Fibrinogen Bonn (p. Arg510Cys) in the Aα-Chain Is Associated with High Risk of Venous Thrombosis.

INTRODUCTION: Inherited dysfibrinogenemia is a qualitative defect of fibrinogen caused by various mutations among three fibrinogen genes. Dysfibrinogenemia can be associated with an increased risk of thrombosis, bleeding, or both. Here, we report a 36-year-old female with dysfibrinogenemia who experienced two successful pregnancies under thromboprophylaxis after cerebral venous sinus thrombosis (CVST). PATIENTS AND METHODS: In addition to plasmatic coagulation tests, fibrinogen genes FGA, FGB, and FGG were screened using direct genomic DNA sequencing. The structural-functional implications of the detected mutation were analyzed in silico. RESULTS: Inherited dysfibrinogenemia was diagnosed in an index patient after CVST in a risk situation. Anticoagulation with warfarin was stopped after 12 months when the first pregnancy was planned. Pregnancy and spontaneous delivery (2020) was uncomplicated. A second pregnancy was interrupted because of acute cytomegalovirus infection and the third pregnancy was successful in 2022. Pregnancies were accompanied by thromboprophylaxis with enoxaparin 40 mg once daily until 6 weeks postpartum. Substitution of fibrinogen has not become necessary in the index patient so far. Genetic analysis revealed a novel missense mutation (p. Arg510Cys) in the FGA gene ("fibrinogen Bonn") in the index patient, as well as an asymptomatic sister, and their father who experienced recurrent pulmonary embolism. Surface exposure of wild-type Arg510 suggested the mutated Cys510 to form nonnative disulfide bonds with surface-exposed reactive cysteines from other plasma proteins like albumin leading to formation of aggregates and impaired fibrinolysis. CONCLUSIONS: Fibrinogen Bonn might be associated with an increased risk of thrombosis, possibly due to impaired polymerization.

Comparison of F13A1 gene mutations in 73 patients treated with recombinant FXIII-A2.

INTRODUCTION: Congenital factor XIII (FXIII) deficiency is a rare, autosomal recessive bleeding disorder usually caused by mutations in the F13A1 gene that produce a severe quantitative (type I) deficiency of the FXIII-A subunit. AIM: To determine the genotypes of patients with severe FXIII-A deficiency treated with recombinant FXIII-A subunit (rFXIII-A2 ) participating in three international efficacy and safety trials. METHODS: We determined the genotypes of 73 patients in total; 32 had already undergone genotype analysis and were known to carry F13A1 mutations that have been previously reported in the literature. Mutation screening was performed in 41 patients with unknown genetic status using direct sequencing. RESULTS: In total, 51 distinct mutations in 73 patients were identified. Two patients showed a phenotype of severe FXIII-A deficiency, despite having heterozygous missense mutations. Two siblings carried a missense mutation in the F13A1 gene (p.Ser296Arg) in combination with a novel, probably polymorphic variant of the F13B gene (p.Ser654Phe). Molecular modelling of five F13A1 novel missense mutations (p.Leu171Phe, p.Glu204Lys, p.Leu276Phe, p.Asp405His and p.Gly411Cys) predicted a damaging effect of these mutations on protein structure. Although five patients treated with rFXIII-A2 had transient, low-titre, non-neutralizing anti-rFXIII antibodies, no patients developed FXIII-neutralizing antibodies (inhibitors). CONCLUSION: The identified mutations are causally implicated in severe FXIII deficiency; however, they do not appear to increase the risk of neutralizing antibody development against rFXIII-A2 .

A novel missense mutation in the FGB gene (p.Gly302Arg) leading to afibrinogenemia. Predicted structure and function consequences.

