Rare congenital bleeding disorders

Clinical, Laboratory, and Molecular Aspects of Factor V Deficiency

Factor V (FV) is a glycoprotein that plays a pivotal role in hemostasis, being involved in coagulant and anticoagulant pathways. Congenital FV deficiency is a rare bleeding disorder with an incidence of 1 per million live births, considering the most severe homozygous form. FV deficiency is diagnosed using routine coagulation tests and FV activity assays. Several mutations, including missense, nonsense, and frameshift, have been detected in the F5 gene. Clinical symptoms are variable, ranging from mild ecchymoses and mucosal bleeding to life-threatening intracranial hemorrhage. The mainstay of treatment includes fresh-frozen plasma, preferentially virus-inactivated. In this narrative review, we provide an update of the main laboratory, molecular, clinical, and therapeutic features of inherited FV deficiency.

Characterization of zebrafish coagulation cofactors Fviii and Fv mutants and modeling hemophilia A and factor V deficiency

The aim of this study is to characterize zebrafish coagulation cofactors fviii and fv mutant fish and assess if they phenocopy classical hemophilia A and factor V deficiency in humans. The embryos from fviii and fv zebrafish heterozygote mutants generated by ENU mutagenesis were purchased from the ZIRC repository. They were reared to adulthood and genotyped. The heterozygote male and female were crossed to get homozygote, heterozygote, and wild-type fish. Functional kinetic coagulation assays and bleeding assays were performed on normal and mutant adult fish, and venous laser injury assays were performed on the larvae. The DNA from fviii and fv mutants were sequenced to confirm if they have a premature stop codon in exon 19, and in exon 2, respectively, and in both mutants, the amino acid glutamine is replaced with a stop codon. Homozygous and heterozygous 5 days post fertilization (dpf) larvae for fviii and fv deficient mutants exhibited prolonged time to occlusion after venous laser injury compared to wild-type controls. The homozygous and heterozygous fviii adult mutants showed modest bleeding and delayed fibrin formation in the kinetic partial thromboplastin time (kPTT) assay with their plasma. fv homozygous larvae had poor survival beyond 12 dpf. However, heterozygous fv mutants exhibited heavy bleeding and prolonged fibrin formation in the kPTT and kPT assay compared with wild-type siblings. Our characterization showed fviii and fv mutants from ZIRC phenocopied to a considerable extent classical hemophilia A and factor V deficiency in humans, respectively. These models should be useful in studying and developing novel drugs that reverse the phenotype and in generating suppressor mutations to identify novel factors that compensate for these deficiencies.

Utility of ACMG classification to support interpretation of molecular genetic test results in patients with factor VII deficiency

Background

The American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) have introduced an internationally shared framework for variant classification in genetic disorders. FVII deficiency is a rare inherited autosomal recessive bleeding disorder with sparse data concerning ACMG classification.

Methods

To develop an approach which may improve the utility of molecular genetic test results, 129 patients with FVII deficiency were retrospectively assigned to six subgroups for exploratory analysis: F7 gene wildtype (group 1), ACMG 1 (benign variant) or ACMG 2 (likely benign variant), only (group 2), ACMG 3 (variant of uncertain significance) ± ACMG 1-2 heterozygous or not classified variant (group 3), ACMG 4 (likely pathogenic variant), or ACMG 5 (pathogenic variant) single heterozygous ± ACMG 1-3 single heterozygous (group 4), ACMG 4-5 homozygous or ≥2 ACMG 4-5 heterozygous or ≥1 ACMG 4-5 heterozygous plus either ACMG 1 c.1238G>A modifying variant homozygous or ≥2 ACMG 1-3 (group 5), FVII deficiency and another bleeding disorder (group 6).

Results

Eleven of 31 patients (35.5%) in group 5 had abnormal ISTH-BS (n = 7) and/or history of substitution with recombinant factor VIIa (n = 5) versus 4 of 80 patients (5.0%, n = 1 abnormal ISTH-BS, n = 3 substitution) in groups 1 (n = 2/22), 2 (n = 1/29), 3 (n = 0/9), and 4 (n = 1/20). Four of 18 patients (22.2%) with FVII deficiency and another bleeding disorder (group 6) had an abnormal ISTH-BS (n = 2) and/or history of substitution with recombinant factor VIIa (n = 3).

