Combined life-threatening thromboses and hemorrhages in a patient with afibrinogenemia and antithrombin deficiency

Management of pregnancy and delivery in congenital fibrinogen disorders: communication from the ISTH SSC Subcommittee on Factor XIII and Fibrinogen

Congenital fibrinogen disorders (CFDs) are a heterogeneous group of rare congenital quantitative and/or qualitative fibrinogen deficiencies. The spectrum of molecular anomalies is broad, leading to several subtypes of fibrinogen disorders (ie, afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia, and hypodysfibrinogenemia). Pregnancy in women with CFDs is a high-risk clinical situation, with an increased tendency for miscarriages, bleeding, and thrombosis. Even though it is well established that management of such pregnancies requires a multidisciplinary approach involving specialists (hematologists and maternal/fetal medicine experts with expertise in the management of inherited bleeding disorders), specific guidelines are lacking. In this International Society on Thrombosis and Haemostasis (ISTH) Scientific and Standardization Committee communication, we aim to propose an expert consensus opinion with literature evidence where available on the strategy for management of pregnancy, delivery, and puerperium in CFDs.

Endovascular Treatment for Lower-extremity Arterial Thrombosis in a Patient with Congenital Afibrinogenemia and a History of Bleeding Complications

Congenital afibrinogenemia is a rare autosomal recessive blood disorder that accompanies thrombotic complications and is associated with bleeding tendency. The management of these opposing complications remains a challenge. Endovascular treatment (EVT) for peripheral arterial thrombosis has not been described in previous studies. A 57-year-old man with congenital afibrinogenemia developed back pain and left lower leg pain. The cause of the pain was confirmed to be renal infarction and lower extremity arterial thrombosis by Doppler ultrasound and contrast-enhanced computed tomography. He was treated with EVT for the lower extremity arterial thrombosis, leading to an excellent short-term improvement without bleeding.

Impact of fibrinogen infusion on thrombin generation and fibrin clot structure in patients with inherited afibrinogenemia

INTRODUCTION

Inherited afibrinogenemia is a very rare disease characterized by complete absence of fibrinogen in the circulation and an increased risk in both thrombosis and bleeding. Infusion of fibrinogen concentrate (FC) is the main approach for prevention and management of bleeding; however, it has been reported to carry a thrombotic risk.

METHODS

We investigated the impact of a standard dose (40-100 mg/kg) of FC infusion on the thrombin generation (TG) parameters and the fibrin clot structure formed in plasma samples of patients with afibrinogenemia. Blood samples were collected from 20 patients before (T0) and 1 hour after infusion of FC (T1). TG was studied with Calibrated Automated Thrombography. Fibrin clot structure was assessed with turbidimetry and scanning electron microscopy (SEM).

RESULTS

FC infusions (mean Clauss fibrinogen plasma level 1.21 g/L at T1) led to a statistically significant increase in endogenous thrombin potentials (ETP) (p<0.0001) and thrombin peaks (p=0.02). Nevertheless, when compared to healthy controls, patients' T1 lag times were longer (p=0.002), ETP values were lower (p=0.0003), and thrombin peaks were lower (p<00001). All fibrin polymerization parameters (turbidimetry) obtained at T1 were comparable to those of patients with inherited hypofibrinogenemia matched for fibrinogen plasma levels.

CONCLUSIONS

In summary, fibrinogen infusion with a standard dose of FC increased but did not correct TG and led to formation of fibrin clots similar to those of patients with hypofibrinogenemia. All in all, our results do not support to biological evidence of hypercoagulability induced by FC in patients with afibrinogenemia.

Extension of the Human Fibrinogen Database with Detailed Clinical Information—The αC-Connector Segment

Fibrinogen, an abundant plasma glycoprotein, is involved in the final stage of blood coagulation. Decreased fibrinogen levels, which may be caused by mutations, are manifested mainly in bleeding and thrombotic disorders. Clinically relevant mutations of fibrinogen are listed in the Human Fibrinogen Database. For the αC-connector (amino acids Aα240–410, nascent chain numbering), we have extended this database, with detailed descriptions of the clinical manifestations among members of reported families. This includes the specification of bleeding and thrombotic events and results of coagulation assays. Where available, the impact of a mutation on clotting and fibrinolysis is reported. The collected data show that the Human Fibrinogen Database reports considerably fewer missense and synonymous mutations than the general COSMIC and dbSNP databases. Homozygous nonsense or frameshift mutations in the αC-connector are responsible for most clinically relevant symptoms, while heterozygous mutations are often asymptomatic. Symptomatic subjects suffer from bleeding and, less frequently, from thrombotic events. Miscarriages within the first trimester and prolonged wound healing were reported in a few subjects. All mutations inducing thrombotic phenotypes are located at the identical positions within the consensus sequence of the tandem repeats.

