Two SERPINC1 variants affecting N-glycosylation of Asn224 cause severe thrombophilia not detected by functional assays.

Antithrombin deficiency, the most severe congenital thrombophilia, might be underestimated, as some pathogenic variants are not detected by routine functional methods. We have identified 2 new SERPINC1 variants, p.Glu227Lys and p.Asn224His, in 4 unrelated thrombophilic patients with early and recurrent thrombosis that had normal antithrombin activity. In one case, the mutation was identified by whole genome sequencing, while in the 3 remaining cases, the mutation was identified by sequencing SERPINC1 based on a single functional positive finding supporting deficiency. The 2 variants shared a common functional defect, an impaired or null N-glycosylation of Asn224 according to a eukaryotic expression model. Carriers had normal anti-FXa or anti-FIIa activities but impaired anti-FVIIa activity and a detectable loss of inhibitory function when incubating the plasma for 1 hour at 41°C. Moreover, the ß glycoform of the variants, lacking 2 N-glycans, had reduced secretion, increased heparin affinity, no inhibitory activity, and a potential dominant-negative effect. These results explain the increased thrombin generation observed in carriers. Mutation experiments reflected the role that Lysine residues close to the N-glycosylation sequon have in impairing the efficacy of N-glycosylation. Our study shows new elements involved in the regulation of N-glycosylation, a key posttranslational modification that, according to our results, affects folding, secretion, and function, providing new evidence of the pathogenic consequence of an incorrect N-glycosylation of antithrombin. This study supports that antithrombin deficiency is underestimated and encourages the development of new functional and genetic tests to diagnose this severe thrombophilia.

Thrombotic risk and features of patients with inferior vena cava agenesis: a multicentre, retrospective, observational study.

BACKGROUND: Inferior vena cava agenesis (IVCA) is a rare anomaly predisposing affected people to lower-limb venous thrombosis with low frequency of pulmonary embolism. Antenatal thrombosis and inherited thrombophilia have been suggested as causes of IVCA. However, there is little evidence on the clinical course and management of this condition. We designed a patient registry to assess the thrombotic risk and features of IVCA. METHODS: In this this multicentre, retrospective, observational study, we included patients with IVCA diagnosed by routine imaging from 20 hospitals in Spain (n=18), Portugal (n=1), and Italy (n=1). Patients were identified from a systematic search in radiology databases using data extraction software (cohort A) and alternative searches in medical records for confirmed IVCA (cohort B; option allowed when systematic approaches were unapplicable). Primary outcomes were clinical and imaging features, thrombotic risk, phenotype of IVCA-associated thrombosis, anticoagulant treatment, and the results of thrombophilia testing. FINDINGS: We included patients with IVCA diagnosed by routine imaging studies done between Jan 1, 2010, and Dec 31, 2022. In the systematic search, 4 341 333 imaging exams were screened from the radiology databases of eight centres. 122 eligible patients were enrolled in cohort A. A further 95 patients were identified by screening medical records at 12 centres, of whom 88 were eligible and included in cohort B, making a combined cohort of 210 patients. 96 (46%) of 210 patients were female and 200 (95%) were European or Hispanic. 60 (29%) of 210 patients had hepatic IVC interruption, whereas 150 (71%) had extrahepatic IVCA. In cohort A, 65 (53%) of 122 patients had venous thrombosis, with an estimated annual risk of 1·15% (95% CI 0·89-1·46). Extrahepatic IVCA was associated with a greater risk of venous thrombosis than hepatic IVCA (56 [67%] of 84 patients vs nine [24%] of 38 patients, odds ratio 5·31, 95% CI 2·27-12·43; p<0·0001). Analysis of 126 patients with venous thrombosis pooled from cohorts A and B showed early-onset (median age 34·6 years, IQR 23·3-54·3) and recurrent events (50 [40%] of 126 patients). Patients with extrahepatic IVCA had greater proportions of lower-limb venous thrombosis (95 [87%] of 109 vs nine [53%] of 17, p=0·0010) and recurrence (48 [44%] of 109 vs two [12%] of 17, p=0·015), but lower rates of pulmonary embolism (10 [10%] of 99 vs four [33%] of 12, p=0·044) than did patients with hepatic IVCA. 77 (63%) of 122 patients with thrombosis underwent indefinite anticoagulation. 32 (29%) of 111 patients (29 [34%] of 86 with thrombosis) had coexisting thrombophilias. The recurrence risk was lower for patients receiving indefinite anticoagulation (adjusted odds ratio 0·24, 95% CI 0·08-0·61; p=0·010), and greater for thrombophilias (3·19, 1·09-9·32; p=0·034). INTERPRETATION: This evaluation of a large patient cohort demonstrates the high thrombotic burden of IVCA. We have identified two distinct forms of IVCA, hepatic and extrahepatic, suggesting different underlying mechanisms. Beyond clinical characterisation, we draw attention to this orphan disease and highlight the need for its study and improved care. FUNDING: Spanish Society of Thrombosis and Haemostasis, Instituto de Salud Carlos III, FEDER, Fundación Séneca.