Conclusion

Patients with a homozygous ACMG 4-5 variant or with specific combinations of heterozygous ACMG 4-5 ± ACMG 1-3 variants exhibited a high-risk bleeding phenotype in contrast to the remaining patients without another bleeding disorder. This result may serve as a basis to develop a genotype/phenotype prediction model in future studies.

Testing strategies used in the diagnosis of rare inherited bleeding disorders

INTRODUCTION

Rare Bleeding Disorders have a low population prevalence and may not be recognized by most clinicians. In addition, knowledge gaps of the indicated laboratory tests and their availability add to the potential for delayed diagnosis or misdiagnosis. The lack of widely available commercial, regulatory body approved esoteric tests limit them to reference laboratories, thus limiting easy access for patients.

AREAS COVERED

A literature search of Pubmed, Medline, Embase and review of international society guidelines was performed. Additional references from published articles were reviewed. A patient-centered approach to recognition and evaluation of RBD is discussed.

EXPERT OPINION

Recognition of RBD relies on obtaining a detailed patient personal and family hemostatic history. Inquiry into a history of involvement of other organ systems is important and if present should lead to suspicion of an inherited platelet disorder or a variant of Ehlers Danlos Syndrome. Multiple factors contribute to the complexity of development of efficient algorithms for diagnostic testing. Limitations in diagnostic sensitivity and specificity of screening tests, diagnostic tests, and esoteric tests further compound the complexity of establishing a diagnosis. Educational efforts focusing on clinician awareness of RBDs and available testing options are vital for optimal management of such patients.

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.

Congenital Combined Bleeding Disorders, a Comprehensive Study of a Large Number of Iranian Patients

Congenital combined bleeding disorders (CBDs) are extremely rare disorders which mainly occur in regions with a high rate of consanguineous marriage. These disorders can present with a variety of symptoms ranging from mucocutaneous bleeding to life-threatening episodes. This study aims to evaluate the prevalence and clinical course of Iranian patients with congenital CBDs. This study is conducted on 450 patients with CBDs who were referred to the Iranian Comprehensive Hemophilia Care Center (ICHCC) between 2010 and 2020. All these patients were diagnosed through evaluation of past medical history and coagulation laboratory investigation. Out of 450 patients, 33 were entered in this study. Having excluded cases with factor (F) V and FVIII deficiency, as well as those with hereditary combined Vitamin K dependent clotting factor deficiency (VKCFD), We found the most common CBDs to be FV-FVII deficiency (n: 6, 18.1%), together with FVII and FX deficiency (n: 6, 18.1%). The most common reason for referral of these patients to ICHCC was postoperative bleeding (14.3%). The mean of The International Society on Thrombosis and Hemostasis-Bleeding Assessment Tool (ISTH-BAT) and condensed MCMDM-1VWD bleeding assessment tool were 9.6 ± 4.79 and 9.1 ± 4.87, respectively (P < 0.005). In 10 females of reproductive age, the mean of Pictorial Bleeding Assessment Chart (PBAC) score was 649.3 ± 554. Among all patients, 23 (69.7%) received on-demand replacement therapy, whereas 5 patients (15.1%) received prophylaxis. In Iran, the coinheritance of bleeding disorders is surprisingly higher than expected. Moreover, patients with congenital CBDs may experience serious bleeding manifestations.

Maintaining plasma quality and safety in the state of ongoing epidemic - The role of pathogen reduction

In the field of transfusion medicine, many pathogen reduction techniques (PRTs) are currently available, including those based on photochemical (PI) and photodynamic inactivation (PDI). This is particularly important in the face of emerging viral pathogens that may pose a threat to blood recipients, as in the case of the COVID-19 pandemic. However, PRTs have some limitations, primarily related to their adverse effects on coagulation factors, which should be considered before their intended use. A comprehensive search of PubMed, Wiley Online Library and Science Direct databases was conducted to identify original papers. As a result, ten studies evaluating fresh plasma and frozen-thawed plasma treated with different PI/ PDI methods and evaluating concentrations of coagulation factors and natural anticoagulants both before and after photochemical treatment were included in the review. The use of PI and PDI is associated with a significant decrease in the activity of all analysed coagulation factors, while the recovery of natural anticoagulants remains at a satisfactory level, variable for individual inactivation methods. In addition, the published evidence reviewed above does not unequivocally favour the implementation of PI/PDI either before freezing or after thawing as plasma products obtained with these two approaches seem to satisfy the existing quality criteria. Based on current evidence, if implemented responsibly and in accordance with the current guidelines, both PI and PDI can ensure satisfactory plasma quality and improve its safety.

