Clinical manifestations and mutation spectrum of 57 subjects with congenital factor XI deficiency in China

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.

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.

Molecular basis of rare congenital bleeding disorders

Rare bleeding disorders (RBDs), including factor (F) I, FII, FV, FVII, combined FV and FVIII (CF5F8), FXI, FXIII and vitamin-K dependent coagulation factors (VKCF) deficiencies, are a heterogeneous group of hemorrhagic disorder with a variable bleeding tendency. RBDs are due to mutation in underlying coagulation factors genes, except for CF5F8 and VKCF deficiencies. FVII deficiency is the most common RBD with >330 variants in the F7 gene, while only 63 variants have been identified in the F2 gene. Most detected variants in the affected genes are missense (>50% of all RBDs), while large deletions are the rarest, having been reported in FVII, FX, FXI and FXIII deficiencies. Most were located in the catalytic and activated domains of FXI, FX, FXIII and prothrombin deficiencies. Understanding the proper molecular basis of RBDs not only can help achieve a timely and cost-effective diagnosis, but also can help to phenotype properties of the disorders.

Case of concurrent factor VII and factor XI deficiencies manifesting as spontaneous lower extremity compartment syndrome

Factor VII and XI deficiencies are rare bleeding disorders typically associated with mild or provoked bleeding. This case report describes a patient with factor VII and XI deficiencies with an unprovoked episode of lower extremity hematoma causing compartment syndrome requiring multiple surgeries, extensive transfusion of blood products, and ultimately amputation.

Phenotype and genotype analysis of patients with severe factor XI deficiency in Shaanxi Province, China

Congenital coagulation factor XI (FXI) deficiency is a rare bleeding disorder with a heterogeneous haemorrhagic phenotype and various hotspot gene mutations associated with race and geography. Studies on FXI deficiency in Shaanxi Province, China, are scarce. In this study, seven patients with severe FXI deficiency and several family members were analysed. The International Society on Thrombosis and Hemostasis-Bleeding Assessment Tool (ISTH-BAT) was applied to assess bleeding symptoms. FXI activity was determined using a one-stage method, and the FXI antigen was measured by enzyme-linked immunosorbent assay. Targeted capture next-generation sequencing and Sanger sequencing were applied to detect FXI gene mutations. The bleeding phenotype varied, although none of the participants had a history of spontaneous bleeding. One maternal received replacement therapy during the perinatal period, one female patient presented with menorrhagia, one male patient experienced severe postoperative bleeding and others were asymptomatic. Family members with heterozygous mutations were all asymptomatic. The FXI activity of all the patients ranged from less than 1 to 3.1 IU/dl, and a synchronous decrease in the FXI antigen was observed. Two missense mutations (p. Gly350Glu and p. Cys482Trp), one nonsense mutation (p. Gln384∗) and one novel frameshift mutation (p. Ser225Phefs∗16) were detected. The bleeding manifestations and severity of severe FXI deficiency varied and were not related to its activity. Three reported mutations and one novel frameshift mutation were identified, thus extending the mutation spectrum of FXI deficiency.

[Congenital factor Ⅺ deficiency: a retrospective analysis of 80 cases]

目的

分析遗传性凝血因子Ⅺ（FⅪ）缺乏症的临床表现、实验室检查、治疗及转归。

方法

对2006年9月至2020年10月就诊于中国医学科学院血液病医院的80例遗传性FⅪ缺乏症患者进行回顾性分析。结果 80例患者中，男33例（41.3％），女47例（58.8％），中位年龄32（2～66）岁。28例（35.0％）存在出血事件，其中自发性出血11例（13.8％），皮肤磕碰后瘀斑或出血9例（11.3％），手术后出血9例（11.3％），女性患者月经过多11例（23.4％），阴道分娩后出血1例（2.1％）。实验室检查表现为活化部分凝血活酶时间（APTT）延长、凝血酶原时间（PT）正常、FⅪ活性（FⅪ∶C）减低。9例（11.3％）患者接受F11基因检测，共检测到11种突变。27例（33.8％）患者接受新鲜冰冻血浆（FFP）治疗，15例（18.8％）手术前预防性输注患者均未发生术中、术后出血。

结论

多数遗传性FⅪ缺乏症患者无出血症状或症状轻微，FⅪ∶C与出血严重程度之间缺乏相关性，FⅪ∶C与F11基因纯合或杂合突变类型具有较好的一致性。预防性输注FFP可有效降低手术出血风险。

