High incidence of FXI deficiency in a Spanish town caused by 11 different mutations and the first duplication of F11: Results from the Yecla study

The spectrum of factor XI deficiency in Southeast China: four recurrent variants can explain most of the deficiencies

BACKGROUND

Factor XI (FXI) deficiency is an autosomal hemorrhagic disorder characterized by reduced plasma FXI levels. Multiple ancestral variants in the F11 gene have been identified in Ashkenazi Jews and other selected European populations. However, there are few reports of predominant variants in Chinese and/or East Asian populations. The aim of this study is to characterize the genotypes and phenotypes of FXI deficiency and identify the predominant variants.

RESULTS

Of the 41 FXI-deficient patients, 39 exhibited severe FXI defects, considerably more than those with partial defects. The APTT levels showed a negative correlation with FXI activity levels (coefficient=-0.584, P < .001). Only nine patients experienced mild bleeding, including one partially defective patient and eight severely defective patients. The majority of patients were referred for preoperative screenings (n = 22) and checkups (n = 14). Genetic analysis revealed that 90% of the patients had genetic defects, with 2, 16, and 19 cases of heterozygous, homozygous, and compound heterozygous patients, respectively. Seventeen variants were detected in the F11 gene (6 novel), including eleven missense variants, four nonsense variants, and two small deletions scattered throughout the F11. Of the 11 missense variants, six have not yet been studied for in vitro expression. Protein modeling analyses indicated that all of these variants disrupted local structural stability by altering side-chain orientation and hydrogen bonds. Nine variants, consisting of three missense and six null variants, were detected with a frequency of two or more. The highest allele frequency was observed in p.Q281* (21.25%), p.W246* (17.50%), p.Y369* (12.50%), and p.L442Cfs*8 (12.50%). The former two were variants specific to East Asia, while the remaining two were southeast China-specific variants.

CONCLUSION

Our population-based cohort demonstrated that no correlation between the level of FXI activity and the bleeding severity in FXI deficiency. Additionally, the prevalence of FXI deficiency may have been underestimated. The nonsense p.Q281* was the most common variant in southeast China, suggesting a possible founder effect.

Factor XI deficiency: phenotypic age-related considerations and clinical approach towards bleeding risk assessment

ABSTRACT

Factor XI (FXI) deficiency is a rare bleeding disorder that presents complex challenges in patient assessment and bleeding risk management. Despite generally causing mild to moderate bleeding symptoms, clinical manifestations can vary, and bleeding tendency does not always correlate with FXI plasma levels or genotype. Our manuscript delves into the age-related nuances of FXI deficiency across an individual's lifespan. We emphasize issues faced by specific groups, including neonates and females of reproductive age experiencing abnormal uterine bleeding and postpartum hemorrhage. Older patients present unique challenges and concerns related to the management of bleeding as well as thrombotic complications. The current assortment of diagnostic laboratory assays shows limited success in predicting bleeding risk in the perisurgical setting of patients with FXI deficiency. This review explores the intricate interplay between individual bleeding profiles, surgical sites, and FXI activity levels. We also evaluate the accuracy of existing laboratory assays in predicting bleeding and discuss the potential role of investigational global assays in perioperative assessment. Furthermore, we outline our suggested diagnostic approach to refine treatment strategies and decision making. Available treatment options are presented, including antifibrinolytics, replacement products, and recombinant activated FVII. Finally, we discuss promising nonreplacement therapies for the treatment of rare bleeding disorders that can potentially address the challenges faced when managing FXI deficiency-related bleeding complications.

