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A case of factor XI deficiency has been presented. The patient required 91 units of fresh frozen plasma for hemostasis, which is more vigorous therapy than was to be expected from reviewing the current literature.
We have identified six novel types of mutation that cause factor XI deficiency, an inherited bleeding disorder. Two are point mutations that interfere with the normal splicing of exons in the mRNA and four are point mutations that result in amino acid substitutions. One of these amino acid substitutions (Asp 16-->His) is near the amino terminal end of the protein. The other three amino acid substitutions (Leu 302-->Pro, Thr 304-->Ile, and Glu 323-->Lys) are in the fourth apple domain, a region that mediates dimerization of identical subunits of factor XI. All four amino acid substitutions cause a reduction in the amount of factor XI secreted from cells grown in vitro.
The previously found high gene frequency of hereditary Factor XI deficiency among Ashkenazic Jews, and the risk of bleeding following trauma in this disorder, prompted us to define the population at risk of bleeding and to evaluate the activated partial thromboplastin time (APTT) as a screening test for its detection. The APTT values of 30 patients with severe Factor XI deficiency (0 to 0.14 unit/ml) overlapped only minimally with the APTT of 56 healthy subjects with Factor XI levels greater than 0.5 unit/ml. In contrast, APTT values of partially deficient patients (Factor XI: 0.15 to 0.49 unit/ml) overlapped substantially with the APTT values of the healthy subjects. However, when only subjects at risk of bleeding were considered (Factor XI less than 0.3 unit/ml), the overlap of APTT values was much smaller. The apparent frequency of this population at risk in the general Ashkenazic population was found to be 3.05%. If a cutoff point of an APTT value at the 80th percentile of the normal range is taken for detection of subjects belonging to this group, one will miss only 4.4% of these cases, with confidence limits of 0.1 to 21%.
We investigated an 8-year-old Arab girl with severe factor XI deficiency; one sibling and her father also have severe factor XI deficiency. Her parents and her father's parents are first cousins. Restriction analysis and DNA sequencing excluded the type I, II, III and IV mutations. We demonstrated a previously undescribed C-->A mutation at nucleotide 1254 in exon 11 resulting in a threonine to asparagine (T-->N) substitution at amino acid 386. We postulate that this substitution interferes with folding and secretion of the molecule.
The Glu117stop mutation in the factor XI (FXI) gene is the most common cause of FXI deficiency and might cause the disease either by poor secretion/stability of the truncated protein or by decreased mRNA levels. Platelet- and lymphocyte-derived mRNA from three Glu117stop heterozygotes were analyzed by reverse-transcriptase polymerase chain reaction and sequencing, demonstrating allele-specific reduction of FXI Glu117stop mRNA.
We identified two novel mutations in an asymptomatic 25-year-old Japanese patient with severe factor XI deficiency. Direct sequencing analysis of PCR products from his factor XI gene revealed a G to T transversion in exon 12, resulting in the nonsense mutation (Glu447Stop) and a G insertion in five consecutive guanine nucleotides ((501)Trp(TGG)-(502)Gly(GGG)) in exon 13 that is expected to lead to the substitution of the last 105 amino acids ((503)Tyr-(607)Val) with 32 abnormal amino acid residues ((503)Val-(534)Thr) followed by stop codon. We also demonstrated that two mutations are associated with the separate alleles in this patient, indicating compound heterozygosity for these mutations. Both mutations lead to the disruption of the catalytic domain structure of the FXI molecule and thus are responsible for his deficiency of factor XI.
Factor XI (FXI) deficiency is a rare bleeding disorder, but is known to occur more frequently in a number of well-defined populations. FXI deficiency is most notable for its variable clinical phenotype. The FXI gene is located at the distal end of the long arm of chromosome 4 and encodes a 607 amino acid mature protein, which is a zymogen for a serine protease. Although the serine protease domain is similar to that of many other coagulation factors, the heavy chain differs in that it contains four tandem Apple domains. FXI is also unique in that it exists as a homodimer, with this dimerization appearing essential for normal function. A total of 39 different FXI mutations have been identified to date, affecting both the catalytic and Apple domains. This article will review the molecular genetics of FXI deficiency with particular focus on the implications of these findings for the clinical management of this condition. The potential utility of alternatives to plasma-derived FXI concentrate, such as recombinant factor VIIa (rFVIIa, NovoSeven) will also be explored.
