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Introduction Prothrombin Belgrade mutation is the result of the c.1787G>A substitution in the prothrombin gene. It is located in the antithrombin and sodium binding site and leads to impaired inactivation of thrombin by antithrombin, resulting in antithrombin resistance and thrombotic disorders. However, it negatively affects sodium binding and may have hypocoagulant effects. Considering that prothrombin Belgrade mutation mechanism is still not fully elucidated and that sodium binding is important for thrombin affinity towards fibrinogen, our aim was to determine whether this mutation affects fibrin clot formation and lysis. Methods Using HEK293T cell line, recombinant wild type and mutated prothrombin were generated by transient transfection. Samples that correspond to plasma of a non-carrier, heterozygous and homozygous carriers were reconstituted using prothrombin deficient plasma and recombinant proteins. Reconstituted samples were used in OHP assay (Overall Hemostasis Potential) to determine kinetic profiles of coagulation and fibrinolysis. Clot turbidity assay was performed to observe kinetics of clot formation and lysis more closely. Fibrin clots formed in reconstituted plasma samples were analyzed by confocal microscopy to determine density of fibrin network. Fibrin clots were additionally observed using electron microscopy to determine thickness of individual fibrin fibers. Results No significant difference found in OHP, OCP, OFP, and fibrin network density between wild type, heterozygous, and homozygous carrier reconstituted plasma samples. There were significant differences between samples for slope and slope time parameters in kinetic profiles and fibrin fiber thickness. Conclusions Results indicate that prothrombin Belgrade mutation has no significant impact on fibrinolysis, however it may affect kinetics of clot formation and its architecture.

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers worldwide. Lack of specific CRC symptoms is a challenge for clinicians, as the symptoms overlap with other non-cancerous diseases, leading to 20-25% of newly diagnosed CRC patients already having liver metastasis. Thus, discovering reliable early-disease biomarkers is of high importance. Non-coding RNAs (ncRNAs) have been demonstrated to be involved in CRC development and progression. Long non-coding RNAs (lncRNAs) can interact with RNA, DNA and proteins, forming complexes that are involved in regulation of gene expression via multiple mechanisms, affecting every stage of colon carcinogenesis and making them top candidates for novel biomarker discovery. The aim of our study was to conduct data mining of Gene Expression Omnibus (GEO) database by using “colon cancer” and “ncRNA” keywords, and identify differentially expressed lnRNAs present in different GEO datasets. GEO database which collects submitted high-throughput gene expression data was queried for all datasets that studied colon cancer and ncRNA. Over 60 datasets were manually inspected in order to identify those where analysis of colon and normal tissue originating from the same patient was done. Each dataset was analyzed by GEO2R software to discover differentially expressed lncRNAs. LncRNAs were considered significant if they appeared in more than one GEO dataset. Parts of lncRNAs sequences available in GEO2R analysis results were run through BLAST in order to identify full length lncRNAs. Five GEO datasets matched our criteria. We discovered 12 sequences that appeared in more than one dataset and we identified them through BLAST analysis. Six sequences originated from lncRNAs (RYR3 divergent transcript, long intergenic non-protein coding RNA 595, TOX divergent transcript, FLVCR2 antisense RNA 1, LHRI_LNC744.1 lncRNA gene, and ELFN1 antisense RNA 1), while six sequences represented partial sequences of various mRNAs. Four lncRNAs were do

Objective. To assess thrombin generation, fibrin formation, and structure together with the fibrinolytic status in patients with systemic sclerosis (SSc) in relation to the occurrence of digital ulcers (DUs) during the course of disease. Methods. We studied variables of endothelial dysfunction, thrombin generation, overall hemostatic potential, and fibrin clot turbidity in plasma from 58 patients with SSc (39 with DU history and 19 DU-naive) and 46 matched healthy controls (HCs). Fibrin structure was visualized using scanning electron microscopy (SEM). Finally, 39 patients with a history of DUs were followed for 1.5 years and the predictive value of all investigated markers for new DU onset was explored. Results. Significantly enhanced endogenous thrombin potential (ETP) and prolonged clot lysis time (CLT) were found in patients with DUs compared to HCs. CLT was prolonged in patients with DUs compared to those without, showing good validity in identifying DUs with an area under the curve of 0.7 (95% CI 0.6-0.8). The levels of ETP and intercellular adhesion molecule 1 were independently associated with CLT. Over the follow-up period, 20 patients developed new DUs. CLT was prolonged (P lt 0.001) in patients with new DU episodes, especially those with recurrent DUs. Regression analysis showed that the Raynaud phenomenon visual analog scale and CLT were predictors of new DUs (OR 1.1, 95% CI 1.0-1.1 and OR 1.2, 95% CI 1.1-1.3, respectively). SEM confirmed denser fibrin clots in patients with new DUs. Conclusion. Our results suggest that impaired fibrinolysis might have an emerging role in underlying digital vasculopathy and its progression in SSc.