Afibrinogenemia represents the rarest form of fibrinogen deficiency. Causative missense mutations occur rarely and may improve the understanding of fibrinogen structure and function. PATIENTS AND METHODS: The propositus was a 26-year-old Argentinian with afibrinogenemia. FGA, FGB and FGG exons and flanking regions were screened by sequencing and the mutant protein was analyzed in silico. RESULTS: A novel missense mutation in the FGB gene (Bbeta Gly272Arg, p.Gly302Arg) was identified. In silico analysis revealed its location in a highly conserved region, which preserves the core fold of the C-terminal beta-chain and is important for proper secretion. A substitution by a positively charged large Arg residue in this area would most likely disturb the core fold by additional interactions with adjacent residues (p.Asp291, p.Asp297, p.Asp311), or by forming of non-native interactions with other proteins, thereby hindering the action of molecular chaperones. Both alternatives would disturb the regular secretion of the beta-chain. CONCLUSIONS: The novel missense mutation in the FGB gene causes afibrinogenemia most probably by affecting the secretion of the fibrinogen beta-chain.

Combined coagulation factor VIII and factor IX deficiency (CDF8F9) in a patient from Lithuania.

Haemophilia A (FVIII deficiency) and haemophilia B (FIX deficiency) are X-linked inherited bleeding disorders. It is a very rare event to identify both haemophilias in the same patient. So far, only two families with such combination are reported in the literature worldwide supported by genetic background. PATIENTS AND METHODS: Evaluation of clinical data, determination of FVIII and FIX levels and genetic analysis of F8 and F9 genes by direct sequencing. RESULTS: We report on a patient having severe haemophilia B (FIX:C <1 IU dl-1) and mild haemophilia A (FVIII:C 18 IU dl-1 ). FIX deficiency was known since childhood, whereas mild haemophilia A was confirmed at the age of 42 due to unexpected bleeding complications after dental extraction despite adequate substitution with plasma derived FIX concentrate. F9 gene analysis showed a point mutation in exon 2 (c.223C>T, p.R75X), whereas F8 gene analysis revealed a point mutation in exon 4 (c.545A>C, p.D182A). The mother of the patient was heterozygous for F8 mutation, but not for F9 mutation suggesting a de novo F9 mutation. Accidentally, further family from Germany with mild Haemophilia A was identified to have the same F8 mutation. F8 Haplotype analysis revealed that the p.D182A mutation most likely represents a founder mutation with common ancestors of the German and the Lithuanian family. CONCLUSIONS: Our results confirm the rare event of Haemophilia A and haemophilia B in the same patient originating from two distinct genetic defects in F8 and F9 genes.

Novel point mutation in fibrinogen (Innsbruck; BßArg44Gly). Phenotypic differences compared to another mutation (fibrinogen Nijmegen) at the same position.

This is a report of a novel fibrinogen point mutation (fibrinogen Innsbruck), a C/G point mutation at position 220 of exon two of the fibrinogen Bß-chain leading to BßArg44Gly. The heterozygous mutation was found in a 16-year-old adolescent, hospitalized for the management of juvenile depression, who suffered from multiple epistaxis episodes during his stay at the university hospital in Innsbruck, Austria. Fibrinogen (based on the Clauss method) and fibrinogen antigen levels were highly discrepant (86 vs. 223 mg/dl) with thrombin time and reptilase time being in the respective upper reference ranges. Densitometric analysis of electrophoretic band pattern showed a reduction of α-polymers, indicating an impaired fibrin polymerization. This is in agreement with structural analysis, which showed a disturbance of the flexibility and structure of the region surrounding the fibrinoeptide B cleavage site. Fibrinogen Nijmegen, a mutation at the same position, is causative for thrombosis, whereas fibrinogen Innsbruck appears to lead to a bleeding tendency, illustrating that even mutations at the same position can cause contrary symptoms.

A novel fibrinogen γ chain frameshift deletion (c.637delT) in a patient with hypodysfibrinogenemia associated with thrombosis.