Incidence and clinical profile of venous thromboembolism in hospitalized COVID-19 patients from Madrid region.

BACKGROUND: COVID-19 related in-hospital venous thromboembolism (VTE) incidence is high but data reported vary significantly. Some studies show that up to half of the events are diagnosed early after admission. OBJECTIVES: To study symptomatic VTE incidence in acute COVID-19 hospitalized patients and to describe timing of VTE diagnosis. METHODS: Multicenter cohort of 5966 patients hospitalized with acute COVID-19. Multicenter Registry of 844 hospitalized patients with acute COVID-19 and associated acute VTE. RESULTS: By the time of cohort data collection, 68 patients (1.14%) were still hospitalized, 19.8% had died, and 5.4% required ICU. During a median follow-up of 6 days (IQR, 4-12), 183 patients (3.07%; 95% CI, 2.64-3.55) presented a symptomatic VTE event. The cumulative incidences of VTE at 7, 14 and 21 days in wards [2.3% (95% CI, 1.9-2.7), 3.6% (95% CI, 3.0-4.3), and 4.3% (95% CI, 3.5-5.1)] were similar to the ones reported in ICU [2.2% (95% CI, 1.0-4.4), 2.9% (95% CI, 1.5-5.3), and 4.1% (95% CI, 2.2-6.8)], but at 30 and 60 days were higher in ICU [6.9% (95% CI, 4.2-10.5), and 12.8% (95% CI, 8.1-18.5)] than in wards. Eighty-eight VTE events (48%) were diagnosed early, within 48 h of admission. VTE was not associated with death (HR, 0.79; 95% CI, 0.55-1.12). CONCLUSIONS: Incidence of symptomatic VTE in our COVID-19 cohort is consistent with that of other real-life studies recently published. Early VTE events are, along with COVID-19, the reason for admission rather than an in-hospital complication.

Management of acquired hemophilia A: results from the Spanish registry.

The Spanish Acquired Hemophilia A (AHA) Registry is intended to update the status of AHA in Spain. One hundred and fifty-four patients were included and retrospectively followed for a median of 12 months. Patients were predominantly male (56.3%), with median age at diagnosis of 74 years. AHA was more frequently idiopathic (44.1%) and autoimmune disorder-associated (31.7%). Thirty-four percent of patients were on antithrombotic therapy at diagnosis. Hemostatic treatment was used in 70% of patients. Recombinant activated factor VII was more frequently infused (60.3% vs 20.6% activated prothrombin complex concentrate). Only 1 patient did not achieve control of hemorrhage. Complete remission (CR) was achieved by 84.2% of cases after immunosuppressive therapy. Steroids alone were less efficient than the other strategies (68.2% vs 87.2%, P = .049), whereas no differences existed among these (steroids/cyclophosphamide, 88.5%, vs steroids/calcineurin inhibitors, 81.2%, vs rituximab-based regimens, 87.5%). Female sex and high inhibitor levels influenced CR negatively. Thirty-six deaths (23.8%) were reported. Main causes of death were infection (15 patients, 9.9%) and hemorrhage (5 patients, 3.3%). All hemorrhage-related and half the infection-related deaths occurred within 2 months of diagnosis. Prior antithrombotic therapy was inversely associated with survival, irrespective of age. Median age of nonsurvivors was significantly higher (79 vs 73 years in survivors). Patients dying of infection were older than the other nonsurvivors (85 vs 78 years). In summary, fatal infection in the first months is common in our series. Antithrombotic therapy is associated with mortality. Particular care should be taken to avoid misdiagnosis.

Defects of splicing in antithrombin deficiency.

BACKGROUND: There is increasing evidence supporting the relevance of aberrant splicing in multiple disorders. In antithrombin deficiency only 22 intronic mutations affecting splicing sites (7% of SERPINC1 mutations) are considered as splicing mutations. METHODS: SERPINC1 was analyzed by Sanger sequencing and MLPA in 141 unrelated cases with antithrombin deficiency. Plasma antithrombin was studied by functional and western blot assays, purified by FPLC and characterized by proteomic analysis. In silico predictions on splicing was done with the Human Splicing Finder software. RESULTS: We detected 89 different SERPINC1 defects, 13 with potential effect on splicing. Ten cases presented 9 mutations disturbing splicing sites, 5 new. Three gross or small gene defects also disturbed a correct splicing. Interestingly, the first duplication of a single exon ever described (c.1154-13_1218+115dup), caused mild deficiency (75%). A deeper intronic mutation (c.1154-14G>A), identified in three unrelated patients with traces of disulphide dimers of antithrombin in plasma, created a cryptic splicing site that might generate a variant with 4 additional in frame residues according to in silico predictions. This aberrant splicing was confirmed by proteomic analysis of the dimer purified from plasma. CONCLUSIONS: A high proportion of cases with antithrombin deficiency (up to 13%) may be explained by an aberrant splicing. Up to 15% of mutations in SERPINC1: splicing site variations, gross gene defects and deep intronic mutations, may affect a correct splicing with three potential consequences type I, type II, and even moderate antithrombin deficiency.

