Coagulation Factor XI (FXI) and Factor XII (FXII) deficiencies are rare. FXI deficiency is associated with a bleeding disorder, while FXII deficiency is not, but both can cause chronic prolongation of activated partial thromboplastin time and impair thrombus formation, posing great challenges for hemodialysis anticoagulation. Traditionally, heparin or low-molecular-weight heparins (LMWHs) are not considered a safe anticoagulation option for patients with increased bleeding risk. In this context, FXI and FXII have received substantial attention as targets for new anticoagulants. We present the case of a 68-year-old woman with combined FXI and FXII deficiencies who successfully underwent hemodialysis with anticoagulation using a low dose of LMWHs. This case highlights that FXI and FXII deficiencies are associated with anticoagulant effects, which can reduce the dosage of anticoagulant during hemodialysis. With careful monitoring, an appropriate dosage of LMWHs is still an acceptable option for patients with a bleeding risk.

BACKGROUND: Factor (F) XI deficiency is an inherited bleeding disorder with increased prevalence in Ashkenazi Jews where it is mainly caused by two variants, p.Glu135* (type II, leading to a null allele) and p.Phe301Leu (type III, missense variant). Inhibitor development is rare, and only seen in severe FXI deficiency (<20 IU/dL) upon exposure to plasma-based products. We report our experience of a large cohort of patients with severe FXI deficiency, including seven patients who developed FXI alloinhibitors, their presentation, natural history and subsequent perioperative management.
METHODS: A single-centre retrospective database review of patients with FXI deficiency, including those who have subsequently developed inhibitors, and extraction of clinical, laboratory and genotype data, including operative management records.
RESULTS: A total of 682 patients were identified with FXI deficiency, of whom 113 had FXI < 20 IU/dL and 42 had FXI ≤ 1 IU/dL. Factor XI inhibitors were seen in seven patients, six of whom were homozygous for the type II variant (prevalence of inhibitor with this genotype of 30%, risk of inhibitor upon plasma exposure 50%). FXI inhibitors were not seen, despite similar exposures, in patients with other genotypes. No alteration in bleeding phenotype occurred after inhibitor development and subsequent surgery was managed on 13 occasions with recombinant factor VIIa (rFVIIa), including low doses (15-30 µg/kg), with good haemostasis. The inhibitor spontaneously disappeared in four of seven patients over 1-22 years.
CONCLUSIONS: FXI inhibitors were only observed in severe FXI deficient patients homozygous for p.Glu135* (null allele) upon plasma or FXI concentrate exposure, with a 30% prevalence. The bleeding phenotype was not altered and inhibitors may disappear with time. Adequate haemostasis in the perioperative setting is achievable with low doses of rFVIIa.

Sheehan\'s syndrome (SS) is a condition characterized by panhypopituitarism that generally occurs after an episode of postpartum bleeding. There are certain hypotheses regarding the development of SS in the postpartum period. Coagulation factor abnormalities have been reported to be associated with SS. Associated hypothyroidism and hypocortisolism have been found to cause coagulation abnormalities. After the correction of the hypothyroidism and hypocortisolism, there is a gradual correction of the coagulation abnormality. In our case, a middle-aged woman presented with recurrent episodes of hospital admission because of generalized weakness and fever. She was found to have a biochemistry profile suggestive of hypopituitarism with preserved gonadal function. Her hemogram was normal, but the coagulogram showed a prolongation of activated partial thromboplastin time with a near-normal prothrombin time. She was evaluated and found to have factor XI deficiency. In the background of excessive vaginal bleeding and hypopituitarism, a diagnosis of SS was made. The presence of factor XI deficiency may have led to excessive bleeding and the development of SS. To the best of our knowledge, there is no reported association of factor XI deficiency with SS in the literature, and this is the first reported case.

BACKGROUND: The management of Factor XI deficiency is challenged by a variable association between FXI level and bleeding phenotype. Additionally, there is scarce data describing management strategies and their outcomes, specifically bleeding, thrombosis, and other complications.
OBJECTIVE: To evaluate bleeding, thrombosis, and other complications in individuals with severe FXI deficiency seen in our comprehensive haemophilia treatment centre (HTC). Peri-procedural management strategies and the resulting impact on bleeding and other clinically relevant outcomes were reported.
METHODS: Retrospective review of the electronic medical record of adult patients with severe FXI deficiency (< 20% activity) seen at a New York City comprehensive HTC between 2017 and 2022. Procedures, haemostatic management, and outcomes were collected and analysed.
RESULTS: We identified 38 individuals (64%) females with severe FXI deficiency. The mean age was 56 ± 21 years (SD). The median FXI activity level was 3% (IQR: 1-8%). The mean BAT score was 3.1 ± 2.4; (52%) individuals did not have a history of bleeding. A total of 256 surgeries and procedures were performed. There was reduced bleeding with preventative or reactive treatment during procedures. Arterial but not venous thrombotic complications were observed. Plasma was mostly used for procedures associated with higher risk of bleeding and antifibrinolytics for procedures at sites of high fibrinolysis.
CONCLUSIONS: Current management strategies pose a burden of care for these patients and manifested as nonbleeding adverse events and changes in clinical management. These findings highlight the need for novel investigation in predicting and managing bleeding for individuals with severe FXI deficiency.

