Congenital Fibrinogen Disorders Research Articles

Congenital Hypodysfibrinogenemia due to γ326Cys→Tyr Mutation: Third Ever-Described Case Associated with Recurrent Venous Thrombosis and COVID Vaccine

<b><i>Introduction:</i></b> Congenital fibrinogen disorders are a heterogenous group of fibrinogen defects. <b><i>Case Presentation:</i></b> Here, we describe hypodysfibrinogenemia in a 33-year-old female patient with provoked recurrent deep vein thrombosis (DVT) diagnosed based on decreased functional and antigenic fibrinogen levels with a decreased functional/antigenic fibrinogen ratio. Definitive diagnosis of congenital hypodysfibrinogenemia is done by genotyping using whole-exome sequencing, which identified the γ326Cys→Tyr mutation combined with single-nucleotide polymorphisms: rs2070011 and rs2070018 in FGA and rs1049636 in FGG. Fibrin structure assays showed reduced maximum polymerization rate. The mother of the proband shares the same γ326Cys→Tyr mutation and experienced a provoked DVT. <b><i>Conclusion:</i></b> Our case with DVT is the third ever-described occurrence of the mutation γ326Cys→Tyr that is associated with hypodysfibrinogenemia. The mechanism by which this mutation induces thrombosis remains unknown. Due to the high recurrence risk of thrombosis, the patient was treated with long-term reduced dose of rivaroxaban (10 mg daily) as secondary prophylaxis.

Congenital fibrinogen disorders: a retrospective clinical and genetic analysis of the Prospective Rare Bleeding Disorders Database

AbstractCongenital fibrinogen deficiency (CFD) is a rare bleeding disorder caused by mutations in FGA, FGB, and FGG. We sought to comprehensively characterize patients with CFD using PRO-RBDD (Prospective Rare Bleeding Disorders Database). Clinical phenotypes, laboratory, and genetic features were investigated using retrospective data from the PRO-RBDD. Patients were classified from asymptomatic to grade 3 based on their bleeding severity. In addition, FGA, FGB, and FGG were sequenced to find causative variants. A total of 166 CFD cases from 16 countries were included, of whom 123 (30 afibrinogenemia, 33 hypofibrinogenemia, 55 dysfibrinogenemia, and 5 hypodysfibrinogenemia) were well characterized. Considering the previously established factor activity and antigen level thresholds, bleeding severity was correctly identified in 58% of the cases. The rates of thrombotic events among afibrinogenemic and hypofibrinogenemic patients were relatively similar (11% and 10%, respectively) and surprisingly higher than in dysfibrinogenemic cases. The rate of spontaneous abortions among 68 pregnancies was 31%, including 86% in dysfibrinogenemic women and 14% with hypofibrinogenemia. Eighty-six patients received treatment (69 on-demand and/or 17 on prophylaxis), with fibrinogen concentrates being the most frequently used product. Genetic analysis was available for 91 cases and 41 distinct variants were identified. Hotspot variants (FGG, p.Arg301Cys/His and FGA, p.Arg35Cys/His) were present in 51% of dysfibrinogenemia. Obstetric complications were commonly observed in dysfibrinogenemia. This large multicenter study provided a comprehensive insight into the clinical, laboratory, and genetic history of patients with CFDs. We conclude that bleeding severity grades were in agreement with the established factor activity threshold in nearly half of the cases with quantitative defects.

A novel missense mutation (FGG c.1168G > T) in the gamma chain of fibrinogen causing congenital hypodysfibrinogenemia with bleeding phenotype