[Reduction of FXIII during myelosuppression in acute leukemia after chemotherapy and adverse relation with bleeding events]

Objective: To explore the relationship between plasma coagulation factor XIII (FXIII) and bleeding events. Methods: A total of 55 cases of acute leukemia (AL) at the myelosuppression phase after chemotherapy hospitalized in our hospital from August 2017 to March 2018 were enrolled, with 35 normal controls. The concentration of plasma coagulation factor XIII (FXIII) was detected by ELISA to determine the relationship between the plasma FXIII levels in AL patients at the myelosuppression phase after chemotherapy with bleeding events. Results: The level of FXIII in AL patients at the myelosuppression phase after chemotherapy was significantly lower than that in controls (P<0.001) . The level of FXIII was inversely related with the bleeding severity (the Spearman correlation coefficient -0.761) . Given the diagnosis cut-off point of FXIII concentration as 103.9 μg/L, the sensitivity of diagnosing bleeding in AL patients at the myelosuppression phase after chemotherapy was 0.939, and the specificity 0.909. Conclusion: AL patients at the myelosuppression phase after chemotherapy had low level of plasma FXIII, and patients with lower plasma FXIII associated with higher incidence and severity of bleeding. FXIII level was an independent influencing factor of bleeding in AL patients at the myelosuppression phase after chemotherapy.

The use of prophylaxis in the treatment of rare bleeding disorders

Rare bleeding disorders (RBDs) are a heterogeneous group of coagulation factor deficiencies that include fibrinogen, prothrombin, α₂-antiplasmin, plasminogen activator inhibitor-1, and factors II, V, V/VIII, VII, X, XI and XIII. The incidence varies based upon the disorder and typically ranges from 1 in 500,000 to 1 per million population. Symptoms vary with the disorder and residual level of the clotting factor, and can range from relatively minor such as epistaxis, to life threatening, such as intracranial hemorrhage. Rapid treatment of bleeding episodes in individuals with severe bleeding phenotypes is essential to preserve life or limb and to prevent long-term sequelae; therapeutic options depend on the deficiency and range from plasma-derived (eg, fresh frozen plasma, prothrombin complex concentrates, factor X concentrate) to highly purified and recombinant single factor concentrates. The rarity of these disorders limits the feasibility of conventional prospective clinical trials; instead, clinicians rely upon registries, published case reports/series and experience to guide treatment. In some disorders, long-term prophylactic therapy is administered in response to the bleeding phenotype in an individual patient or based on the known natural history and severity of the deficiency. Intermittent prophylaxis, surrounding surgery, pregnancy, labor, and menstruation may be required to prevent or control excessive bleeding. This review summarizes therapeutic options, guidelines, recommendations and observations from the published literature for long-term, surgical, gynecological, and obstetric prophylaxis in deficiencies of fibrinogen; prothrombin; factors II, V, V/VIII, VII, X, XI and XIII; combined vitamin-K dependent factors; α2-antiplasmin; and plasminogen activator inhibitor 1. Platelet disorders including Glanzmann's thrombasthenia and Bernard-Soulier syndrome are also addressed.

Factor VII Gene Defects: Review of Functional Studies and Their Clinical Implications

Coagulation factors belong to a family of plasma glycosylated proteins that should be activated for appropriate blood coagulation. Congenital deficiencies of these factors cause inheritable hemorrhagic diseases. Factor VII (FVII) deficiency is a rare bleeding disorder with variable clinical symptoms. Various mutations have been identified throughout the F7 gene and can affect all the protein domains. The results of previous experiments have partly revealed the correlation between genotype and phenotype in patients with FVII deficiency. Nevertheless, each particular variant may affect the coagulative function of FVII, mainly via altering its expression level, extra-cellular secretion, tissue factor binding affinity, or proteolytic activity. The pathogenicity of the variants and molecular mechanisms responsible for clinical symptoms in patients with FVII deficiency should be characterized via in silico and in vitro, as well as in vivo functional studies. This review has highlighted the most important functional studies reported on F7 gene variants, including relevant reports regarding Iranian FVII deficiency patients.