Introduction. Ischemic stroke (IS) is a heterogeneous dis-order caused by several genetic and environmental risk factors. It was suggested that coagulation disorders cause 1-4% of cases with IS, especially in patients with early onset of IS. Case report. We describe a case of a young adult male who developed an unprovoked IS. Biochemical, immunological, and thrombophilia screening, as well as DNA sequencing, were performed in order to reveal molecular pathology underlying the stroke of the patient. Thrombophilia testing showed that patient was a homozygous carrier for PAI-1 4G/5G and MTHFR C677T mutations. Additional genetic analysis revealed the presence of the recently reported F2 c.1824C>T gene variant, located in the last exon of the pro-thrombin gene and has previously been shown to cause hy-perprothrombinemia, hypofibrinolysis, and altered fibrin clot phenotype. Conclusion. Our results suggest that the newly reported F2 c.1824C>T gene variant might have a synergistic effect with PAI 4G/4G and MTHFR 677TT genotype in the formation of altered fibrin clot phenotype characterized by thin, densely packed fibrin fibers, which makes clot less susceptible to fibrinolysis and greatly in-creases the risk for early ischemic stroke onset., Ishemijski moždani udar (IMU) je heterogeni poremećaj koji može biti uzrokovan genetskim faktorima rizika i faktorima sredine. Poremećaji koagulacije mogu biti uzročnici u 1-4% slučajeva IMU, naročito kod bolesnika kod kojih se IMU dogodi u mlađem životnom dobu. Prikaz bolesnika. Prikazan je slučaj bolesnika koji je u mlađem životnom dobu razvio IMU nepoznatog uzroka. Urađeni su biohemijski, imunološki i testovi za trombofiliju kao i sekvenciranje DNK sa ciljem da se utvrdi molekularna patologija koja je mogla biti u osnovi moždanog udara kod tog bolesnika. Testovima za trombofiliju utvrđeno je da je bolesnik homozigotni nosilac mutacija PAI-1 4G/5G i MTHFR C677T. Dodatnom genetičkom analizom otkriveno je prisustvo nedavno opisane F2 c.1824C>T genske varijante, koja se nalazi u poslednjem egzonu gena za protrombin i za koju je prethodno pokazano da izaziva hiperprotrombinemiju, hipofibrinolizu i izmenjeni fenotip fibrinskog ugruška. Zaključak. Naši rezultati ukazuju na to da bi nova F2 c.1824C>T genska varijanta mogla imati sinergistički efekat sa PAI 4G/4G i MTHFR 677TT genotipom u nastanku fibrinskog ugruška sa izmenjenim fenotipom, koji se odlikuje tankim, gusto upakovanim fibrinskim vlaknima, što čini ugrušak manje podložnim fibrinolizi i povećava rizik od nastanka IMU u ranijem životnom dobu.

J Rheumatol 2022; doi: 10.3899/jrheum.210931 In the Methods section, under the subheading “Follow-up and study outcome,” the last sentence should be as follows: “All new DUs were recorded by contacting all 39 patients once every 1–3 months during follow-up.” The error does not affect the results or conclusions of the study. This correction only applies to the April 1 First Release. The correct text appears in the print and online issues.