BackgroundFibrinogen plays pivotal roles in multiple biological processes. Genetic mutation of the fibrinogen coding genes can result in congenital fibrinogen disorders (CFDs). We identified a novel heterozygous missense mutation, FGG c.1168G > T (NCBI NM_000509.6), and conducted expression studies and functional analyses to explore the influence on fibrinogen synthesis, secretion, and polymerization.MethodsCoagulation tests were performed on the patients to detect the fibrinogen concentration. Whole-exome sequencing (WES) and Sanger sequencing were employed to detect the novel mutation. Recombinant fibrinogen-producing Chinese hamster ovary (CHO) cell lines were built to examine the recombinant fibrinogen synthesis and secretion by western blotting and enzyme-linked immunosorbent assay (ELISA). The functional analysis of fibrinogen was performed by thrombin-catalyzed fibrin polymerization assay. In silico molecular analyses were carried out to elucidate the potential molecular mechanisms.ResultsThe clinical manifestations, medical history, and laboratory tests indicated the diagnosis of hypodysfibrinogenemia with bleeding phenotype in two patients. The WES and Sanger sequencing revealed that they shared the same heterozygous missense mutation, FGG c.1168G > T. In the expression studies and functional analysis, the missense mutation impaired the recombinant fibrinogen's synthesis, secretion, and polymerization. Furthermore, the in silico analyses indicated novel mutation led to the hydrogen bond substitution.ConclusionThe study highlighted that the novel heterozygous missense mutation, FGG c.1168G > T, would change the protein secondary structure, impair the “A: a” interaction, and consequently deteriorate the fibrinogen synthesis, secretion, and polymerization.

Prophylaxis and Treatment of Bleeding or Thrombosis with Fibrinogen Concentrate (Fibryga) in Patients with Congenital Hypofibrinogenemia or Dysfibrinogenemia

Congenital fibrinogen disorders (CFDs) are rare and make up approximately 0.6% of all inherited bleeding disorders. Two subtypes include a quantitative deficiency of fibrinogen, congenital afibrinogenemia (CA), congenital hypofibrinogenemia (CH), and qualitative defect of the fibrinogen molecule, congenital dysfibrinogenemia (CD). Patients with CD may have a thrombotic as well as a hemorrhagic disease phenotype. In the past, fresh frozen plasma or cryoprecipitate were the only options available for treatment and prevention of bleeding in patients with CFD. Today in the US, human plasma-derived concentrates (FIBRYGA, Octapharma, Lachlen, Switzerland, and RiaSTAP, CSL, Melbourne, Australia) are available and considered safe and effective treatment options for CD and CH. Guidelines for the treatment and prevention of bleeding is not established for CFDs, and especially for CD. We present eight clinical cases of patients with hypo- or dysfibrinogenemia that were effectively treated with a pooled, plasma-derived fibrinogen concentrate (FIBRYGA) either prophylactically for elective or urgent surgery, or post-traumatic injury. The mean age of patients treated was 34 years (min-max 8-70 years). Three patients were male and five, female. Four patients had CH and four, CD. FIBRYGA was used to prophylactically treat a total of ten surgical procedures and two post-traumatic events in these patients. Dosing of FIBRYGA was based on the goal peak plasma fibrinogen concentration and the manufacturer's prescribing information, but modified to align with local laboratory reference ranges for the functional fibrinogen test. No acute or delayed infusion reactions (nausea, fever, rigors, headache) and no hypersensitivity reactions were noted. One patient developed two adverse events, one thrombotic and one hemorrhagic. This patient underwent left, above the knee amputation (AKA) and had a complicated postoperative period due to her multiple comorbidities including type 2 diabetes, hypertension, and long standing, poorly-controlled, severe peripheral arterial disease. She presented nineteen days after receiving FIBRGYA with a PE and multiple DVTs. Fifty-nine days later she presented with wound dehiscence and underwent an extensive excisional debridement with postoperative bleeding deemed to be secondary to her strap sliding during surgery and acting as a tourniquet for venous blood flow. For the majority (86%) of our patients described here with CH and CD, FIBRYGA was well tolerated and effective in preventing post procedural or post traumatic bleeding complications. The post procedural bleeding noted in one patient may have been due to inadequate fibrinogen concentration or other comorbid conditions. Further clinical studies are needed to determine the role of FIBRGYA and other HFC in the treatment of patients with CFD, especially those with CD.

