Clinical decision-making in thrombotic disorders is impeded by long-standing uncertainty regarding the magnitude of venous and arterial thrombosis risk associated with low protein S. Population-scale multiomic datasets offer an unprecedented opportunity to answer questions regarding the epidemiology and clinical impacts of protein S deficiency. To evaluate the risk associated with protein S deficiency across multiple thrombosis phenotypes. Cross-sectional study using longitudinal population cohorts derived from the UK Biobank (n = 426 436) and the US National Institutes of Health All of Us (n = 204 006) biorepositories. UK Biobank participants were enrolled in 2006-2010 (last follow-up, May 19, 2020) and underwent whole exome sequencing, with a subset (n = 44 431) having protein S levels measured by high-throughput plasma proteomics. Recruitment for All of Us began in 2017 and is ongoing, with participants receiving germline whole genome sequencing. Both cohorts include individual-level data on demographics, laboratory measurements, and clinical outcomes. Presence of rare germline genetic variants in PROS1, segmented by functional impact score (FIS), an in silico prediction of the probability that a genetic variant will disrupt protein activity. Firth logistic regression and linear regression modeling were used to evaluate the thrombosis risk associated with low plasma protein S levels and PROS1 variants across a range of FIS ratings. The UK Biobank cohort was 54.3% female, with a median age of 58.3 (IQR, 50.5-63.7) years at enrollment. Most participants (95.6%) were of European ancestry, and 18 011 had experienced a venous thromboembolism (VTE). In this population cohort, heterozygosity for the highest-risk PROS1 variants with an FIS of 1.0 (nonsense, frameshift, and essential splice site disruptions) was rare (adjusted prevalence, 0.0091% in the UK and 0.0178% in the US) and associated with markedly increased risk of VTE (odds ratio [OR], 14.01; 95% CI, 6.98-27.14; P = 9.09 × 10-11). Plasma proteomics (n = 44 431) demonstrated that carriers of these variants had total protein S levels that were 48.0% of normal (P = .02 compared with noncarriers). In contrast, less damaging missense variants (FIS ≥0.7) occurred more commonly (adjusted prevalence, 0.22% in the UK and 0.20% in the US) and were associated with marginally reduced plasma protein S concentrations and a smaller point estimate for VTE risk (OR, 1.977; 95% CI, 1.552-2.483; P = 1.95 × 10-7). Associations between PROS1 and VTE at both FIS cutoffs were independently validated in the All of Us cohort with similar effect sizes. No association was detected between the presence of coding PROS1 variants and 3 forms of arterial thrombosis: myocardial infarction, peripheral artery disease, and noncardioembolic ischemic stroke. The presence of PROS1 variants correlated poorly with low plasma protein S levels, and protein S deficiency was significantly associated with VTE and peripheral artery disease regardless of PROS1 variant carrier status. The elevated risk of VTE associated with germline loss of function in PROS1 was evident in Kaplan-Meier survival analysis and appeared to persist throughout life (log-rank P = .0005). True inherited loss of function in PROS1 is rare but represents a stronger risk factor for VTE in the general population than previously understood. Acquired, environmental, or trans-acting genetic factors are more likely to cause circulating protein S deficiency than coding variation in PROS1, and low plasma protein S is associated with VTE.

Long-term anticoagulation is recommended in patients with venous thromboembolism (VTE) deemed at high risk for recurrence (HRR). Limited information is available on patients with recurrent VTE and/or severe thrombophilia. In addition, these patients were not included in studies evaluating long-term treatment with low doses of direct oral anticoagulants (DOACs). The aims of our study were to (1) record the drugs and dosages used in HRR patients, and (2) to record adverse events occurring during follow-up. Among 2520 VTE patients enrolled in the Survey on anTicoagulated pAtients RegisTry 2, we retrospectively analyzed the management of patients with a history of recurrent VTE and/or severe thrombophilia (HRR patients). A total of 487 HRR patients were analyzed. Anticoagulants were stopped in 11 of 487 patients (2.3%), full-dose DOACs were continued in 176 patients (36.1%), and 311 patients (63.9%) were shifted to low-dose DOACs (61.4% with apixaban 2.5 mg twice a day and 38.6% with rivaroxaban 10 mg once a day) after a median time of 1.3 years (range, 0.5-20.2 years). During follow-up, no adverse events were recorded in patients who stopped treatment. Among patients who continued treatment, 10 had recurrent VTE (rate, 0.4 × 100 patient-years) and 19 had bleeding (rate, 0.9 × 100 patient-years). The risk of recurrent VTE was similar between patients on full-dose and low-dose anticoagulation. Patients on full-dose anticoagulation had a trend toward a higher bleeding risk (relative risk, 2.2; 95% CI, 0.7-9.0). HRR patients with a history of unprovoked recurrent VTE and/or patients with severe thrombophilia treated with long-term low-dose DOACs showed a low risk for recurrence and bleeding events.