Antithrombin Dublin (p.Val30Glu): a relatively common variant with moderate thrombosis risk of causing transient antithrombin deficiency.

The key haemostatic role of antithrombin and the risk of thrombosis associated with its deficiency support that the low incidence of antithrombin deficiency among patients with thrombosis might be explained by underestimation of this disorder. It was our aim to identify mutations in SERPINC1 causing transient antithrombin deficiency. SERPINC1 was sequenced in 214 cases with a positive test for antithrombin deficiency, including 67 with no deficiency in the sample delivered to our laboratory. The p.Val30Glu mutation (Antithrombin Dublin) was identified in five out of these 67 cases, as well as in three out of 127 cases with other SERPINC1 mutations. Genotyping in 1593 patients with venous thrombosis and 2592 controls from two populations, revealed a low prevalent polymorphism (0.3 %) that moderately increased the risk of venous thrombosis (OR: 2.9; 95 % CI: 1.07-8.09; p= 0.03) and identified one homozygous patient with an early thrombotic event. Carriers had normal anti-FXa activity, and plasma antithrombin was not sensitive to heat stress or proteolytic cleavage. Analysis of one sample with transient deficit revealed a type I deficiency, without aberrant or increased latent forms. The recombinant variant, which lacked the two amino-terminal residues, had reduced secretion from HEK-EBNA cells, formed hyperstable disulphide-linked polymers, and had negligible activity. In conclusion, p.Val30Glu by affecting the cleavage of antithrombin's signal peptide, results in a mature protein lacking the N-terminal dipeptide with no functional consequences in normal conditions, but that increases the sensitivity to be folded intracellularly into polymers, facilitating transient antithrombin deficiency and the subsequent risk of thrombosis.

Long-term follow-up of atrial fibrillation patients in the NASPEAF study. Prospective evaluation of different antiplatelet treatments.

INTRODUCTION AND OBJECTIVES: In the NASPEAF (National Study for Prevention of Embolism in Atrial Fibrillation) trial, combination therapy with an anticoagulant and an antiplatelet was more effective than anticoagulation alone in patients with atrial fibrillation. We report long-term follow-up in these patients, including prospective evaluation of different antiplatelet therapies. METHODS: This analysis included 574 atrial fibrillation patients. Standard anticoagulation (international normalized ratio [INR] 2.0-3.0) was used as control therapy to compare with anticoagulation (INR 1.9-2.5) plus either triflusal at 600 mg/day, triflusal at 300 mg/day or aspirin at 100 mg/day. The primary endpoint was ischemic or hemorrhagic stroke, a systemic or coronary ischemic event, or cardiovascular death. The mean follow-up was 4.92 years. RESULTS: Long-term follow-up confirmed that combination therapy with an anticoagulant plus triflusal at 600 mg/day gave significantly better results than anticoagulation alone (hazard ratio [HR]=0.33; 95% confidence interval [CI], 0.14-0.80; P=.014). There was a significantly higher incidence of ischemic events with triflusal at 300 mg/day (P=.031) and of severe bleeding events with aspirin at 100 mg/day (P=.008). The mean INR was similar in the three combination therapy groups. The incidence of severe nongastric bleeding during combination therapy with triflusal was very low (0.3% of patients/year). CONCLUSIONS: Long-term follow-up confirmed that combination antithrombotic therapy with triflusal at 600 mg/day gave significantly better results than anticoagulant monotherapy. The results obtained with combination therapy with triflusal at 300 mg/day and with aspirin at 100 mg/day should be considered provisional because the treatment groups were small and treatment was not randomly assigned.

Antithrombotic therapy in elderly patients with atrial fibrillation: effects and bleeding complications: a stratified analysis of the NASPEAF randomized trial.

AIMS: Atrial fibrillation patients with prior embolism have a high risk of vascular events in spite of anticoagulant therapy and elderly patients carry an additional risk. We analysed and compared vascular events-rate between older and younger than 75 years atrial fibrillation patients randomized to anticoagulant-alone or combined antiplatelet plus moderate-level anticoagulant therapy. METHODS AND RESULTS: A total of 967 patients stratified by age and the history of prior embolism were randomized to therapeutic doses of anticoagulant-alone or combined antithrombotic therapy. Primary events were fatal and non-fatal ischaemic or haemorrhagic stroke/transient ischaemic attack, systemic embolism and myocardial infarction, sudden death and death from bleeding. The elderly, compared with the younger patients, had higher event-rate [hazard ratio 2.31 (95% confidence interval 1.37-3.90), P < 0.003]. The elderly suffered higher severe bleeding event-rate during anticoagulant therapy. The combined, compared with the anticoagulant therapy, reduced the vascular events-rate in the elderly (P = 0.012) and caused less intracranial haemorrhages and less bleeding mortality, although more non-fatal gastric bleeding. CONCLUSION: The elderly with AF had a higher event-rate than the younger patients. A higher severe bleeding event-rate was also registered in elderly patients receiving anticoagulant therapy. Combined, compared with anticoagulant therapy, significantly reduced vascular events and bleeding mortality in elderly patients.