Evaluation of Innovative Laboratory Tests to Predict a Thrombotic Phenotype in a Family with Dysfibrinogenemia and a Novel FGG Mutation

Background: Hypodysfibrinogenemia is a rare hereditary fibrinogen disorder characterized by quantitative and qualitative fibrinogen defects. These fibrinogen defects can cause thrombotic and hemorrhagic phenotypes. Unfortunately, predicting the phenotype in a specific patient is often not possible with routine coagulation tests. Aims: To characterize the phenotype and the genetic profile of a family with hypodysfibrinogenemia and to investigate the ability of innovative tests to predict bleeding and/or thrombotic phenotypes in asymptomatic family members. Methods: The proband, a 60-year-old woman with both bleeding and thrombotic complications who is currently on DOAC treatment, and two daughters were referred to our Hemophilia Treatment Center (HTC) for phenotypical and genotypical analysis of a congenital fibrinogen disorder (CFD). Extensive laboratory testing was done, as well as DNA-sequence analysis and molecular modelling. Thrombin generation and microfluidic testing were also performed to investigate their ability in phenotype prediction. Results: Fibrinogen activity and antigen levels led to the diagnosis of dysfibrinogenemia in the proband and hypodysfibrinogenemia in both daughters. In all three cases, the same heterozygous missense mutation in the FGG gene was uncovered. This likely pathogenic mutation leads to the p.(Tyr375Cys) amino acid change. Molecular modeling predicted possible conformational changes or covalent dimerization of the fibrinogen molecule. Thrombin generation was elevated in one daughter. Microfluidic testing showed enhanced fibrin formation in both daughters, regardless of the coagulation trigger. Conclusion: We described a family with hypodysfibrinogenemia in whom a novel heterozygous missense mutation in the FGG gene was found, possibly leading to conformational changes or covalent dimerization of the fibrinogen molecule. Furthermore we showed that microfluidic testing and thrombin generation can indicate a thrombotic phenotype in these patients, not detected with routine coagulation tests.

International council for standardisation in haematology recommendations on fibrinogen assays, thrombin clotting time and related tests in the investigation of bleeding disorders.

This guidance was prepared on behalf of the International Council for Standardisation in Haematology (ICSH) by an international working group of clinicians and scientists. The document focuses on tests and assays used for the assessment of fibrinogen function, particularly in the scenario of bleeding disorders. Thrombin clotting time (TT) is used as a screening test in some laboratories and also has some utility when direct anticoagulants are in use. The Clauss fibrinogen assay remains the method of choice for the assessment of fibrinogen function, but there are some situations where the results may be misleading. Prothrombin time derived fibrinogen assays are frequently used, but should be interpreted with caution; the results are not interchangeable between different methods and fibrinogen can be overestimated in certain clinical scenarios. Viscoelastic point of care methods may be helpful in emergency situations, while Reptilase time (and similar tests) are useful combined with TT in distinguishing heparin contamination of samples (i.e., if an incorrect blood draw is suspected) and the presence of direct thrombin inhibitors. Fibrinogen antigen assays should be used in the investigation of functional fibrinogen abnormalities; fibrinogen antigen and genetic testing are recommended in the confirmation of congenital fibrinogen disorders. The following recommendations for fibrinogen function assessment are based on published literature and expert opinion and should supplement local regulations and standards.

Congenital fibrinogen disorders-Strengthening genotype-phenotype correlations through novel genetic diagnostic tools.

Congenital fibrinogen disorders or CFDs are heterogenous, both in clinical manifestation and array of culprit molecular lesions. Correlations between phenotype and genotype remain poorly defined. This review examines the genetic landscape discovered to date for this rare condition. The question of a possible oligogenic model of inheritance influencing phenotypic heterogeneity is raised, with discussion of the benefits and challenges of sequencing technology used to enhance discovery in this space. Considerable work lies ahead in order to achieve diagnostic and prognostic precision and subsequently provide targeted management to this complex cohort of patients.

Addressing some challenges of congenital fibrinogen disorders in 2023 and beyond

Congenital fibrinogen disorders (CFD) include several types and subtypes of fibrinogen deficiency, resulting from monoallelic or biallelic mutations in one of the three fibrinogen genes. While it is relatively easy to make an accurate diagnosis based on activity and antigen levels of fibrinogen and genotype, prediction of the clinical phenotype is challenging. Even among patients with the same genotype, the clinical features are heterogeneous and unpredictable. The development of next-generation sequencing rises the possibility to integrate genetic modifiers to explain the subtle relationship between genotype and clinical phenotype. A recent development in integrative hemostasis assays can also help in the determination of patients at risk of bleeding or thrombosis. In this short review, we go through these topics and explain why CFD could be considered an oligogenic rather than a monogenic disease.

