The relationship between factor V Leiden, prothrombin G20210A, and MTHFR mutations and the first major thrombotic episode in polycythemia vera and essential thrombocythemia

Recent Advances in the Use of Molecular Analyses to Inform the Diagnosis and Prognosis of Patients with Polycythaemia Vera

Genetic studies in the past decade have improved our understanding of the molecular basis of the BCR-ABL1-negative myeloproliferative neoplasm (MPN) polycythaemia vera (PV). Such breakthroughs include the discovery of the JAK2V617F driver mutation in approximately 95% of patients with PV, as well as some very rare cases of familial hereditary MPN caused by inherited germline mutations. Patients with PV often progress to fibrosis or acute myeloid leukaemia, both associated with very poor clinical outcome. Moreover, thrombosis and major bleeding are the principal causes of morbidity and mortality. As a result of increasingly available and economical next-generation sequencing technologies, mutational studies have revealed the prognostic relevance of a few somatic mutations in terms of thrombotic risk and risk of transformation, helping to improve the risk stratification of patients with PV. Finally, knowledge of the molecular basis of PV has helped identify targets for directed therapy. The constitutive activation of the tyrosine kinase JAK2 is targeted by ruxolitinib, a JAK1/JAK2 tyrosine kinase inhibitor for PV patients who are resistant or intolerant to cytoreductive treatment with hydroxyurea. Other molecular mechanisms have also been revealed, and numerous agents are in various stages of development. Here, we will provide an update of the recent published literature on how molecular testing can improve the diagnosis and prognosis of patients with PV and present recent advances that may have prognostic value in the near future.

Essential Thrombocythemia and Acquired von Willebrand Syndrome: The Shadowlands between Thrombosis and Bleeding

Over the past decade, new insights have emerged on the pathophysiology of essential thrombocythemia (ET), its clinical management, and associated thrombohemostatic disturbances. Here, we review the latest diagnostic and risk stratification modalities of ET and its therapeutics. Moreover, we discuss the clinical evidence-based benefits, deriving from major clinical trials, of using cytoreductive therapy and antiplatelet agents to lower the risk of fatal vascular events. Also, we focus on the condition of extreme thrombocytosis (>1000 × 10⁹/L) and bleeding risk, the development and pathogenesis of acquired von Willebrand syndrome, and the clinical approach to this paradoxical scenario in ET.

Essential thrombocythemia: a hemostatic view of thrombogenic risk factors and prognosis

Essential thrombocythemia (ET) is a classical myeloproliferative neoplasm that is susceptible to hypercoagulable state due to impaired hemostatic system, so that thrombotic complications are the leading cause of mortality in ET patients. The content used in this article has been obtained by the PubMed database and Google Scholar search engine from English-language articles (2000-2019) using the following keywords: "Essential thrombocythemia," "Thrombosis," "Risk factors" and "Hemostasis. In this neoplasm, the count and activity of cells such as platelets, leukocytes, endothelial cells, as well as erythrocytes are increased, which can increase the risk of thrombosis through rising intercellular interactions, expression of surface markers, and stimulation of platelet aggregation. In addition to these factors, genetic polymorphisms in hematopoietic stem cells (HSCs), including mutations in JAK2, CALR, MPL, or genetic abnormalities in other genes associated with the hemostatic system may be associated with increased risk of thrombotic events. Moreover, disruption of coagulant factors can pave the way for thrombogeneration. Therefore, the identification of markers related to cell activation, genetic abnormalities, or alternation in the coagulant system can be used together as diagnostic and prognostic markers for the occurrence of thrombosis among ET patients. Thus, because thrombotic complications are the main factors of mortality in ET patients, a hemostatic viewpoint and risk assessment of cellular, genetic, and coagulation factors can have prognostic value and contribute to the choice of effective treatment and prevention of thrombosis.