Biology of factor XI

ABSTRACT

Unique among coagulation factors, the coagulation factor XI (FXI) arose through a duplication of the gene KLKB1, which encodes plasma prekallikrein. This evolutionary origin sets FXI apart structurally because it is a homodimer with 2 identical subunits composed of 4 apple and 1 catalytic domain. Each domain exhibits unique affinities for binding partners within the coagulation cascade, regulating the conversion of FXI to a serine protease as well as the selectivity of substrates cleaved by the active form of FXI. Beyond serving as the molecular nexus for the extrinsic and contact pathways to propagate thrombin generation by way of activating FIX, the function of FXI extends to contribute to barrier function, platelet activation, inflammation, and the immune response. Herein, we critically review the current understanding of the molecular biology of FXI, touching on some functional consequences at the cell, tissue, and organ level. We conclude each section by highlighting the DNA mutations within each domain that present as FXI deficiency. Together, a narrative review of the structure-function of the domains of FXI is imperative to understand the etiology of hemophilia C as well as to identify regions of FXI to safely inhibit the pathological function of activation or activity of FXI without compromising the physiologic role of FXI.

Rare bleeding disorders: Real-world data from a Spanish tertiary hospital

INTRODUCTION

Due to their low prevalence, rare bleeding disorders (RBDs) remain poorly characterized.

AIM

To gain insight of RBDs through our clinical practice.

METHODS

Retrospective study of the medical records of RBD patients followed up at the Central University Hospital of Asturias between January 2019 and December 2022.

RESULTS

A total of 149 patients were included. Factor (F) VII (44 %) and FXI (40 %) deficiencies were the most common diagnosed coagulopathies. Most of the patients were asymptomatic (60.4 %) and the most frequent type of bleeding were mucocutaneous and after surgery. All replacement treatments were administered on demand and no patient was on a prophylaxis regimen. Currently available products were safe; allergic reactions after administration of plasma were the most frequent complication. Genetic analysis, carried out on 55 patients (37 %), showed that the most frequent mutations in RBDs are of missense type (71.9 %). We identified 11 different novel genetic alterations in affected genes. The c.802C > T (p.Arg268Cys) variant, previously described, was identified in 71 % (15 of 21) of the patients with FXI deficiency genotyped and none were related (probable founder effect).

CONCLUSION

Our study on an unusual large single center cohort of RBD patients portrays location-dependent distinct genetic drives and clinical practice particularities.

One case of surgical treatment of coagulation factor XI deficiency complicated with esophageal cancer: a case report

BACKGROUND

Coagulation factor XI deficiency is an autosomal recessive hereditary disease with a low incidence. It usually occurs after surgery or trauma; Esophageal cancer is a common malignant tumor of the digestive tract in China. But so far, surgery-based comprehensive treatment of esophageal cancer still dominates.

CASE PRESENTATION

We report a case of an Asian patient with XI factor deficiency and lower esophageal squamous cell carcinoma who was admitted to our hospital recently. After active preoperative preparation, the operation was successfully performed, and there was no obvious abnormal bleeding during and after the operation.

CONCLUSIONS

Coagulation factor XI deficiency is a relatively rare disease, and patients with the disease will face a greater risk of bleeding during the perioperative period. The encouraging perioperative outcome enables us to have a deeper understanding of surgical treatment strategies for patients with Coagulation factor XI deficiency.

Hereditary coagulation factor XI deficiency: a rare or neglected disease? Results from a retrospective, single-centre cohort in northern Italy

To examine real-life clinical data regarding hereditary factor XI (FXI) deficiency from a secondary care centre. Retrospective review of clinical records for every FXI:C 0.7 IU/ml or less reported from 2012 to 2020. Seventy-nine patients were included. Six (7.6%) had a severe deficiency (FXI:C <0.2 IU/ml). Only 55 (69.6%) patients were referred to the Haemostasis Centre. Among them, six (15%) were subsequently not identified at increased haemorrhagic risk before a surgical/obstetrical procedure. Thirty-three (41.8%) experienced at least one bleeding event, minor (25 patients) and/or major (16 patients). Minor bleedings were predominantly spontaneous and more frequent in women, major events were mainly provoked. No correlation was found between FXI:C and risk of bleeding ( P  = 0.9153). Lower FXI:C, but not a positive bleeding history, was related with higher likelihood of being referred to the Haemostasis Centre ( P  = 0.0333). Hereditary FXI deficiency prevalence is likely underestimated, real-life clinical practices outside reference centres could be suboptimal.