UNLABELLED: Inherited fibrinogen (FG) disorders are rare and result in quantitative or/and qualitative FG deficiency. While the majority of patients with clinically relevant FG deficiencies demonstrate a bleeding phenotype, a subset of patients are at increased risk of thrombosis. PATIENTS AND METHODS: We report a 54-years old man presenting with a thrombophilic phenotype characterized by two episodes of unprovoked venous thrombosis and a deep vein thrombosis several weeks after myocardial infarction. Recently, he developed A. carotis communis thrombosis and died. Coagulation tests were done using standard procedures. FG genes were screened using direct sequencing. Effect on fibrin clot structure was analyzed by scanning electron microscopy (SEM) and FG chain polymerization was analysed using SDS-PAGE. RESULTS: While thrombophilia testing was negative, we found a decreased concentration of clottable FG (126-148 mg/dl) compared to FG antigen (182-194 mg/dl of normal). The thrombin time was slightly prolonged, while aPTT and reptilase time were within the normal range. A novel deletion in FGG gene (c.637delT) resulting in a frameshift and the premature termination of the γ chain at amino acid position p.228 was identified. SDS-PAGE showed a time-shift in γ-γ and α-α cross linking. SEM showed no statistically significant differences between the patient´s and a healthy control´s fibrin clot structure. CONCLUSIONS: In addition to the reduction of FG concentration expected by the nature of the mutation also a functional defect (hypodysfibrinogenemia) was found. Moreover this mutation seems to increase the risk of thrombosis warranting long term anticoagulation possibly in a combination with antiplatelet drugs.

Neoplasm-induced bleeding in inherited, heterozygous FXIII-A deficiency.

UNLABELLED: Inherited mild factor XIII deficiency belongs to one of the most underdiagnosed bleeding disorders so far. This is, because most patients do not develop bleeding complications in daily life. Patient, methods: A man (age: 64 years) without a history of bleeding presented with painful swelling of neck, weight loss, anemia and episodic bleeding from the right tonsil necessitating tonsillectomy. Histologic and immunohistochemical evaluation revealed cytokeratin-positive epitheloid angiosarcoma. Blood coagulation status showed significantly elevated D-dimer and decreased FXIII levels (FXIII-activity 35%, FXIIIA-Ag 16-26%). Plasma mixing studies excluded neutralizing antibodies against FXIII. RESULTS: A novel heterozygous F13A1 gene nonsense mutation (p.Glu103Ter, c.307G>T) was found confirming heterozygous FXIII-A deficiency. The same mutation was detected in two further asymptomatic relatives. For further clinical management the patient was transfused with FXIII-concentrate and showed an adequate increase of FXIII ruling out FXIII deficiency to be induced by increased turnover. Despite this haemostatic management and antifibrinolytic treatment the patient had to undergo several revisions due to delayed, Hb relevant bleeding after cervical lymph nodes extirpation and resection of tonsil. Two chemotherapy cycles with paclitaxel and palliative radiotherapy of the neck area were performed, but the patient died unfortunately two months after diagnosis. CONCLUSIONS: It is a unique case showing the combination of a highly aggressive angiosarcoma and presence of inherited FXIII deficiency. It is also a rare example demonstrating the benefit of FXIII genotyping besides the expected acquired FXIII deficiency possibly due to neoplasm induced increased consumption by elevated crosslinking of fibrin fibers.

Inhibitor development and management in three non-severe haemophilia A patients with T295A variant.

Missense mutations are the most common F8 gene defects among the patients with non-severe haemophilia A. This type of mutation is typically associated with low (5%) inhibitor risk. In the present retrospective study we analysed the clinical data of 16 haemophiliacs with the T295A missense mutation treated at Bonn Haemophilia Centre. In total, three patients developed inhibitors: two patients experienced low-titer and one high-titer inhibitors. Both patients with low titer inhibitors underwent successful ITI. The third patient, at the age of 81, developed initially low-titer inhibitors (3 BU/ml) after rFVIII therapy because of knee surgery. He experienced spontaneous multiple large skin haematomas and haemarthrosis. Immunosuppressive therapy was not applicable because of the infectious origin of discitis (Th3-Th4). Immunoadsorption was performed, but the inhibitor titer increased up to 42 BU/ml nine weeks after termination. A successful treatment of discitis with antibiotics finally allowed a weekly therapy (four times) with rituximab (375 mg/m(2)). This resulted in a decrease of inhibitor titre to 0.7 BU/ml eight weeks after the fourth rituximab application. Patient had endogenous FVIII levels of 3-5%. Twelve months after rituximab therapy (after B cells recovery) he relapsed with low-titer inhibitors and therefore was treated with single rituximab dose (375 mg/m(2)) again. This resulted in his depletion of B cells, measurable endogenous FVIII levels and non measurable inhibitors. This study demonstrated T295A variant to be associated with significantly increased (3/16 patients, 17%) inhibitor development.