Hypodysfibrinogenemia: a diagnostic challenge

Congenital fibrinogen disorders are caused by genetic mutations in the fibrinogen molecule. These result in a qualitative and/or quantitative range of disorders that can demonstrate diverse clinical outcomes for the patient. This presentation of a 41-year-old asymptomatic female gave initially undetectable results for a routine coagulation screen, which in some cases, could have led to potential misdiagnosis. Additional testing in a central laboratory using a range of techniques including light transmittable and electromechanical methods was required to provide accurate fibrinogen determination. Immunological analysis of fibrinogen levels revealed a diagnosis of hypodysfibrinogenemia. This case highlights a diagnostic challenge, especially in regional laboratory setting where often only a single fibrinogen determination method is available. This also demonstrates the role of a central laboratory to support and confirm initial diagnosis by using multiple analysis methods.

Planning Pregnancy and Birth in Women with Inherited Bleeding Disorders.

Inherited bleeding disorders are characterized by a diverse clinical phenotype within and across specific diagnoses. von Willebrand disease (VWD), hemophilia A, and hemophilia B comprise 95 to 97% of inherited bleeding disorders, with the remaining 3 to 5% attributed to rare bleeding disorders, including congenital fibrinogen disorders, factor deficiencies (affecting FII, FV, FV + FVIII, FVII, FX, FXI, and FXIII), and platelet function defects. The pregnancy, birth, and the puerperium may be adversely influenced in the setting of an inherited bleeding disorder depending on its type and clinical phenotype. Obstetric hemostatic challenges may sometimes also unmask the presence of a previously unknown inherited bleeding disorder. This review aims to address the approach to pregnancy and birth in the context of an inherited bleeding disorder and highlights the significance of multidisciplinary input into the care of these women.

A series of Polish patients with congenital fibrinogen disorders: 2 new mutations in fibrinogen gamma chain, Fibrinogen Kostrzyn and Fibrinogen Łódź II.

A series of Polish patients with congenital fibrinogen disorders: 2 new mutations in fibrinogen gamma chain, Fibrinogen Kostrzyn and Fibrinogen Łódź II.

Heterogeneity of Genotype-Phenotype in Congenital Hypofibrinogenemia-A Review of Case Reports Associated with Bleeding and Thrombosis.

Congenital fibrinogen disorders are diseases associated with a bleeding tendency; however, there are also reports of thrombotic events. Fibrinogen plays a role in the pathogenesis of thrombosis due to altered plasma concentrations or modifications to fibrinogen’s structural properties, which affect clot permeability, resistance to lysis, and its stiffness. Several distinct types of genetic change and pathogenetic mechanism have been described in patients with bleeding and a thrombotic phenotype, including mutations affecting synthesis or processing in three fibrinogen genes. In this paper, we focused on familial hypofibrinogenemia, a rare inherited quantitative fibrinogen disorder characterized by decreased fibrinogen levels with a high phenotypic heterogeneity. To begin, we briefly review the basic information regarding fibrinogen’s structure, its function, and the clinical consequences of low fibrinogen levels. Thereafter, we introduce 15 case reports with various gene mutations derived from the fibrinogen mutation database GFHT (French Study Group on Hemostasis and Thrombosis), which are associated with congenital hypofibrinogenemia with both bleeding and thrombosis. Predicting clinical presentations based on genotype data is difficult. Genotype–phenotype correlations would be of help to better understand the pathologic properties of this rare disease and to provide a valuable tool for the identification of patients who are not only at risk of bleeding, but also at risk of a thrombotic event.

Mutations Accounting for Congenital Fibrinogen Disorders: An Update.