BACKGROUND AND OBJECTIVES: Factor XI (FXI) deficiency is a rare autosomal recessive coagulopathy which is, however, frequent among Ashkenazi Jews. Two mutations, type II (Glu117stop) and type III (Phe283Leu), account for the majority of abnormal alleles in this population. The aim of this study was to analyze the molecular basis of FXI deficiency in six unrelated Italian probands with severe deficiency, a population hitherto largely unexplored. DESIGN AND METHODS: All patients showed unmeasurable functional FXI levels in plasma. Mutational screening was performed by sequencing. Haplotype analysis was performed using intragenic polymorphisms. Expression studies were performed by transient transfection in COS-1 cells. RESULTS: Sequencing identified two novel mutations: a nonsense mutation (Cys118stop) in exon 5 in two probands, and a 6-bp deletion (643-648delATCGAC) in exon 7 in one proband. The Cys118stop is predicted to cause FXI deficiency by a secretion defect and/or by increased mRNA degradation. The 6-bp deletion causes the loss of residues Ile197 and Asp198. There was a remarkable secretion impairment of the deleted FXI protein. In four of the six probands, the type II mutation was found. Haplotype analysis in patients carrying the type II mutation revealed that they share a common haplotype, perhaps derived from a Jewish ancestor. INTERPRETATION AND CONCLUSIONS: The identification and characterization of two novel mutations widen the mutational spectrum of FXI deficiency. Haplotype analysis is compatible with a Jewish origin of the type II mutation. The high occurrence of the type II mutation among Italian patients will be helpful to direct future genetic screenings.
A 9-year-old female Kerry Blue Terrier with postoperative hemorrhage and prolonged activated partial thromboplastin and activated clotting times was determined to have factor XI deficiency. Transfusions of fresh-frozen plasma given on 4 consecutive days transiently returned the values for activated clotting time and plasma factor XI activity to within reference range limits and controlled the hemorrhage. Analysis of data from 10 other factor XI-deficient Kerry Blue Terriers with a tendency for mild posttraumatic or postoperative bleeding was suggestive of an autosomal mode of inheritance, with a mild tendency for posttraumatic or postoperative bleeding in homozygous and heterozygous dogs. Factor XI deficiency is the only contact phase protein defect that causes a bleeding disorder in animals, which can be explained by the fact that thrombin is more efficient than factor XIIa in activating factor XI. Factor XIa plays a key role in sustaining coagulation.
A patient with a lifelong bleeding tendency of moderate severity was found to have both factor XI deficiency and a long bleeding time. There was a significant deficiency of platelet factor 3, but other parameters of platelet function were normal. Infusion studies showed that both fresh plasma and platelet concentrate were required for complete correction of the haemostatic abnormalities, suggesting that these two defects were inherited coincidentally.
In a survey of coagulation, biochemical and hematological parameters in cattle homozygous (deficient), heterozygous (carrier) and non-affected (normal) for Factor XI deficiency, only the Activated Partial Thromboplastin Time (APTT) results correlated with plasma Factor XI activity levels. The APTT results and the thrombokinetics for the deficient animals were markedly different from the results of either the carrier or normal animals. However, the APTT assay was shown not to be sufficiently sensitive to differentiate between the normal and carrier state for the coagulation disorder. Not only was there no statistical difference between the mean APTT results for the normal and carrier animals, but the thrombokinetics for fibrin clot formation for the two groups were also similar.
We experienced a successful surgical case, who was a 16-year-old boy suffered from atrial septal defect with congenital factor XI deficiency. This disorder is an inherited disorder of blood coagulation characterized by a defect of the intrinsic pathway of thrombin formation and a mild to moderate bleeding tendency, but it can result in severe bleeding in surgical procedures. Open heart surgery in this disorders is rare. Preoperatively we prepared 4000 cc of fresh frozen plasma, but operated without using it. It would appear that the possibility of open heart surgery with congenital factor XI deficiency suggest in this case.