Hereditary angioedema (HAE), caused by C1 inhibitor protein deficiency, was recently shown to be associated with an increased risk for venous thromboembolism (VTE). To our knowledge, this is the first national family study of HAE, which aimed to determine the familial risk of VTE. The Swedish Multi-Generation Register was linked to the Swedish National Patient Register for the period of 1964 to 2018. Only patients with HAE with a validated diagnosis were included in the study and were linked to their family members. Hazard ratios (HRs) and 95% confidence intervals (CIs) for VTE were calculated for patients with HAE in comparison with relatives without HAE. Among 2006 individuals (from 276 pedigrees of 365 patients with HAE), 103 individuals were affected by VTE. In total, 35 (9.6%) patients with HAE were affected by VTE, whereas 68 (4.1%) non-HAE relatives were affected (P < .001). The adjusted HR for VTE among patients with HAE was 2.51 (95% CI, 1.67-3.77). Patients with HAE were younger at the first VTE than their non-HAE relatives (mean age, 51 years vs 63 years; P < .001). Before the age of 70 years, the HR for VTE among patients with HAE was 3.62 (95% CI, 2.26-5.80). The HR for VTE for patients with HAE born after 1964 was 8.29 (95% CI, 2.90-23.71). The HR for VTE for patients with HAE who were born in 1964 or earlier was 1.82 (95% CI, 1.14-2.91). HAE is associated with VTE among young and middle-aged individuals in Swedish families with HAE. The effect size of the association is in the order of other thrombophilias. We suggest that HAE may be considered a new rare thrombophilia.

Pediatric Budd-Chiari syndrome (BCS) is a rare cause of portal hypertension and liver disease in Europe and North America. In order to understand the long-term effect of radiological intervention on BCS we performed a single center retrospective review. Fourteen cases were identified; 6 of 14 (43%) had a congenital thrombophilia with many having multiple prothrombotic mutations. Two were managed with medical anticoagulation alone and two required super-urgent transplant for acute liver failure. The remaining 10 of 14 (71%) underwent radiological intervention: 1 of 14 thrombolysis, 5 of 14 angioplasty, and 4 of 14 transjugular intrahepatic portosystemic shunt (TIPS). Six of 14 (43%) patients required repeat radiological intervention (1 angioplasty, 5 TIPS) but none required surgical shunts or liver transplantation for chronic liver disease. The time between diagnosis and treatment did not predict the need for repeat radiological intervention. These data show that radiological intervention can be highly effective, and reduces the need for surgery, though it requires specialist multidisciplinary teams for monitoring.

Recent non-malignant non-cirrhotic portal venous system thrombosis (PVT) is a rare condition. Among risk factors for PVT, cytomegalovirus (CMV) disease is usually listed based on a small number of reported cases. The aim of this study was to determine the characteristics and outcomes of PVT associated with CMV disease. We conducted a French multicenter retrospective study comparing patients with recent PVT and CMV disease ("CMV positive"; n = 23) to patients with recent PVT for whom CMV testing was negative ("CMV negative"; n = 53) or unavailable ("CMV unknown"; n = 297). Compared to patients from the "CMV negative" and "CMV unknown" groups, patients from the "CMV positive" group were younger, more frequently had fever, and had higher heart rate, lymphocyte count and serum ALT levels (p ≤0.01 for all). The prevalence of immunosuppression did not differ between the 3 groups (4%, 4% and 6%, respectively). Extension of PVT was similar between the 3 groups. Thirteen out of 23 "CMV positive" patients had another risk factor for thrombosis. Besides CMV disease, the number of risk factors for thrombosis was similar between the 3 groups. Heterozygosity for the prothrombin G20210A gene variant was more frequent in "CMV positive" patients (22%) than in the "CMV negative" (4%, p = 0.01) and "CMV unknown" (8%, p = 0.03) groups. Recanalization rate was not influenced by CMV status. In patients with recent PVT, features of mononucleosis syndrome should raise suspicion of CMV disease. CMV disease does not influence thrombosis extension nor recanalization. More than half of "CMV positive" patients have another risk factor for thrombosis, with a particular link to the prothrombin G20210A gene variant. Patients with cytomegalovirus (CMV)-associated portal venous system thrombosis have similar thrombosis extension and evolution as patients without CMV disease. However, patients with CMV-associated portal venous system thrombosis more frequently have the prothrombin G20210A gene variant, suggesting that these entities act synergistically to promote thrombosis.