Clinical and molecular epidemiology of factor XI deficiency in India

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.

Molecular heterogeneity of factor XI deficiency in Tunisia

Factor XI (FXI) deficiency is a rare inherited bleeding disorder that is highly prevalent in Ashkenazi Jewish ancestry but sporadically observed in most ethnic groups. It is heterogeneous both in clinical presentation and in genetic causality. Although a large spectrum of mutations associated with this disorder has been reported in several populations, genetic data of FXI deficiency in Tunisia are poorly described. The purpose of this study was to determine the molecular basis of FXI deficiency among Tunisian patients. Fourteen index cases from nine unrelated families with FXI deficiency, referred to Hemophilia Treatment Center of Aziza Othmana Hospital, were included in this study. The patients' F11 genes were amplified by PCR and subjected to direct DNA sequencing analysis. Sequencing analysis of F11 genes identified three distinct mutations; the Jewish type II nonsense mutation E117X, one previously reported missense mutation E602Q and one novel missense mutation V271M, which led to the disruption of the third apple domain structure of FXI. Furthermore, seven polymorphisms previously described, were also detected: C321F, c. 294A>G, -138 A>C, p.D125D, p.T249T, p.G379G, p.D551D. This report represents the first genetic study analyzing the molecular characteristics of factor XI deficiency within Tunisian population. Identification of the Jewish type II mutation in two families, as well as one missense previously reported mutation and one novel mutation confirmed the genetic heterogeneity of this disorder. Screening a large number of Tunisian factor XI deficient would reveal the spectrum mutations causing factor XI deficiency in Tunisia.

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.

Massive Hemoptysis Through Endotracheal Tube During Emergency Cesarean Delivery: A Case Report and Literature Review

Severe pulmonary hemorrhage occurred through the endotracheal tube during an emergency cesarean delivery. Intubation trauma was excluded with fiberoptic bronchoscopy. Episodes of hemoptysis continued for 48 hours. The patient was subsequently diagnosed with diffuse alveolar hemorrhage because of systemic lupus erythematosus. The diagnostic workup, successful management, and literature review are presented.

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.