Characterization of hereditary factor XI deficiency in Taiwanese patients: identification of three novel and two common mutations

Hereditary coagulation factor XI (FXI) deficiency is a rare bleeding disorder, but information on FXI deficiency in Taiwanese patients remains scarce. We evaluated clinical and genetic features of severe FXI deficiency patients in Taiwan. We collected clinical information and performed coagulation laboratory tests and genetic studies in ten unrelated Taiwanese families with severe FXI deficiency. FXI coagulation activity was assayed using a one-stage method. FXI antigen was determined using enzyme-linked immunosorbent assay. Underlying genetic mutations were evaluated using direct sequencing methods. Ten unrelated Taiwanese patients with hereditary FXI deficiency and variable bleeding tendencies were analyzed. Half of the patients were male. The most common bleeding manifestations were easy bruising (40%), bleeding after dental procedures (40%), and postoperative bleeding (33%). Two patients (20%) were asymptomatic. No correlation was found between bleeding manifestations and baseline FXI levels. Three novel mutations were identified: c.1322delT p.Lys442Cysfs*8, c.599G > C p.Cys200Ser, and IVS4 c.325 + 2del124. Two common mutations, c.1107C > T p.Tyr369* (40%) and c.841C > T p.Gln281* (30%), were also found. No correlation existed between bleeding and FXI activity, highlighting the difficulty in predicting FXI deficiency-related bleeding. Three novel FXI genetic mutations and two common mutations were identified, contributing to the known spectrum of FXI deficiency-related mutations.

Gene variants in four pedigrees with hereditary coagulation factor XI deficiency and one novel mutation identification

: Coagulation factor XI (FXI) deficiency is a bleeding disorder with unpredictable severity. Patients with this condition usually suffer bleeding manifestations after trauma or surgery and are poorly correlated with plasma FXI activity (FXI:C). In the current study, we examined and identified the phenotype and genotype in four unrelated probands and their 32 relatives with hereditary FXI deficiency. The probands with severely reduced FXI:C but bleeding symptoms were only found in two probands. Mutation analysis showed that all the probands were FXI homozygous mutation or compound heterozygous mutation. Five mutations were identified including three nonsense mutations c.841C>T (p.Gln263X), c.1107C>A (p.Tyr351X) and c.1033A>T (p.Lys327X), respectively, one frameshift mutation c.1325delT (p.Leu424CysfsX8), and one splicing mutation c.326-1G>A. c.1033A>T (p. Lys327X), a novel mutation which lead to a premature stop codon at amino acid position 327, it may have an influence on protein characteristics and cause the corresponding disease.

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

INTRODUCTION

Factor XI (FXI) deficiency is a rare disorder with molecular heterogeneity in Caucasians but relatively frequent and molecularly homogeneous in certain populations.

AIM

To characterize FXI deficiency in a Spanish town of 60 000 inhabitants.

METHODS

A total of 324 764 APTT tests were screened during 20 years. FXI was evaluated by FXI:C and by Western blot. Genetic analysis of F11 was performed by sequencing, multiplex ligation-dependent probe amplification and genotyping.

RESULTS

Our study identified 46 unrelated cases and 170 relatives with FXI deficiency carrying 12 different genetic defects. p.Cys56Arg, described as founder mutation in the French-Basque population, was identified in 109 subjects from 24 unrelated families. This mutation was also identified in 2% of the general population. p.Cys416Tyr, c.1693G>A and p.Pro538Leu were identified in 7, 6 and 2 unrelated families, respectively. NGS analysis of the whole F11 gene revealed a common haplotype for each of the four recurrent mutations, suggesting a founder effect. The analysis of plasma FXI of four p.Pro538Leu homozygous carriers revealed that this variant was not activated by FXIIa. We identified four mutations previously described in other Caucasian subjects with FXI deficiency (p.Lys536Asn; p.Thr322Ile, p.Arg268Cys and c.325G>A) and four new gene defects: p.(Cys599Tyr) potentially causing a functional deficiency, p.(Ile426Thr), p.(Ile592Thr) and the first worldwide duplication of 1653 bp involving exons 8 and 9. Bleeding was rare and mild.

CONCLUSIONS

Our population-cohort study supplies new evidences that FXI deficiency in Caucasians is more common than previously thought and confirmed the wide underlying genetic heterogeneity, caused by both recurrent and sporadic mutations.