This study sought to identify different subpopulations of extracellular vesicles (EVs) in plasma from female patients with established rheumatoid arthritis (RA) in relation to the activation of coagulation and fibrin formation in these patients. Forty women were included in the study, 20 patients and 20 age-matched healthy controls. The mean disease duration in patients was 13.0 (5.0-25.0) years, with medium to high disease activity despite ongoing treatment with low-dose prednisolone and methotrexate. There were no differences between the investigated groups regarding the presence of traditional cardiovascular risk factors. The concentration of phosphatidylserine-positive (PS+) EVs; platelet (CD42a(+)), leucocyte (CD45(+)), monocyte (CD14(+)), and endothelial (CD144(+))-derived EVs; and EVs-expressing tissue factor (CD142(+)), P-selectin (CD62P(+)), and E-selectin (CD62E(+)) were determined by flow cytometry analysis. Overall hemostasis potential (OHP) was assessed to follow the hemostatic disturbances, including the parameters for overall coagulation potential (OCP) and overall fibrinolytic potential (OFP). Fibrin clot turbidity was measured together with clot lysis time, and scanning electron microscopy was performed. Increased concentrations of PS+, CD42a(+), CD142(+), CD45(+), CD14(+), and CD62P(+) EVs were found in plasma from patients with RA compared to healthy controls, and the concentrations of PS+, CD42a(+), CD14(+), and CD62P(+) EVs were positively correlated with the inflammatory parameters in RA patients. Positive correlations were also found between the levels of PS+ and CD42a(+) EVs and OCP as well as between the levels of PS+, CD42a(+), and CD62P(+)EVs and OHP. The levels of PS+, CD42a(+), CD14(+), CD62P(+), and CD62E(+) EVs were negatively correlated with OFP. Elevated levels of circulating EVs of different cell origins were found in patients with established RA, in relation to the inflammatory burden and coagulation activation in the disease.

Introduction For acute venous thromboembolism (VTE), a biomarker with higher specificity than D-dimer would be of great clinical use. Thrombin generation and overall hemostatic potential (OHP) reflect the hemostatic balance by globally assessing multiple coagulation factors and inhibitors. These tests discriminate between healthy controls and patients with a prothrombotic tendency but have yet to be established as clinical biomarkers of VTE. Objective This study compares endogenous thrombin potential (ETP) and OHP to D-dimer and fibrin monomers (FM) in outpatients with suspected VTE. Methods A cross-sectional diagnostic study where 954 patients with suspected pulmonary embolism or deep venous thrombosis were recruited consecutively from the medical emergency department at Karolinska University Hospital. D-dimer, FM, OHP, and ETP were analyzed in a subpopulation of 60 patients with VTE and 98 matched controls without VTE. VTE was verified either by ultrasonography or computed tomography and clinical data were collected from medical records. Results Compared with healthy controls, both VTE and non-VTE patients displayed prothrombotic profiles in OHP and ETP. D-dimer, FM, ETP area under the curve (AUC), and ETP T lag were significantly different between patients with VTE and non-VTE. The largest receiver-operating characteristic AUCs for discrimination between VTE and non-VTE, were found in D-dimer with 0.94, FM 0.77, and ETP AUC 0.65. No useful cutoff could be identified for the ETP or the OHP assay. Conclusion Compared with D-dimer, neither ETP nor OHP were clinically viable biomarkers of acute venous thrombosis. The data indicated that a large portion of the emergency patients with suspected VTE were in a prothrombotic state., Funding agencies: Foundation for Coagulation Research at Karolinska Institutet, the ScandinavianResearch Foundation for Varicose Veins and other Venous Diseases, FoU Region Stockholm, the Swedish Society onThrombosis and Haemostasis with Leo Pharma.

Introduction: Haemostatic balance shifted towards hypercoagulability in normal pregnancy is even more pronounced in pre-eclampsia (P-EC). The aim of this study was to analyse haemostatic disturbances and fibrin clot properties in women with pre-eclampsia and to investigate their association with maternal and foetal outcomes. Methods: Forty-six pregnant women diagnosed with pre-eclampsia were included in the study, with blood sampling done on the morning following admission to hospital, as well as after delivery (mean duration 4.8 days). Two global haemostatic assays—endogenous thrombin potential (ETP) and assay of overall haemostatic potential (OHP)—were employed, including fibrin clot turbidity measurements and scanning electron microscopy (SEM) of representative samples. Results: Three thrombin generation parameters (ETP, t_lag and peak height) and OHP were significantly increased in pre-eclampsia compared with controls, whereas overall fibrinolytic potential (OFP—determined as a parameter of the OHP assay) had significantly lower values. Clot lysis time was significantly prolonged in patients with pre-eclampsia. In the pre-eclamptic group after delivery, we observed a significant elevation in the peak height and a reduction in the time to peak and OFP compared with values before delivery. Pre-eclamptic patients with renal complications had significantly higher values for ETP, peak height and D-dimer. Turbidity measurements and SEM revealed dense fibrin structure in patients with pre-eclampsia. Conclusion: Patients with pre-eclampsia have enhanced coagulation and impaired fibrinolysis before, and even after, delivery. In particular, the presence of multi-organ dysfunction, such as renal dysfunction, may be associated with increased thrombin generation in pre-eclampsia.

