromboplastin antecedent (PTA, FXI) deficiency in a Saudi family

A rare case of factor XI (PTA) deficiency was discovered in a Saudi family in the Riyadh area. Nine members of the family were studied. Two were found to have a severe PTA deficiency; levels of factor XI clotting activity were 0.01 i.u./ml and 0.02 i.u./ml respectively. Both plasmas were markedly deficient in factor XI antigen and appeared to be negative for cross-reactive material (CRM-). The parents were first cousins and both were found to have a minor PTA deficiency. Factor XI levels were: mother 0.048 i.u./ml and father 0.33 i.u./ml. Another sibling was found to have a FXI level of 0.47 i.u./ml. Menorrhagia and bleeding for 1 day after tooth extraction were the main bleeding manifestations found in one member with severe PTA deficiency. Clinically this member presented with iron deficiency anaemia. Other family members had no significant history of bleeding tendency. This is the first report of a Saudi Arabian family with PTA deficiency.