Factor XI deficiency is a rare disorder with an unpredictable bleeding tendency. Here, we report the successful use of the sonic estimation of elasticity via resonance sonorheometry for guiding the management of haemostasis in a patient with a severe factor XI deficiency in repeated revision hip surgeries. Regardless of an administration of fresh frozen plasma, a significant haemorrhage occurred at the first of three hip surgeries. The repeat application of fresh frozen plasma normalised the prolonged activated partial thromboplastin time and the resonance sonorheometry clot time values; the factor XI activity increased to a sufficient level. No significant bleeding occurred in the second and third hip surgery. Using a resonance sonorheometry guided approach in haemostasis management has the potential to improve safety for patients with factor XI deficiency undergoing surgery by ensuring sufficient clotting and preventing side effects.

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.
CONCLUSIONS: 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.

Although two clusters have been identified in France, constitutional factor XI deficiency is a rare disorder. Acquired factor XI deficiency is extremely rare. The management of factor XI deficiency is not staightforward because of the unpredictable bleeding tendency that does not clearly relate to the factor XI level. Other haemostastis parameters have to be taken into account to evaluate the bleeding tendency. We report the cases of a congenital factor XI deficiency, an acquired factor XI deficiency and a von Willebrand disease associated to a factor XI deficiency. On the other hand, some interferences can lead to underestimation of factor XI and we report the case of an interference by lupus anticoagulant. The objective of this review is to better understand how to manage a reduced factor XI level.

Factor XI deficiency is a rare disorder of hemostasis. Previously also known as \"hemophilia C\", this defect has been regarded as a risk factor for bleeding. However, it has been known for long that bleeding tendency and severity of bleeding are not related to the residual factor XI activity in symptomatic patients. Moreover, a large proportion of patients with even severe factor XI deficiency are clinically unremarkable and do not show any signs of abnormal bleeding. Here, we present two cases of factor XI deficiency with a non-bleeding phenotype. Adequate diagnostic work-up and evaluation of the bleeding risk are reported and discussed with focus on thrombin generation assays (TGA) for the prediction of bleeding in affected patients. This is of high relevance in affected patients, particularly in the context of surgery.

BACKGROUND Bariatric surgery (BS) has a lower percentage of complications than other abdominal surgeries. Hemorrhage in one of the most common complications and can be life-threatening. Hereditary factor XI (FXI) deficiency is a coagulation disorder that can result in excessive bleeding requiring intervention to restore hemostasis. Risks over benefits in patients with morbid obesity with BS indication, as well as those with FXI deficiency, should be carefully evaluated. This article reports the case of an obese woman with FXI deficiency -undergoing SG. CASE REPORT A 49-year-old woman with a BMI of 51 kg/m² was diagnosed as having severe FXI deficiency during preoperative exams prior to bariatric surgery. Virus-inactivated homo-group plasma 10 ml/kg infusion was administrated 1 h before surgery, during the entire procedure, and continuing until postoperative day (POD) 4. A very low-calorie ketogenic diet (VLCKD) was proposed to the patient 4 weeks before surgery. Laparoscopic sleeve gastrectomy was performed with staple-line reinforcement by oversewing the seromuscular layer using continuous suture. Subcutaneous enoxaparin 4000 U.I. was administered from POD 1 until POD 25 to prevent any thromboembolic event. The patient was discharged on POD 5 in good clinical condition. CONCLUSIONS Risks of bleeding andor thromboembolic events before or after BS are increased in patient with FXI deficiency. Bariatric surgery in these patients is safe in experienced BS centers, and the risks associated with the obesity seem to exceed those of the coagulopathy and surgery. Careful preoperative counseling, extensive hematological checks, and meticulous surgery are essential to reduce BS risks. Sleeve gastrectomy oversewing the stapler line seems a reasonable choice.

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