Coagulation factor XIII deficiency. Diagnosis, prevalence and management of inherited and acquired forms.

The plasma circulating zymogenic coagulation factor XIII (FXIII) is a protransglutaminase, which upon activation by thrombin and calcium cross-links preformed fibrin clots/fibrinolytic inhibitors making them mechanically stable and less susceptible to fibrinolysis. The zymogenic plasma FXIII molecule is a heterotetramer composed of two catalytic FXIII-A and two protective FXIII-B subunits. Factor XIII deficiency resulting from inherited or acquired causes can result in pathological bleeding episodes. A diverse spectrum of mutations have been reported in the F13A1 and F13B genes which cause inherited severe FXIII deficiency. The inherited severe FXIII deficiency, which is a rare coagulation disorder with a prevalence of 1 in 4 million has been the prime focus of clinical and genetic investigations owing to the severity of the bleeding phenotype associated with it. Recently however, with a growing understanding into the pleiotropic roles of FXIII, the fairly frequent milder form of FXIII deficiency caused by heterozygous mutations has become one of the subjects of investigative research. The acquired form of FXIII deficiency is usually caused by generation of autoantibodies or hyperconsumption in other disease states such as disseminated intravascular coagulation. Here, we update the knowledge about the pathophysiology of factor XIII deficiency and its therapeutic options.

Haemostasis management of massive bleeding.

Trauma-induced coagulopathy (TIC) is a frequent complication of severely injured patients. The etiology of TIC is complex. Contributing factors include overwhelming generation of thrombin and activated protein C, consumption of coagulation factors and platelets, hyperfibrinolysis, and dilution of clotting factors through administration of fluids. In addition, hypothermia and shock-associated metabolic acidosis augment the clotting dysfunctions. The occurrence of TIC has been shown to be an independent risk factor for death after trauma warranting aggressive treatment. On admission to the emergency room patients with massive blood loss should be employed on basis of clinical and diagnostic variables to identify patients at high risk of coagulopathy. Patients at high risk should be treated with tranexamic acid (1 g bolus followed by 1 g/8 h), and critical factor and platelet deficiencies should be corrected by transfusion of factor concentrates and platelet concentrates. In addition, plasma should be administered in a 1:1 ratio with red cells. The use of recombinant factor VIIa should be considered if major bleeding persists despite best-practive use of blood products.

Mutations affecting disulphide bonds contribute to a fairly common prevalence of F13B gene defects: results of a genetic study in 14 families with factor XIII B deficiency.

Severe factor XIII (FXIII) deficiency is a rare autosomal recessive coagulation disorder affecting one in two million individuals. The aim of the present study was to screen for and analyse F13B gene defects in the German population. A total of 150 patients presenting with suspected FXIII deficiency and one patient with severe (homozygous) FXIII deficiency were screened for mutations in F13A and F13B genes. Twenty-five individuals presented with detectable heterozygous mutations, 12 of them in the F13A gene and 13 of them in the F13B gene. We report on the genotype-phenotype correlations of the individuals showing defects in the F13B gene. Direct sequencing revealed 12 unique mutations including seven missense mutations (Cys5Arg, Ile81Asn, Leu116Phe, Val217Ile, Cys316Phe, Val401Glu, Pro428Ser), two splice site mutations (IVS2-1G>C, IVS3-1G>C), two insertions (c.1155_1158dupACTT, c.1959insT) and one in-frame deletion (c.471-473delATT). Two of the missense mutations (Cys5Arg, Cys316Phe) eliminated disulphide bonds (Cys5-Cys56, Cys316-Cys358). Another three missense mutations, (Leu116Phe, Val401Glu, Pro428Ser) were located proximal to other cysteine disulphide bonds, therefore indicating that the region in and around these disulphide bonds is prone to functionally relevant mutations in the FXIII-B subunit. The present study reports on a fairly common prevalence of F13B gene defects in the German population. The regions in and around the cysteine disulphide bonds in the FXIII-B protein may be regions prone to frequent mutations.

Molecular characterization of five Italian families with inherited severe factor XIII deficiency.

