Coexistence of hypofibrinogenemia and factor V Leiden mutation: is the balance shifted to thrombosis?

Clinical Consequences and Molecular Bases of Low Fibrinogen Levels

The study of inherited fibrinogen disorders, characterized by extensive allelic heterogeneity, allows the association of defined mutations with specific defects providing significant insight into the location of functionally important sites in fibrinogen and fibrin. Since the identification of the first causative mutation for congenital afibrinogenemia, studies have elucidated the underlying molecular pathophysiology of numerous causative mutations leading to fibrinogen deficiency, developed cell-based and animal models to study human fibrinogen disorders, and further explored the clinical consequences of absent, low, or dysfunctional fibrinogen. Since qualitative disorders are addressed by another review in this special issue, this review will focus on quantitative disorders and will discuss their diagnosis, clinical features, molecular bases, and introduce new models to study the phenotypic consequences of fibrinogen deficiency.

Thrombosis in Inherited Fibrinogen Disorders

Although inherited fibrinogen disorders (IFD) are primarily considered to be bleeding disorders, they are associated with a higher thrombotic complication risk than defects in other clotting factors. Managing IFD patients with thrombosis is challenging as anticoagulant treatment may exacerbate the underlying bleeding risk which can be life-threatening. Due to the low prevalence of IFD, there is little information on pathophysiology or optimal treatment of thrombosis in these patients. We searched the literature for cases of thrombosis among IFD patients and identified a total of 128 patient reports. In approximately half of the cases, thromboses were spontaneous, while in the others trauma, surgery, and parturition contributed to the risk. The true mechanism(s) of thrombosis in IFD patients remain to be elucidated. A variety of anticoagulant treatments have been used in the treatment or prevention of thrombosis, sometimes with concurrent fibrinogen replacement therapy. There is no definite evidence that fibrinogen supplementation increases the risk of thrombosis, and it may potentially be effective in the treatment and prevention of both thrombosis and hemorrhage in IFD patients.

Management of congenital quantitative fibrinogen disorders: a Delphi consensus

INTRODUCTION

No evidence-based guidelines for the management of patients suffering from afibrinogenaemia and hypofibrinogenaemia are available.

AIM AND METHOD

The aim of this study was to harmonize patient's care among invited haemophilia experts from Belgium, France and Switzerland. A Delphi-like methodology was used to reach a consensus on: prophylaxis, bleeding, surgery, pregnancy and thrombosis management.

RESULTS

The main final statements are as follows: (i) a secondary fibrinogen prophylaxis should be started after a first life-threatening bleeding in patients with afibrinogenaemia; (ii) during prophylaxis the target trough fibrinogen level should be 0.5 g L^-1 ; (iii) if an adaptation of dosage is required, the frequency of infusions rather than the fibrinogen amount should be modified; (iv) afibrinogenaemic patients undergoing a surgery at high bleeding risk should receive fibrinogen concentrates regardless of the personal or family history of bleeding; (v) moderate hypofibrinogenaemic patients (i.e. ≥0.5 g L^-1 ) without previous bleeding (despite haemostatic challenges) undergoing a surgery at low bleeding risk may not receive fibrinogen concentrates as prophylaxis; (vi) monitoring the trough fibrinogen levels should be performed at least once a month throughout the pregnancy and a foetal growth and placenta development close monitoring by ultrasound is recommended; (vii) fibrinogen replacement should be started concomitantly to the introduction of anticoagulation in afibrinogenaemic patients suffering from a venous thromboembolic event; and (viii) low-molecular-weight heparin is the anticoagulant of choice in case of venous thromboembolism.

CONCLUSION

The results of this initiative should help clinicians in the difficult management of patients with congenital fibrinogen disorders.

Can the phenotype of inherited fibrinogen disorders be predicted?

Congenital fibrinogen disorders are rare diseases affecting either the quantity (afibrinogenaemia and hypofibrinogenaemia) or the quality (dysfibrinogenaemia) or both (hypodysfibrinogenaemia) of fibrinogen. In addition to bleeding, unexpected thrombosis, spontaneous spleen ruptures, painful bone cysts and intrahepatic inclusions can complicate the clinical course of patients with quantitative fibrinogen disorders. Clinical manifestations of dysfibrinogenaemia include absence of symptoms, major bleeding or thrombosis as well as systemic amyloidosis. Although the diagnosis of any type of congenital fibrinogen disorders is usually not too difficult with the help of conventional laboratory tests completed by genetic studies, the correlation between all available tests and the clinical manifestations is more problematic in many cases. Improving accuracy of diagnosis, performing genotype, analysing function of fibrinogen variants and carefully investigating the personal and familial histories may lead to a better assessment of patients' phenotype and therefore help in identifying patients at increased risk of adverse clinical outcomes. This review provides an update of various tests (conventional and global assays, molecular testing, fibrin clot analysis) and clinical features, which may help to better predict the phenotype of the different types of congenital fibrinogen disorders.

Paradoxical bleeding and thrombosis in a patient with afibrinogenemia and fibrinogen Mumbai mutation

OBJECTIVES

Thrombosis is rarely reported in cases of afibrinogenemia and is generally associated with thrombophilia or replacement therapy. Often, it is difficult to predict whether the patients will bleed or whether they are exposed to the risk of thrombosis.

METHODS

We report a patient with afibrinogenemia who presented with complete thrombosis of right hepatic, portal, and splenic veins and who described a lifelong history of bleeding. Direct sequencing of the three fibrinogen genes was performed to identify the mutation.

RESULTS

DNA sequencing showed the presence of a homozygous for G8017A substitution in exon 8 of the fibrinogen β-chain gene, resulting in a G434D missense mutation (Fibrinogen Mumbai).

CONCLUSIONS

Presence of both bleeding and thrombotic manifestations in a patient with afibrinogenemia in the presence of other associated risk factors warrants a very careful individualized approach in the management of patients with afibrinogenemia.