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Introduction: Prothrombin deficiency is a very rare disorder caused by mutations in the F2 gene that generate hypoprothrombinemia or dysprothrombinemia and is characterized by bleeding manifestations that can vary from clinically irrelevant to life-threatening., Aim: Here we characterize a patient with a novel missense mutation in F2, c.1090T/A (p.Val322Glu), that causes severe dysprothrombinemia., Methods: Coagulation assays, prothrombin Western Blotting, FII activation by Ecarin, fibrinogen degradation products quantification and thrombin generation assay were carried out to assess prothrombin expression and function. PCR followed by direct sequencing was carried out to characterize the mutation. In silico analysis for missense variant and molecular modeling were applied to predict the mechanism that leads to dysprothrombinemia., Results and Conclusions: The homozygous patient had a markedly prolonged prothrombin time, strongly reduced FII activity (0.82%) but normal antigen levels. In the thrombin generation assay the lag time and the peak height were unmeasurable, suggesting that the Val322Glu mutation results in the inability of the mutant prothrombin to be fully activated to thrombin. In fact, prothrombin activation by ecarin was defective, with a massive accumulation of the meizothrombin intermediate. Molecular modeling and dynamic simulation studies showed that the Val322Glu mutation interferes with protein flexibility at Arg271 and Arg320. This impairs the switch of the protein from zymogen to proteinase, thus preventing the formation of thrombin. Accumulated meizothrombin, however, maintains some fibrinogen-degrading activity, as shown by the formation of FDPs, and this probably explains the patient's mild bleeding phenotype., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Protein Z (PZ) is a vitamin K-dependent factor identified in human plasma in 1984 characterized by an homology with other vitamin K-dependent factors. PZ acts as the cofactor of the PZ dependent inhibitor (ZPI), in the inhibition of activated factor X bound on phospholipid surface. In humans, PZ is characterized by an unusual wide distribution in plasma partly explained by a genetic control. Several PZ gene polymorphisms influencing plasma concentration have been described. In mice, the disruption of PZ gene is asymptomatic, but in association with homozygous FV Leiden produced a severe prothrombotic phenotype. This review analyzes the results obtained from different studies so far published in order to understand whether PZ deficiency could be considered as a risk factor for venous thrombosis. The roles of PZ plasma level and PZ gene polymorphisms remain debated with conflicting results. Many of these studies reported low PZ levels in association with an increased risk of venous thrombosis. On the other side, some studies did not observe an association between low levels of PZ and thrombotic events. A relationship between PZ deficiency and pregnancy complications was also described but not confirmed by all studies. These discrepancies can be explained by the heterogeneity of populations chosen as control, by the PZ interindividual variability and by the small size of the cohorts in mainly retrospective studies. Large prospective studies remain to be done to investigate its possible role in thrombosis., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Background: The JAK2 V617F mutation is an independent risk factor for MPN and SVT. Gender-related differences in MPN distribution have been reported and, recently, variability in the JAK2 V617F allele burden between sexes has been suggested. We wondered whether gender would modulate the role of the JAK2 V617F mutation as susceptibility risk factor for SVT., Materials and Methods: In 180 patients presenting with SVT, medical history was collected. The presence of the JAK2 V617F mutation and 46/1 haplotype was determined by polymerase chain reaction followed by TaqMan SNP genotyping assays., Results: Among patients with SVT, 43 (23.9%; 95%-CI: 18.2-30.7) carried the JAK2 V617F mutation. The JAK2 V617F mutation was found more frequently in women (29/95: 30.5%; 95%-CI: 22.1-40.4) than in men (14/85: 16.5%; 95%-CI: 10.0-25.9; OR: 2.2; 95%-CI: 1.1-4.5). The distribution of 46/1 haplotype frequencies did not differ significantly between men and women. In women carrying the rs12343867 CC genotype, the frequency observed for the occurrence of the V617F mutation was significantly higher than that observed in those not carrying (60.0% [95% CI: 31.2-83.3] vs. 26.8% [95% CI: 18.4-37.4]; OR: 4.1; 95%-CI: 1.1-14.9). In men, a similar prevalence was found among carriers of the rs12343867 CC genotype (16.7% [95% CI: 3.5-46.0]) and in non carriers (16.4% [95% CI: 9.3-27.2]). The V617F allele burden was unrelated to clinical characteristics and significantly higher in carriers of the rs12343867 CC genotype., Conclusions: Present findings suggest that, in patients presenting with SVT, the JAK2 V617F mutation is frequently found in women and, possibly by interacting with the 46/1 haplotype, may represent a gender-related susceptibility allele for SVT., (Copyright © 2011 Elsevier Ltd. All rights reserved.)