BACKGROUND: Thrombosis is a major global disease burden with almost 60% of cases related to underlying heredity and most cases still idiopathic. Synonymous single nucleotide polymorphisms (sSNPs) are considered silent and phenotypically neutral. Our previous study revealed a novel synonymous FII c.1824C gt T variant as a potential risk factor for pregnancy loss, but it has not yet been associated with thrombotic diseases. METHODS: To determine the frequency of the FII c.1824C gt T variant we have sequenced patients' DNA. Prothrombin RNA expression was measured by quantitative PCR. Functional analyses included routine hemostasis tests, western blotting and ELISA to determine prothrombin levels in plasma, and global hemostasis assays for thrombin and fibrin generation in carriers of the FII c.1824C gt T variant. Scanning electron mi- croscopy was used to examine the structure of fibrin clots. RESULTS: Frequency of the FII c.1824C gt T variant was significantly increased in patients with venous thromboembolism and cerebrovascular insult. Examination in vitro demonstrated increased expression of prothrombin mRNA in FII c.1824C gt T transfected cells. Our ex vivo study of FII c.1824C gt T carriers showed that the presence of this variant was associated with hyperprothrom-binemia, hypofibrinolysis, and formation of densely packed fibrin clots resistant to fibrinolysis. CONCLUSION: Our data indicate that FII c.1824C gt T, although a synonymous variant, leads to the development of a prothrombotic phenotype and could represent a new prothrombotic risk factor. As a silent variant, FII c.1824C gt T would probably be overlooked during genetic screening, and our results show that it could not be detected in routine laboratory tests.

PURPOSE: Thrombosis is multicausal disease in which both acquired and genetic risk factors play important roles. The most frequent genetic risk factors known to date are the Factor V G1691A (FV Leiden) and FII G20210A mutations. On the other hand, inherited antithrombin (AT) deficiency, caused by mutations in the AT gene (SERPINC1) is a very rare disorder, but it is associated with significant risk for thrombotic complications. AT deficiency is classified into two types: type-I is a quantitative disorder characterized by decreased amount and activity of AT, while type-II is a qualitative - functional disorder. Aim of our study was to analyze the frequency of FV Leiden and FII G20210A mutations in patients with inherited AT deficiency from Serbia. METHODOLOGY: A study was carried out in large group of AT deficiency patients from Serbia. Cohort of 42 subjects (15m/27f; 36.7±18.7y) from 18 Serbian families included 24 symptomatic and 18 asymptomatic first-degree relatives. Among them, type-I AT deficiency were detected in 9 families (19 members: 6m/13f; 37.1±19.0y) and type-II in 9 families (23 members: 9m/14f; 36.5±18.8y). FV Leiden and FII G2010A mutations were detected by PCR, followed by digestion with specific restriction enzymes (PCR-RFLP). RESULTS: We have detected 3 FV Leiden heterozygous carriers in 3 different families (1 with type-I and 2 with type-II AT deficiency). All 3 carriers were symptomatic. Regarding FII G20210A mutation, 2 heterozygous carriers, both asymptomatic and from same family with type-I deficiency, were identified. According to our findings in families with AT deficiency from Serbia frequency of FV Leiden and FII G20210A mutation are 16.7% and 5.6%, respectively. CONCLUSION: This is the first study in which frequency of FV Leiden and FII G20210A mutations in patients with inherited AT deficiency from Serbia were examined. Results of our study suggest that these mutations can be relevant for AT deficiency patients’ phenotype, but further st

The link between thrombotic disorders and cancer has been known for over 150 years, although the precise mechanism of this relationship has not yet been resolved. Current data show that thrombin has a significant role in cancer metabolism, invasiveness, adhesion and survival. However, data regarding the expression of the thrombin precursor prothrombin in various cancer cell lines are scarce. Therefore, it was our objective to determine whether common cancer-derived cell lines (Caco-2, MCF-7, SK-BR-3, U-87 and U-251) express prothrombin. The prothrombin RNA expression level was assessed by qPCR, and the presence of prothrombin was analyzed by Western blot analysis. Our results show that Caco-2 cells originating from colorectal adenocarcinoma express prothrombin, whereas other analyzed cell lines do not. Our results provide a background for further research into the role of (pro) thrombin in cancer etiopathology.