Age and Origin of the Founder Antithrombin Budapest 3 (p.Leu131Phe) Mutation; Its High Prevalence in the Roma Population and Its Association With Cardiovascular Diseases

Background: Antithrombin (AT) is one of the most important regulator of hemostasis. AT Budapest 3 (ATBp3) is a prevalent type II heparin-binding site (IIHBS) deficiency due to founder effect. Thrombosis is a complex disease including arterial (ATE) and venous thrombotic events (VTE) and the Roma population, the largest ethnic minority in Europe has increased susceptibility to these diseases partly due to their unfavorable genetic load. We aimed to calculate the age and origin of ATBp3 and to explore whether the frequency of it is higher in the Roma population as compared with the general population from the corresponding geographical area. We investigated the association of ATBp3 with thrombotic events in well-defined patients' populations in order to refine the recommendation when testing for ATBp3 is useful.

Methods and Results: Prevalence of ATBp3, investigated in large samples (n = 1,000 and 1,185 for general Hungarian and Roma populations, respectively) was considerably high, almost 3%, among Roma and the founder effect was confirmed in their samples, while it was absent in the Hungarian general population. Age of ATBp3—as calculated by analysis of 8 short tandem repeat sequences surrounding SERPINC1—was dated back to XVII Century, when Roma migration in Central and Eastern Europe occurred. In our IIHBS cohort (n = 230), VTE was registered in almost all ATBp3 homozygotes (93%) and in 44% of heterozygotes. ATE occurred with lower frequency in ATBp3 (around 6%); it was rather associated with AT Basel (44%). All patients with ATE were young at the time of diagnosis. Upon investigating consecutive young (<40 years) patients with ATE (n = 92) and VTE (n = 110), the presence of ATBp3 was remarkable.

Conclusions: ATBp3, a 400-year-old founder mutation is prevalent in Roma population and its Roma origin can reasonably be assumed. By the demonstration of the presence of ATBp3 in ATE patients, we draw the attention to consider type IIHBS AT deficiency in the background of not only VTE but also ATE, especially in selected populations as young patients without advanced atherosclerosis. We recommend including the investigation of ATBp3 as part of thrombosis risk assessment and stratification in Roma individuals.

Heterogeneity of congenital afibrinogenemia, from epidemiology to clinical consequences and management

Fibrinogen is a complex protein playing a major role in coagulation. Congenital afibrinogenemia, characterized by the complete absence of fibrinogen, is associated with major hemostatic defects. Even though the clinical course is unpredictable and can be completely different among patients, severe bleeding is the prominent symptom. Patients are also at increased risk of thrombosis and sometimes suffer from spontaneous spleen rupture, bone cysts and defective wound healing. Due to the relative rarity of afibrinogenemia, there are no evidence-based strategies for helping physicians in care of these patients. Fibrinogen supplementation is the keystone to prevent or treat bleeding events. In addition, fibrinogen, a pleiotropic protein with numerous physiological roles in immunity, angiogenesis and tissue repair, is involved in many diseases. Indeed, depletion of fibrinogen in animal models of infections, tumors and neurological diseases has an effect on the clinical course. The consequences for patients with afibrinogenemia still need to be investigated.

Mutations in inherited fibrinogen disorders correlated with clinical features in the Chinese population

Two probands with unknown reasons for low fibrinogen activity were considered to investigate the association between mutations in inherited fibrinogen disorders (IFDs) and clinical features in the Chinese population. A routine coagulation test was conducted on a Sysmex CS5100 coagulation analyzer, and Sanger sequencing was employed to analyze mutations. A PubMed database search through May 2020 was performed to identify relevant studies regarding the congenital fibrinogen disorder epidemic in China. A common heterozygous missense mutation (c.1233G > A p.Arg35His), a novel heterozygous mutation (c.2014T > C p.Trp672Arg), and a novel homozygous mutation (c.16A > G p.Ile6Val) in the FGA gene were identified in two probands with dysfibrinogenemia. The global coagulation screening assay can distinguish four types of IFD, especially a ratio of Fib:Ag/Fib:C equal to 1.5, which can distinguish patients with hypofibrinogenemia from those with hypodysfibrinogenemia. A total of 81 mutations from 76 probands in 45 IFD families have been reported in the Chinese population. Arg35 in FGA and Arg301 in FGG were responsible for IFD in more than half of patients in the Chinese population. It is possible to distinguish four types of IFD by using a global coagulation screening assay. Mutations in FGA, FGB and FGG occur in different functional regions, and Arg changes account for more than 70% of patients with IFD in the Chinese population, especially Arg-Cys, which may be associated with severe clinical symptoms.