Fibrinogen is a complex protein that plays a key role in the blood clotting process. It is a hexamer composed of two copies of three distinct chains: Aα, Bβ, and γ encoded by three genes, FGA, FGB, and FGG, clustered on the long arm of chromosome 4. Congenital fibrinogen disorders (CFDs) are divided into qualitative deficiencies (dysfibrinogenemia, hypodysfibrinogenemia) in which the mutant fibrinogen molecule is present in the circulation and quantitative deficiencies (afibrinogenemia, hypofibrinogenemia) with no mutant molecule present in the bloodstream. Phenotypic manifestations are variable, patients may be asymptomatic, or suffer from bleeding or thrombosis. Causative mutations can occur in any of the three fibrinogen genes and can affect one or both alleles. Given the large number of studies reporting on novel causative mutations for CFDs since the review on the same topic published in 2016, we performed an extensive search of the literature and list here 120 additional mutations described in both quantitative and qualitative disorders. The visualization of causative single nucleotide variations placed on the coding sequences of FGA, FGB, and FGG reveals important structure function insight for several domains of the fibrinogen molecule.

Kongenitalna afibrinogenemija kod novorođenčeta

Introduction: Congenital afibrinogenemia is a rare coagulation disorder characterized by a deficiency in the fibrinogen molecule. Fibrinogen is a hexameric glycoprotein consisting of a polypeptide chain encoded by FGB, FGA, and FGG and is required for normal hemostasis. Changes in FGA, FGB, and FGG may affect fibrinogen at different levels. As a result of these changes, fibrinogen cannot be detected in the blood. Clinical manifestations of such changes range from asymptomatic to life-threatening bleeding or thromboembolic events. Since it is an autosomal recessive disease, the risk is higher in children whose parents are related. Therefore, the disease is more common in regions where consanguineous marriage rates are high. Diagnosis is made by laboratory tests that show the absence of fibrinogen. These patients need to be treated with fibrinogen replacement therapy. Case presentation: This study reports the case of a newborn with congenital afibrinogenemia. The baby born from a first-degree consanguineous marriage was referred to our hospital due to bleeding and ecchymosis, and afibrinogenemia was diagnosed after coagulation tests were performed. Blood samples of the patient and his parents were sent to the Genetic Diseases Diagnosis Center for a genetic diagnosis of afibrinogenemia. A new homozygous mutation of FGB exon 7: c.1220c > t (p.t407 m) (p.thr407 met) was identified in the patient. The patients' parents were heterozygous for the same mutation. Prophylaxis was not recommended for our patient who was asymptomatic in the follow-up. Conclusions: We present the case of a hemorrhagic neonatal patient diagnosed with congenital afibrinogenemia and emphasize that fibrinogen testing should be included in the evaluation of such patients. Furthermore, congenital fibrinogen disorders may be more severe when caused due to unknown specific mutation genes. Therefore, a more center-involved genetic analysis is required to identify undiagnosed fibrinogen and fibrinogen mutations.

Congenital Afibrinogenemia and Hypofibrinogenemia: Laboratory and Genetic Testing in Rare Bleeding Disorders with Life-Threatening Clinical Manifestations and Challenging Management.

Congenital fibrinogen disorders are rare pathologies of the hemostasis, comprising quantitative (afibrinogenemia, hypofibrinogenemia) and qualitative (dysfibrinogenemia and hypodysfibrinogenemia) disorders. The clinical phenotype is highly heterogeneous, being associated with bleeding, thrombosis, or absence of symptoms. Afibrinogenemia and hypofibrinogenemia are the consequence of mutations in the homozygous, heterozygous, or compound heterozygous state in one of three genes encoding the fibrinogen chains, which can affect the synthesis, assembly, intracellular processing, stability, or secretion of fibrinogen. In addition to standard coagulation tests depending on the formation of fibrin, diagnostics also includes global coagulation assays, which are effective in monitoring the management of replacement therapy. Genetic testing is a key point for confirming the clinical diagnosis. The identification of the precise genetic mutations of congenital fibrinogen disorders is of value to permit early testing of other at risk persons and better understand the correlation between clinical phenotype and genotype. Management of patients with afibrinogenemia is particularly challenging since there are no data from evidence-based medicine studies. Fibrinogen concentrate is used to treat bleeding, whereas for the treatment of thrombotic complications, administered low-molecular-weight heparin is most often. This review deals with updated information about afibrinogenemia and hypofibrinogenemia, contributing to the early diagnosis and effective treatment of these disorders.