Background/ Aim: Thrombin plays significant roles in various types of cancer. However, the expression levels of prothrombin, the thrombin precursor, in cancer remain unclear. Variants of the 3'end of the prothrombin gene lead to increased prothrombin expression. This study aimed to analyze prothrombin 3'end gene variants in colon tumor and adjacent normal tissue samples. Materials and Methods: The study group consisted of 93 patients suffering from colon adenocarcinoma. The 3'end of the prothrombin gene was analyzed by DNA sequencing. Results: Three variants, all previously associated with increased prothrombin expression were detected. Frequency of the FII 19911G allele was 46.77% and 47.85% in tumor and normal tissue, respectively. For the FII 20210A allele, the detected frequencies were 2.15% and 1.61%, respectively. The frequency of the FII c.1824T allele was 0.54% in both tissues. Four patients showed different genotypes in tumor and normal tissue. Conclusion: Prothrombin 3' end gene variants may play a role in colorectal cancer.

Breast cancer is the leading cause of cancer-related death among women. An increased burden of thrombotic events among breast cancer patients, leading to higher mortality and morbidity rates, is well established. There are a number of genetic risk factors associated with thrombosis, but their contribution to thrombotic tendencies in patients with cancer is not completely elucidated. We aimed to investigate possible role of FV Leiden, FII G20210A, MTHFR C677T and PAI-1 4G/5G gene variants in etiopathology of breast cancer and accompanying thrombosis in cohort of Serbian patients. Our study included 316 subject divided in three groups: breast cancer patients with (97) or without (99) accompanying thrombosis and healthy control group (120). According to our results, the prevalence for all four prothrombotic gene variants were similar in cancer patients with and without thrombosis and no statistically significant difference was observed between these groups. We detected lower frequency of MTHFR 677TT genotype in breast cancer patients when compared to control group (P=0.014; OR=0.145 (95%CI 0.031-0.679)), indicated that MTHFR C677T homozygosity could play a protective role in breast cancer susceptibility. Our study noted the lack of association between common prothrombotic gene variants and increased prothrombotic risk in Serbian breast cancer patients. Also, our results point out possible role of MTHFR 677TT genotype in etiology of breast cancer, but further studies on larger cohort of patients are needed.

Background: The recently reported c.1787G gt A mutation in the prothrombin gene leads to Arg596Gln replacement in the protein molecule (prothrombin Belgrade). This substitution impairs binding of antithrombin to thrombin and results in inherited thrombophilia, known as antithrombin resistance. Objectives: We aimed to elucidate the clinical and biochemical characteristics of thrombophilia associated with antithrombin resistance in a large Serbian family with the prothrombin Belgrade mutation. Patients and methods: Nineteen family members were investigated, among whom 10 were carriers of the c.1787G gt A mutation. In all subjects the clinical phenotype was determined and laboratory investigations of hemostatic parameters were performed. Results: Six out of the 10 mutation carriers developed thromboembolic events, mainly deep venous and mesenteric vein thrombosis. The median age of the first thrombotic event was 26.5 (12-41) years, whereas the incidence rate of first thrombosis was 2.2% per year. In all mutation carriers prothrombin activity was significantly decreased in comparison with non-carriers, clearly distinguishing each group. However, the presence of the mutation did not affect the prothrombin antigen level in plasma. The endogenous thrombin potential was significantly increased in all carriers in comparison with non-carriers, indicating the presence of blood hypercoagulability. Interestingly, levels of D-dimer and the F1+2 fragment were similar in both groups. Conclusions: Although rare, the prothrombin Belgrade mutation represents strong thrombophilia with early onset of thrombosis in the investigated family. According to our results, decreased prothrombin activity may be a simple screening test for detection of this mutation in thrombotic patients.

The FII c. 1787G gt A (prothrombin Belgrade) is a novel prothrombotic mutation which leads to impaired inhibition of thrombin by antithrombin (antithrombin resistance). So far, the mechanism of this variant has not been fully elucidated. To investigate the effect of FII c. 1787G gt A mutation on the prothrombin gene expression, its functional analysis was performed in vitro. By Real-Time PCR, expression levels of FII gene variants were evaluated in Cos-7 cells transiently transfected with c. 1787G (wild-type) and c. 1787A prothrombin expression vectors, with no differences observed. The relative quantification of prothrombin protein amounts was accomplished by Western blot analysis, also with no differences observed. Therefore, the mechanism of FII c. 1787G gt A mutation does not alter prothrombin expression profile.