Factor XIII (FXIII) deficiency is a very rare (1:2 000 000) severe autosomal recessive bleeding disorder, mostly due to mutations in the coagulation FXIII A-subunit gene. We have studied the molecular basis of FXIII deficiency in five unrelated Italian families. The coding region, intron-exon boundaries and 5'- and 3'-untranslated regions of the FXIII gene encoding the A subunit were amplified and directly sequenced. Candidate mutations were identified in all the patients. Three novel mutations occurred in three patients. These include a novel homozygous deletion of two base pairs (bp) in exon 14 (c.2002-2003 DelCT). This deletion causes a frameshift from Leu667 and the formation of a stop codon at amino acid position 681. The second patient presents a novel homozygous (c.2126 G>A) transition in exon 15, predicting a Ser708Asn in Barrel 2 domain. The third patient is compound heterozygote for two missense mutations, a previously reported Arg260His substitution, and a novel transition in exon 4 (c.560 C>T) predicting a Pro186Leu in the core domain. The remaining two patients have two previously reported mutations: a 4-bp homozygous deletion in exon 11 (c.1392-1395 Del AATT), previously reported to occur in the Vicenza Area, and a homozygous nonsense mutation in exon 8 (c.979 C>T) predicting an Arg326X in the core domain. The novel mutations occurred at amino acid residues highly conserved among different species (pig, monkey, mouse and dog) and were not detected in 110 normal alleles. Structural analysis shows that Pro186Leu mutation leads to the replacement of the rigid proline pyrrolidine ring by the larger and more flexible leucine side chain and Ser708Asn may probably disrupt the hydrogen bond with Ala291.

Phenotype-genotype correlation in eight Polish patients with inherited Factor XIII deficiency: identification of three novel mutations.

Inherited factor XIII (FXIII) deficiency is known as one of the most rare blood coagulation disorder in humans. In the present study, phenotype and genotype of eight FXIII deficient Polish patients from five unrelated families were compared. The patients presented with a severe phenotype demonstrated by a high incidence of intracerebral haemorrhages (seven of eight patients), haemarthrosis (six patients) and bleeding due to trauma (five patients). Introduction of regular substitution with FXIII concentrate prevented spontaneous bleeding in seven patients. In all patients, mutations within the F13A gene have been identified revealing four missense mutations (Arg77Cys, Arg260Cys, Ala378Pro, Gly420Ser), one nonsense mutation (Arg661X), one splice site mutation (IVS5-1 G>A) and one small deletion (c.499-512del). One homozygous large deletion involving exon 15 was detected by failure of PCR product. The corresponding mutations resulted in severely reduced FXIII activity and FXIII A-subunit antigen concentration, while FXIII B-subunit antigen remained normal or mildly decreased. Structural analysis demonstrated that the novel Ala378Pro mutation may cause a disruption of the FXIII catalytic triad leading to a non-functional protein which presumably undergoes premature degradation. In conclusion, the severe phenotype with high incidence of intracranial bleeding and haemarthrosis was in accordance with laboratory findings on FXIII and with severe molecular defects of the F13A gene.

Retrochorionic hematoma in congenital afibrinogenemia: resolution with fibrinogen concentrate infusions.

Without treatment, pregnancies in patients with congenital afibrinogenemia terminate in miscarriage at 5-6 weeks of gestation. Animal model studies have suggested that implantation site bleeding contributes to miscarriage in afibrinogenemia; however, retrochorionic hematoma in human congenital afibrinogenemia has not been previously observed. A patient with congenital afibrinogenemia receiving fibrinogen prophylaxis developed a retrochorionic hematoma in the first trimester. With continuous intensified fibrinogen concentrate replacement the hematoma resolved over 6 weeks, and the patient delivered a healthy infant. Median fibrinogen levels in the first trimester were 48 mg/dL and in second and third trimester 44 mg/dL. Median fibrinogen levels under 60 mg/dL may be adequate to maintain pregnancy in patients with congenital afibrinogenemia, although it is possible that higher levels might reduce the risk of hemorrhagic events.

[Significance of mutation analysis in patients with haemophilia A]. / Bedeutung der Mutationsdiagnostik bei Patienten mit Hämophilie A.