Factor XI in Carriers of Antiphospholipid Antibodies: Elevated Levels Associated with Symptomatic Thrombotic Cases, While Low Levels Linked to Asymptomatic Cases

Antiphospholipid syndrome (APS) is a thromboinflammatory disorder caused by circulating antiphospholipid autoantibodies (aPL) and characterized by an increased risk of thrombotic events. The pathogenic mechanisms of these antibodies are complex and not fully understood, but disturbances in coagulation and fibrinolysis have been proposed to contribute to the thrombophilic state. This study aims to evaluate the role of an emerging hemostatic molecule, FXI, in the thrombotic risk of patients with aPL. Cross-sectional and observational study of 194 consecutive and unrelated cases with aPL recruited in a single center: 82 asymptomatic (AaPL) and 112 with primary antiphospholipid syndrome (APS). Clinical and epidemiological variables were collected. The profile of aPL was determined. Plasma FXI was evaluated by Western blotting and two coagulation assays (FXI:C). In cases with low FXI, molecular analysis of the F11 gene was performed. FXI:C levels were significantly higher in patients with APS than in patients with AaPL (122.8 ± 33.4 vs. 104.5 ± 27.5; p < 0.001). Multivariate analysis showed a significant association between symptomatic patients with aPL (APS) and high FXI (>150%) (OR = 11.57; 95% CI: 1.47-90.96; p = 0.020). In contrast, low FXI (<70%), mostly caused by inhibitors, was less frequent in the group of patients with APS compared to AaPL (OR = 0.17; 95%CI: 0.36-0.86; p = 0.032). This study suggests that FXI levels may play a causal role in the prothrombotic state induced by aPLs and holds the promise of complementary treatments in APS patients by targeting FXI.

Impact of genetic structural variants in factor XI deficiency: identification, accurate characterization, and inferred mechanism by long-read sequencing

BACKGROUND

Congenital factor XI (FXI) deficiency is a probably underestimated coagulopathy that confers antithrombotic protection. Characterization of genetic defects in F11 is mainly focused on the identification of single-nucleotide variants and small insertion/deletions because they represent up to 99% of the alterations accounting for factor deficiency, with only 3 gross gene defects of structural variants (SVs) having been described.

OBJECTIVES

To identify and characterize the SVs affecting F11.

METHODS

The study was performed in 93 unrelated subjects with FXI deficiency recruited in Spanish hospitals over a period of 25 years (1997-2022). F11 was analyzed by next-generation sequencing, multiplex ligand probe amplification, and long-read sequencing.

RESULTS

Our study identified 30 different genetic variants. Interestingly, we found 3 SVs, all heterozygous: a complex duplication affecting exons 8 and 9, a tandem duplication of exon 14, and a large deletion affecting the whole gene. Nucleotide resolution obtained by long-read sequencing revealed Alu repetitive elements involved in all breakpoints. The large deletion was probably generated de novo in the paternal allele during gametogenesis, and despite affecting 30 additional genes, no syndromic features were described.

CONCLUSION

SVs may account for a high proportion of F11 genetic defects implicated in the molecular pathology of congenital FXI deficiency. These SVs, likely caused by a nonallelic homologous recombination involving repetitive elements, are heterogeneous in both type and length and may be de novo. These data support the inclusion of methods to detect SVs in this disorder, with long-read-based methods being the most appropriate because they detect all SVs and achieve adequate nucleotide resolution.

Global epidemiology of factor XI deficiency: A targeted review of the literature and foundation reports

INTRODUCTION

Hereditary factor XI (FXI) deficiency is a rare coagulation disorder that may result in excessive bleeding requiring intervention to restore haemostasis.

AIM

The aim of this review was to report the current knowledge of the worldwide incidence and prevalence of FXI deficiency.

METHODS

A targeted PubMed search using terms related to FXI deficiency was conducted to identify studies published from April 2002 through April 2022. A manual search supplemented the electronic search. Studies were eligible for data abstraction if they reported population-based incidence proportions/rates or prevalence proportions for FXI deficiency.