Systemic and Local Factors’ Influence on the Topological Differences in Deep Vein Thrombosis

Background and Objectives: Deep vein thrombosis (DVT) is a common cause of intra-hospital morbidity and mortality, and its most severe complication is pulmonary thromboembolism. The risk factors that influence the apparition of DVT are generally derived from Virchow’s triad. Since the most severe complications of DVT occur in proximal rather than distal deep vein thrombosis, the aim of this study was to identify the factors influencing the apparition of proximal DVT. Materials and Methods: This was a transversal, cohort study. The study included 167 consecutive patients with lower limb DVT over a two-year period. The following data were recorded or determined: general data, conditions that are known to influence DVT, medical history and coagulation or thrombophilia-related genetic variations. Results: In the univariate analysis, male gender, neoplasia, previous DVT and mutated factor V Leiden were all associated with proximal DVT, while bed rest was associated with distal DVT. In the multivariate analysis, male gender, previous DVT and factor V Leiden mutation were independently correlated with proximal DVT, while bed rest was independently associated with distal deep vein thrombosis. Conclusion: Our observations point out that the factors indicating a systemic involvement of coagulation were correlated with proximal DVT, while local factors were associated with distal DVT.

Influence of Blood Count, Cardiovascular Risks, Inherited Thrombophilia, and JAK2 V617F Burden Allele on Type of Thrombosis in Patients With Philadelphia Chromosome Negative Myeloproliferative Neoplasms

INTRODUCTION

Thrombosis is the most common complication in Philadelphia chromosome negative (Ph-) myeloproliferative neoplasms patients.

PATIENTS AND METHODS

In a cohort of 258 Ph- myeloproliferative neoplasm patients, the difference between patients with and without thrombosis was analyzed according to genetic thrombophilia factors, JAK2 V617F status and burden allele, blood count, cardiovascular risk factors and age. Patients were also divided in polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) subgroups as well as by the type of thrombosis.

RESULTS

Analysis of cardiovascular risk factors regarding arterial thrombosis showed that PV patients with thrombosis had higher incidence of diabetes (P = .030), ET patients more often had hypertension (P = .003) and hyperlipidemia (P = .005), while PMF patients had hyperlipidemia (P = .046) and at least one cardiovascular risk factor (P = .044). Moreover, leukocytes > 18 × 10⁹/L and V617F burden allele > 25.7% were statistically significantly different in PV patients (P = .019 and borderline significant at P = .055, respectively), while in ET patients leukocytes > 9.2 × 10⁹/L (P < .001) and age at diagnosis of > 55 years were statistically significantly different (P = .002). PMF patients with V617F burden allele ≤ 34.8% were more prone to thrombosis (P = .032). When comparing patients with and without venous thrombosis, cutoff value of V617F burden allele > 90.4% was significant for PV patients with thrombosis (P = .036), as was > 56.7% for PMF patients with thrombosis (P = .046). Platelets ≤ 536 × 10⁹/L and age at diagnosis > 54 years showed statistically significant difference for ET patients with thrombosis (P = .015 and P = .041, respectively).

CONCLUSION

On the basis of our results, a new scoring system for thrombosis risk in PV could be made, while PMF prognostic model may be expanded for better recognition of potential thrombotic risk factors.

Cerebral thrombosis and myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are acquired clonal disorders characterized by the proliferation of bone marrow myeloid cells. Different somatic mutations have been recently associated with MPN, the most common being JAK-2 V617F. Among MPN, polycythemia vera and essential thrombocythemia are particularly associated with an increased risk to develop thrombotic complications, either arterial or venous. Cerebrovascular events (stroke and transient ischemic attacks) are prevalent, accounting for approximately two-thirds of all events. Also cerebral vein thrombosis can complicate MPN and can be the first manifestation of the disease. Risk factors for thrombosis in patients with MPN are related or unrelated to the disease. Among the former there are cellular risk factors, such as increased white blood cell counts, vascular cell activation, endothelial dysfunction, and plasmatic risk factors, such as increased plasma viscosity, reduced levels of protein S, increased thrombin generation. The latter include increased age and previous thrombotic events. In addition, common cardiovascular risk factors (smoking, hypertension, diabetes, dyslipidemia, obesity) contribute to the pathogenesis of arterial events, whereas circumstantial risk factors (particularly oral contraceptive use and pregnancy/puerperium) to that of venous events. Primary prevention of arterial thrombosis with antiplatelet therapy is warranted in the majority of patients with MPN, whereas primary prevention of venous thrombosis is limited to anticoagulant prophylaxis during high-risk situations. Secondary prevention includes long-term antiplatelet therapy for arterial and short- or long-term anticoagulant therapy for venous thrombosis, depending on the risk factors present at the first event.