BACKGROUND AND OBJECTIVES: In patients with factor XI(FXI) deficiency the bleeding tendency is poorly correlated with plasma factor levels. The purpose of this study was to evaluate whether or not this discrepancy is also present in a large series of patients from Iran, a previously unexplored ethnic group. DESIGN AND METHODS: In 28 FXI - deficient patients bleeding symptoms and their relation to FXI levels were compared with those of 100 patients with factor VIII (FVIII)deficiency (classic hemophilia), matched for severity of factor deficiency. RESULTS: Spontaneous bleeding was definitely less frequentin FXI deficiency than in hemophilia, whereas postoperative and post-traumatic bleeding occurred with comparable frequencies. Among FXI-deficient patients the severity of symptoms was poorly correlated with FXI levels, mildly deficient patients bleeding almost as frequently as those severely deficient. In contrast, in patients with classic hemophilia there was a close relation between the severity of bleeding and degree of FVIII deficiency. INTERPRETATION AND CONCLUSIONS: As in other ethnic groups, in Iranians factor XI deficiency is less severe than classic hemophilia and the bleeding tendency is poorly correlated to plasma factor levels.
To determine the utility of single-stranded conformation polymorphism (SSCP) analysis for screening mutations in the factor XI (fXI) gene, we investigated three patients with heterozygous factor XI deficiency. DNA sequence analysis confirmed three novel mutations; a CGC --> TGC (Arg308Cys) mutation in exon 9, a GCT-->GTT (Ala412Val) mutation in exon 11 and an AGC --> AGA (Ser576Arg) mutation in exon 15. We postulated on the structural implications of these missense mutations. Our results demonstrated that genotypic analysis is a useful tool for conclusive differentiation between heterozygous factor XI deficiency and normal subjects.
A four-generation 25-member kindred with Factor XI:C deficiency is reported. Factor XI:C levels in heterozygotes varied from 15 to 58%, suggesting that Factor XI:C values for homozygote determination should be less than 15%. The frequency of bleeding was not correlated with Factor XI:C levels in this range. Individuals with joint pain had significantly lower Factor XI:C levels than members without joint pain and pain occurred more frequently in frequent bleeders. Lod scores showed no close genetic linkage of Factor XI:C deficiency with blood group MNSs (chromosome 4), complement components Bf and C4B (chromosome 6), or blood group P.
Factor XI deficiency is a relatively common hereditary coagulation disorder manifested generally as diffuse oozing from a surgical site. Dentists may be the first to discover this deficiency and other coagulopathies after simple tooth extraction. A case is reported which illustrates a typical presentation of this disorder. The need for haematological examination and special dental care is discussed.
We describe a 16-year-old girl with malignant fibrous histiocytoma (MFH) of the heart complicated by factor XI deficiency. The preoperative diagnosis was left atrial myxoma. We decided to perform the operation owing to a normal bleeding time. Operative findings suggested a malignant tumor. The patient was a Jehovah's Witness, and extensive excision was not performed because blood transfusion was not allowed. We resected as much of the tumor and left atrial appendage as possible. The pathologic diagnosis was MFH. Excessive bleeding was not observed during the operation. Bleeding time helps to determine whether a surgical procedure is indicated in patients with factor XI deficiency.
Bleeding tendency in factor (F)XI deficiency may result from premature clot lysis due to insufficient thrombin activatable fibrinolysis inhibitor (TAFI) activation. Thrombomodulin (TM), upon binding to thrombin, is capable of modulating TAFI activation. In this study, we investigated the effects of plasma TM on fibrinolysis in FXI-deficient patients. A clot lysis assay showed the defective down-regulation of fibrinolysis in FXI-deficient patients as compared with normal controls. To evaluate the effects of plasma TM on fibrinolysis, a monoclonal anti-TM IgG was preincubated with plasma for 30 min. The presence of anti-TM IgG significantly prolonged the clot lysis times both in the FXI-deficient and normal plasma, indicating that plasma TM stimulated fibrinolysis. Furthermore, the presence of anti-TM IgG not only reduced protein C activation, but also increased thrombin generation and TAFI activation. The profibrinolytic effect of plasma TM was inhibited in the assay by including either a monoclonal anti-TAFI IgG or a specific TAFI inhibitor--carboxypeptidase inhibitor (CPI). Our results indicate that the impaired thrombin generation in FXI-deficient patients leads to the defective down-regulation of fibrinolysis, and that plasma TM stimulates fibrinolysis through APC pathway which inhibits TAFI activation. The profibrinolytic effect of plasma TM may contribute to the bleeding tendency observed in some FXI-deficient patients.