Background: Deep vein thrombosis (DVT) represents a common disorder involving genetic and acquired risk factors. It has been proposed that acquired risk factors are more important with aging than genetic factors, indicating different prevalence of prothrombotic mutations throughout the lifespan. Objective: To determine the role of the most frequent prothrombotic genetic risk factors (Factor V [FV] Leiden and Factor II [FII] G20210A mutations) in first-time DVT etiology in patients of different ages. Method: This retrospective study included 701 patients living in Serbia with diagnosed DVT as a first-time thrombotic event. Results: Risk assessment for mutations as age-related markers showed no statistical difference (FV Leiden mutation-OR, 1.027; 95% confidence interval [CI],.87-1.22; P=.76 and FII G20210A mutation-OR, 0.940, 95% CI,.74-1.19; P=.61). Our results show similar mutation prevalence regardless of how old the patients were at the time of the first DVT occurrence. Conclusion: Our results indicate that these 2 mutations cannot be used as prognostic marker for time-to-event first DVT in the Serbian population; however, further studies are required.

Venous thromboembolism is a multifactorial disorder with two manifestations: deep-vein thrombosis and pulmonary embolism. Pulmonary embolism is usually considered as the complication of deep-vein thrombosis, but there are reported cases of isolated pulmonary embolism. FV Leiden and FII G20210A mutations are most common genetic risk factors for the venous thromboembolism. Several studies reported "FV Leiden paradox": lower prevalence of FV Leiden mutation among patients with isolated pulmonary embolism than among those with deep-vein thrombosis. The aim of this study was to determine FV Leiden and FII G20210A mutations frequency in thrombophilic patients in Serbian population. We tested prevalence of these mutations carriers in 1427 individuals divided in three groups of patients (with deep-vein thrombosis, deep-vein thrombosis/pulmonary embolism and isolated pulmonary embolism) and control group. All subjects were tested for these mutations using PCR-RFLP analysis. Detected frequency of FV Leiden heterozygous carriers in patients with isolated pulmonary embolism was 6.9% (for FII G20210A 11.6%), while in other two groups of patients with deep-vein thrombosis and deep vein thrombosis/pulmonary embolism, frequency was 18.6% (for FII G20210A mutation were 11.6% and 8.3%, respectively). Our results showed that FV Leiden mutation is less frequent in patients with isolated pulmonary embolism than in patients with deep-vein thrombosis or deep-vein thrombosis accompanied with pulmonary embolism, confirming "FV Leiden paradox". On the other hand, detected frequency of FII G20210A mutation carriers was similar in all three groups of patients.

Recurrent pregnancy loss (RPL) is a health problem affecting up to 5% of women of reproductive age. Several thrombophilic risk factors might contribute to RPL. To investigate relationship between a novel C20068T gene variant in the 3' end of prothrombin gene and RPL, we tested 153 women with RPL and 111 controls for the presence of this gene variant. In patients, we have detected four heterozygous (2.61%) and no homozygous carriers. In controls, no carriers were detected. Our results indicate higher prevalence of C20068T gene variant in women with RPL but this difference was not statistically significant. However, in patients who suffered 5 or more RPL, frequency of C20068T gene variant was significantly increased compared to controls (12.5% vs. 0%, P = 0.02). This is the first study which points out a possible role of C20068T gene variant in etiology of RPL, but larger studies should be carried out to confirm our findings.

Background: Estimates of the risk ratio of tamoxifen-associated venous thromboembolism(VTE) in breast cancer patients range from 2.4 to 7.1. The occurrence of thrombosis in patients with breast cancer complicates the clinical condition and causes a change of treatment. Our study was conducted in order to investigate the influence of patient-related risk factors for thrombosis development in breast cancer patients whose treatment included adjuvant tamoxifen. Methods: The prospective, single center, case control study included 150 breast cancer women, 50 whom developed venous thrombosis during adjuvant tamoxifen and 100 whom did not have thrombosis, as a control group. Patient-related risk factors such as: age, body mass index, previous VTE, varicose veins, concomitant diseases, the presence of prothrombotic mutations (FV Leiden, FII G20210A) and FVIII activity were evaluated in both groups. Results: In respect of prothrombotic mutations, the FV Leiden mutation was present in a higher number of women from the VTE group (10/50 vs 7/100; P = 0.020). Additionally, FVIII activity was significantly higher in the VTE group; median (IQR), of 1.79 (0.69) vs 1.45 (0.55); P lt 0.001 and more women in this group (24/50 vs 34/100) had increased FVIII activity; P = 0.020. In those women with FVIII gt 1.5 IU/ml, who were carriers of prothrombotic mutations, an OR of 3.76 (CI 95% 1.276-11.096; P = 0.016) was obtained for VTE. Conclusion: The results of our study showed that the factor V Leiden mutation and high FVIII are associated with an increased risk of VTE in women with breast cancer during adjuvant tamoxifen.