Dealing with hypodysfibrinogenemia during pregnancy with a successful outcome

Background: Fibrinogen is a protein playing pleiotropic role in human body. It is engaged in maintaining hemostasis. Congenital fibrinogen disorders comprise quantitative and qualitative fibrinogen anomalies. The symptoms range from bleeding, thrombosis to asymptomatic at all what is the most common case. Hypodysfibrinogenemia with lower level of fibrinogen of reduced activity, is the least common of all congenital fibrinogen disorders.
 Case report: A 31-year-old woman was reported at the 21 weeks of gestation, suffered from genital tract bleeding and there was a history of stillbirth. Clinical examination with no pathology, however laboratory tests revealed coagulation abnormalities due to prolonged thrombin test, decreased protein S and lower fibrinogen level (70 mg/dl). Autoimmune diseases were excluded and the diagnosis was widened with rotational thromboelastometry and genetic test for hypodysfibrinogenemia. The patient was treated with fibrinogen substitution and prophylactic dose of heparin throughout pregnancy and 2 weeks following labour. At 39 week of gestation Caesarean section was done, with no complications.
 Results: Genetic test revealed heterozygous mutation in fibrinogen gamma gene confirming hypodysfibrinogenemia. Due to bleeding manifestation in this patient of congenital fibrinogen disorders, fibrinogen substitution was implemented with heparin as a paranticoagulant prophylaxis, what turned out to be successful and enabled the patient to maintain the pregnancy.
 Conclusions: As hypodysfibrinogenemia symptoms are diverse the management is difficult and each patient’s therapy should be planned separately. Pregnancy may be the first time when congenital fibrinogen disorders reveal and it is especially challenging to prevent from obstetrical complications.

Clinical features and genetic defect in six index patients with congenital fibrinogen disorders: Three novel mutations with one common mutation in Taiwan's population.

Congenital fibrinogen disorders (CFDs) are caused by mutations in fibrinogen-encoding genes, FGA, FGB, and FGG, which lead to quantitative or qualitative abnormalities of fibrinogen. Although the diagnosis of CFDs is based on antigenic and functional level of fibrinogen, few genotypes are clearly correlated with phenotype. In this study, we investigated all of the referred patients diagnosed as CFDs in Taiwan's population between 1995 and 2020. Clinical features, laboratory data and genetic defects were analysed. Functional fibrinogen level was determined by the Clauss method. Antigenic fibrinogen was measured by an enzyme-linked immunosorbent assay. Fibrinogen genes were assessed for mutations by polymerase chain reaction and sequencing. A total of 18 patients from six unrelated families with CFDs were identified. One patient from a consanguineous family was diagnosed as afibrinogenemia type 1A with a novel homozygous frameshift mutation in FGB exon 4. The other five (83.3 %) index patients were all diagnosed as dysfibrinogenemia type 3A caused by two novel and one known mutation. Six (33.3 %) patients from three families had a novel mutation in FGB exon 8. The clinical features and laboratory data were highly variable among these patients with the same mutation. Three novel mutations of CFDs causing afibrinogenemia and dysfibrinogenemia were identified. The point mutation in FGB exon 8 is also a common mutation in Taiwan's population. Considerable phenotypic variability among the patients with an identical mutation was observed.

Automated screening procedure for the phenotypes of congenital fibrinogen disorders using novel parameters, |min1|c and Ac/|min1|c, obtained from clot waveform analysis using the Clauss method

IntroductionFibrinogen activity (Ac) is widely measured, but fibrinogen antigen (Ag) is measured only in specialized laboratories, so it is difficult to discriminate congenital fibrinogen disorders (CFDs) from acquired hypofibrinogenemia (aHypo). In this study, to screen for CFD phenotypes we adopted novel parameters, |min1|c and Ac/ |min1|c, and compared these with validated Ac, Ag, and Ac/Ag, and previously proposed Ac/dH and Ac/|min1|. Materials and MethodsWe calibrated |min1| using a CN-6000 instrument and investigated the correlation between Ag and |min1|c for aHypo (n = 131) and CFD [18 dysfibrinogenemia (Dys), two hypodysfibrinogenemia (Hypodys) and four hypofibrinpogenemia (Hypo)]. Furthermore, we proposed a schema for screening CFD phenotypes using |min1|c and Ac/|min1|c. ResultsThe |min1|c correlated well with Ag in aHypo, and Ac/|min1|c was a better parameter for screening Dys and Hypodys than Ac/dH and Ac/|min1|. With the combination of |min1|c and Ac/|min1|c parameters, 15 Dys, 2 Hypodys and four Hypo were categorized in agreement with the phenotype determined using Ag and Ac/Ag; conversely three Dys were classified as one Hypodys (AαR16C) and two Hypo (BβG15C). ConclusionWe demonstrated that |min1|c and Ac/|min1|c are valuable parameters for screening CFD patients and phenotypes in laboratories that do not measure Ag or perform genetic analysis.