Haemophilia A represents the most frequent hereditary bleeding disorder in humans. The disease is caused by mutations within the factor VIII gene leading to decreased or absent factor VIII activities with a bleeding tendency depending on the degree of factor VIII deficiency. Nowadays, the causative mutations can be routinely detected and have substantially improved diagnostic and understanding of the pathophysiology of haemophilia A. Identification of the gene defects in haemophilic families have enabled fast and save carrier diagnosis. The correlation of the genetic defects with the clinical course revealed that the type of mutation represents the most important genetic predisposing factor for inhibitor formation, the most severe complication of treatment with factor VIII concentrates. Mitigated clinical courses of haemophilia A were shown to be due to special types of mutations or the presence of concomitant thrombophilic mutations. Molecular models of the factor VIII protein allowed to investigate the effects of specific mutations thus giving new insights in the structure/function relationship of the factor VIII molecule. These findings might promote the development of novel recombinant factor VIII concentrates with higher efficacy, longer half life and reduced immunogenicity.

Lithuanian haemophilia A and B registry comprising phenotypic and genotypic data.

Haemophilia represents the most common hereditary severe bleeding disorder in humans. About 100 families with this condition live in Lithuania, one of the Baltic states with a population of 3.7 million. Haemophilia care and genetic counselling are still rendered difficult owing to limited availability of clotting factor concentrate and molecular genetic diagnosis. In the present study, a haemophilia registry, comprising phenotypic and genotypic data of the majority of Lithuanian haemophilia A and B patients, was established. The phenotype includes the degree of severity, factor VIII:C, factor VIII:Ag, factor IX:C, von Willebrand factor and antigen (VWF:RiCoF, vWF:Ag) and inhibitor status. Genotyping of the factor VIII and IX genes was performed using mutation screening methods and direct sequencing. In 61 out of 63 patients with haemophilia A (96.8%) and all eight patients with haemophilia B (100%), the causative mutations could be detected. Nineteen of the factor VIII gene defects and two of the factor IX gene mutations are reported for the first time. Identified mutations allowed direct carrier diagnosis in 83 female relatives revealing 44 carriers, 38 non-carriers and one somatic mosaicism. The information provided by this registry will be helpful for monitoring the treatment of Lithuanian haemophilia patients and also for reliable genetic counselling of the affected families in the future.

Evaluation of DHPLC in the analysis of hemophilia A.

The manifestation of hemophilia A, a common hereditary bleeding disorder in humans, is caused by abnormalities in the factor VIII (FVIII) gene. A wide range of different mutations has been identified and provides the genetic basis for the extensive variability observed in the clinical phenotype. The knowledge of a specific mutation is of great interest as this may facilitate genetic counseling and prediction of the risk of anti-FVIII antibody development, the most serious complication in hemophilia A treatment to date. Due to its considerable size (7.2 kb of the coding sequence, represented by 26 exons), mutation detection in this gene represents a challenge that is only partially met by conventional screening methods such as denaturing gradient gel electrophoresis (DGGE) or single stranded conformational polymorphism (SSCP). These techniques are time consuming, require specific expertise and are limited to detection rates of 70-85%. In contrast, the recently introduced denaturing high performance liquid chromatography (dHPLC) offers a promising new method for a fast and sensitive analysis of PCR-amplified DNA fragments. To test the applicability of dHPLC in the molecular diagnosis of hemophilia A, we first assessed a cohort of 156 patients with previously identified mutations in the FVIII gene. Applying empirically determined exon-specific melting profiles, a total of 150 mutations (96.2%) were readily detected. Five mutations (3.2%) could be identified after temperatures were optimized for the specific nucleotide change. One mutation (0.6%) failed to produce a detectable heteroduplex signal. In a second series, we analyzed 27 hemophiliacs in whom the mutation was not identified after extensive DGGE and chemical mismatch cleavage (CMC) analysis. In 19 of these patients (70.4%), dHPLC facilitated the detection of the disease-associated nucleotide alterations. From these findings we conclude that the dHPLC technology is a highly sensitive method well suited to the molecular analysis of hemophilia A.