RESULTS

The electronic and manual searches returned 253 publications. After applying exclusion criteria, seven publications were included in the analysis, including a global report from the World Federation of Haemophilia (WFH). Six publications provided information on the prevalence of FXI deficiency that included 74 countries and regions. The estimated prevalence of FXI in the WFH report ranged from 0/100,000 in several countries to 55.85/100,000 individuals in the United Kingdom. Prevalence estimates in the PubMed findings ranged from .1 to 246.2/1,000,000 inhabitants with varying methods of case identification and time periods of analysis. One study estimated the incidence of FXI deficiency in Yecla, Spain at 2% of blood donors and .09% of hospital inpatients/outpatients with activated partial thromboplastin time (aPTT) tests.

CONCLUSION

FXI deficiency is rare across the world, but additional steps could be taken to improve incidence and prevalence estimation, for example, development of a consistent FXI deficiency definition and incorporating genetic testing into a clinical routine to better identify and characterise cases.

Contact pathway in surgical and transcatheter aortic valve replacement

Background

Aortic valve replacement is the gold standard treatment for severe symptomatic aortic stenosis, but thrombosis of bioprosthetic valves (PVT) remains a concern.

Objective

To analyze the factors involved in the contact pathway during aortic valve replacement and to assess their impact on the development of thromboembolic complications.

Methods

The study was conducted in 232 consecutive patients who underwent: transcatheter aortic valve replacement (TAVR, N = 155), and surgical valve replacement (SAVR, N = 77) (MUVITAVI project). Demographic and clinical data, outcomes including a combined end point (CEP) of thrombotic events, and imaging controls were recruited. Samples were collected 24 h before and 48 h after valve replacement. FXII, FXI and (pre)kallikrein were evaluated by Western Blot and specific ELISA with nanobodies.

Results

The CEP of thrombotic events was reached by 19 patients: 13 patients presented systemic embolic events and 6 patients subclinical PVT. Valve replacement did not cause FXII activation or generation of kallikrein. There was a significant reduction of FXI levels associated with the procedure, which was statistically more pronounced in SAVR than in TAVR. Cases with reductions of FXI below 80% of basal values had a lower incidence of embolic events during the procedure than patients in whom FXI increased above 150%: 2.7 vs. 16.7%; p: 0.04.

Conclusion

TAVR or SAVR did not significantly activate the contact pathway. A significant reduction of FXI, was observed, particularly in SAVR, associated with lower incidence of thrombotic events. These results encourage evaluating the usefulness and safety of FXI-directed antithrombotic treatments in these patients.

Anticoagulant therapy in patients with congenital FXI deficiency

Bleeding risk of FXI deficiency on anticoagulation is unknown. We report 15 of 269 FXI-deficient subjects receiving VKA and/or DOACs.

No major bleeding was observed for >1000 months of anticoagulation. Drug dose, monitoring and management were unaffected by FXI deficiency.

The bleeding phenotype of factor XI (FXI) deficiency is unpredictable. Bleeding is usually mild and mostly occurs after injury. Although FXI deficiency renders antithrombotic protection, some patients might eventually develop thrombosis or atrial fibrillation, requiring anticoagulant therapy. There is almost no evidence on the bleeding risk in this scenario. Our retrospective study of 269 white FXI-deficient subjects (1995-2021) identified 15 cases requiring anticoagulation. They harbored 8 different F11 variants, mainly in heterozygosis (1 case was homozygote), and had mild to moderate deficiency (FXI:C: 20% to 70%). Two subjects (13.3%) had bleeding history before anticoagulation. Atrial fibrillation was the main indication (12/15; 80%). Fourteen patients started therapy with vitamin K antagonists (VKA), but 4 subjects were on direct oral anticoagulants (DOACs) at the end of follow-up. Over >1000 months of anticoagulation, 2 mild bleeding episodes in 2 patients (13.3%, 95% confidence interval: 3.7% to 37.9%) were recorded. No major/fatal events were reported. “Pre-post” bleeding localization and severity did not change despite treatment. On VKA, drug dosing and management were also standard, unaltered by FXI deficiency. We provide the largest description of anticoagulant use in FXI deficiency, and the first cases receiving DOACs. Although further studies are needed, our observations suggest that moderate FXI deficiency does not interfere with anticoagulant management nor bleeding risk.