An FGA Frameshift Variant Associated with Afibrinogenemia in Dachshunds.

Congenital fibrinogen disorders are very rare in dogs. Cases of afibrinogenemia have been reported in Bernese Mountain, Bichon Frise, Cocker Spaniel, Collie, Lhasa Apso, Viszla, and St. Bernard dogs. In the present study, we examined four miniature wire-haired Dachshunds with afibrinogenemia and ascertained their pedigree. Homozygosity mapping and a genome-wide association study identified a candidate genomic region at 50,188,932–64,187,680 bp on CFA15 harboring FGB (fibrinogen beta chain), FGA (fibrinogen alpha chain), and FGG (fibrinogen gamma-B chain). Sanger sequencing of all three fibrinogen genes in two cases and validation of the FGA-associated mutation (FGA:g.6296delT, NC_006597.3:g.52240694delA, rs1152388481) in pedigree members showed a perfect co-segregation with afibrinogenemia-affected phenotypes, obligate carriers, and healthy animals. In addition, the rs1152388481 variant was validated in 393 Dachshunds and samples from 33 other dog breeds. The rs1152388481 variant is predicted to modify the protein sequence of both FGA transcripts (FGA201:p.Ile486Met and FGA-202:p.Ile555Met) leading to proteins truncated by 306 amino acids. The present data provide evidence for a novel FGA truncating frameshift mutation that is very likely to explain the cases of severe bleeding due to afibrinogenemia in a Dachshund family. This mutation has already been spread in Dachshunds through carriers before cases were ascertained. Genetic testing allows selective breeding to prevent afibrinogenemia-affected puppies in the future.

[Analysis of gene mutation spectrum and pharmacokinetics of fibrinogen infusion in 146 cases of congenital fibrinogen disorders].

目的探讨先天性纤维蛋白原病的基因突变类型与分型、临床表现、实验室检查、诊断及纤维蛋白原替代治疗情况。方法对2003年4月至2020年11月就诊于中国医学科学院血液病医院的146例先天性纤维蛋白原病患者进行回顾性分析。结果146例患者中，男61例（41.8％），女85例（58.2％），就诊时中位年龄为33.5岁；共采集到98例患者的临床症状学信息，34例（34.7％）因出血症状而就诊，33例（33.7％）因手术前检查而确诊，55例（56.1％）患者至少有1次出血，42例（42.9％）无出血表现。纤维蛋白原活性（FIB∶C）与ISTH-BAT出血评分之间呈负相关（rs＝−0.412，P<0.001）。在56例患者中检出34种基因突变（包括新突变16种），其中84.1％为错义突变，FGA外显子2和FGG外显子8突变占全部突变位点的71.4％。无纤维蛋白原血症患者（7例）中位年龄为2（1～12）岁，ISTH-BAT评分为4分；异常纤维蛋白原血症患者（50例）中位凝血酶时间为28.5（19.2～36.6）s。输注纤维蛋白原后1 h、24 h的活性回收率（IVR）分别为（127.19±44.03）％、（101.78±43.98）％。输注纤维蛋白原后，FIB∶C明显提升，凝血酶时间及凝血酶原时间明显下降，用药24 h后凝血酶时间较基线平均下降（15.2±12.1）％。结论多数先天性纤维蛋白原缺乏症患者症状轻微或无症状；无纤维蛋白原血症患者出血症状较为严重，FIB∶C与出血程度之间存在负相关；基因检测有助于疾病分型诊断；FIB∶C/纤维蛋白原抗原（FIB∶Ag）比值<0.7可作为临床分型依据。凝血酶时间可作为异常纤维蛋白原血症诊断及纤维蛋白原替代治疗的疗效判定依据。