Genomic Sequencing for Newborn Screening: Results of the NC NEXUS Project

Newborn screening (NBS) was established as a public health program in the 1960s and is crucial for facilitating detection of certain medical conditions in which early intervention can prevent serious, life-threatening health problems. Genomic sequencing can potentially expand the screening for rare hereditary disorders, but many questions surround its possible use for this purpose. We examined the use of exome sequencing (ES) for NBS in the North Carolina Newborn Exome Sequencing for Universal Screening (NC NEXUS) project, comparing the yield from ES used in a screening versus a diagnostic context. We enrolled healthy newborns and children with metabolic diseases or hearing loss (106 participants total). ES confirmed the participant's underlying diagnosis in 15 out of 17 (88%) children with metabolic disorders and in 5 out of 28 (∼18%) children with hearing loss. We discovered actionable findings in four participants that would not have been detected by standard NBS. A subset of parents was eligible to receive additional information for their child about childhood-onset conditions with low or no clinical actionability, clinically actionable adult-onset conditions, and carrier status for autosomal-recessive conditions. We found pathogenic variants associated with hereditary breast and/or ovarian cancer in two children, a likely pathogenic variant in the gene associated with Lowe syndrome in one child, and an average of 1.8 reportable variants per child for carrier results. These results highlight the benefits and limitations of using genomic sequencing for NBS and the challenges of using such technology in future precision medicine approaches.

Gynaecological and obstetrical bleeding in Caucasian women with congenital factor XI deficiency: Results from a twenty-year, retrospective, observational study

INTRODUCTION

Factor XI (FXI) deficiency is a mild bleeding disorder, common among Ashkenazis, that may be underestimated in Caucasians. Management of FXI deficiency in women is a challenge, due to its unpredictable bleeding tendency and the little evidence available on this issue.

OBJECTIVE

To describe gynaecological/obstetrical bleeding complications and to analyze the effectiveness and safety of the antihaemorrhagic treatment among women with FXI deficiency.

MATERIAL AND METHODS

A retrospective, observational study of 214 Caucasian subjects with FXI deficiency collected during 20 years (1994-2014) without clinical selection.

RESULTS

We identified 95 women with FXI deficiency. Any haemorrhagic event was communicated by 26/95 (27.4%), being abnormal uterine bleeding the most frequently found (12/95, 12.6%). Nine postpartum haemorrhages were recorded from 136 deliveries (6.6%) in 57 women. Four postsurgical bleeding complications were registered among 25 gynaecological surgeries (16%) in 20 women. Abnormal uterine bleeding, postpartum and postsurgical haemorrhages were related to both a positive bleeding history and FXI:C values ≤43.5%. Prophylaxis with fresh frozen plasma, used in 12/25 (48%) gynaecological surgeries, did not prevent from postoperative bleeding in three cases, but two developed severe adverse reactions.

CONCLUSION

Women with FXI deficiency, especially those with a positive history of bleeding or FXI:C ≤43.5%, are at risk of developing gynaecological/obstetrical haemorrhages, most of them mild/moderate. Systematic prophylaxis has questionable effectiveness, but might cause severe side effects.

Normal aPTT in children with mild factor XI deficiency

It has been suggested that persons with factor XI deficiency can have a normal activated partial thromboplastin time (aPTT). This notion is based on limited data, especially in children. Because of the central role the aPTT plays in diagnostic algorithms for bleeding disorders, it is important to know if a normal aPTT eliminates the need for factor XI activity testing. Our institutional database contains seven children with factor XI deficiency, of whom four have a normal aPTT. This supports the hypothesis that children with factor XI deficiency can have a normal aPTT. Clinicians may wish to consider this evidence when evaluating children with abnormal bleeding.