How I treat essential thrombocythemia

A Case of acute Myocardial Infarction in a Patient with Essential Thrombocythaemia Treated with Anagrelide

Anagrelide is a medication primarily used to manage thrombocytosis, an abnormal increase in platelet levels in the blood. It is often prescribed for patients with myeloproliferative disorders, such as essential thrombocythaemia (ET). Given the heightened susceptibility to thromboembolism associated with this condition, the primary emphasis in treatment revolves around reducing the risk of thrombotic events through the administration of cytotoxic agents. While anagrelide is generally effective in reducing platelet counts, it comes with potential side effects, including an increased risk of certain thrombotic events. Anagrelide acts by inhibiting megakaryocyte maturation and platelet release, thereby reducing platelet production. However, this platelet-lowering effect may be accompanied by an increase in platelet activation and reactivity, which could contribute to a prothrombotic state. We present a case of a 60-year-old female with a history of ET, managed with anagrelide and hydroxyurea therapy, who experienced an acute ST-elevation myocardial infarction.

LEARNING POINTS

The dual role of anagrelide: although anagrelide is effective in lowering platelet levels in essential thrombocythaemia, it can increase platelet activation, raising thrombotic risk. Clinicians need to monitor patients closely for thrombotic events.Balancing efficacy and side effects: the risk of severe side effects such as myocardial infarction, as seen in this case report, necessitates a balanced approach in using anagrelide, weighing its benefits against potential risks.

Prodrug approaches for the development of a long-acting drug delivery systems

Long-acting formulations are designed to reduce dosing frequency and simplify dosing schedules by providing an extended duration of action. One approach to obtain long-acting formulations is to combine long-acting prodrugs (LA-prodrug) with existing or emerging drug delivery technologies (DDS). The design criteria for long-acting prodrugs are distinct from conventional prodrug strategies that alter absorption, distribution, metabolism, and excretion (ADME) parameters. Our review focuses on long-acting prodrug delivery systems (LA-prodrug DDS), which is a subcategory of long-acting formulations where prodrug design enables DDS formulation to achieve an extended duration of action that is greater than the parent drug. Here, we define LA-prodrugs as the conjugation of an active pharmaceutical ingredient (API) to a promoiety group via a cleavable covalent linker, where both the promoiety and linker are selected to enable formulation and administration from a drug delivery system (DDS) to achieve an extended duration of action. These LA-prodrug DDS results in an extended interval where the API is within a therapeutic range without necessarily altering ADME as is typical of conventional prodrugs. The conversion of the LA-prodrug to the API is dependent on linker cleavage, which can occur before or after release from the DDS. The requirement for linker cleavage provides an additional tool to prolong release from these LA-prodrug DDS. In addition, the physicochemical properties of drugs can be tuned by promoiety selection for a particular DDS. Conjugation with promoieties that are carriers or amenable to assembly into carriers can also provide access to formulations designed for extending duration of action. LA-prodrugs have been applied to a wide variety of drug delivery strategies and are categorized in this review by promoiety size and complexity. Small molecule promoieties (typically MW < 1000 Da) have been used to improve encapsulation or partitioning as well as broaden APIs for use with traditional long-acting formulations such as solid drug dispersions. Macromolecular promoieties (typically MW > 1000 Da) have been applied to hydrogels, nanoparticles, micelles, dendrimers, and polymerized prodrug monomers. The resulting LA-prodrug DDS enable extended duration of action for active pharmaceuticals across a wide range of applications, with target release timescales spanning days to years.

Megakaryocyte Diversity in Ontogeny, Functions and Cell-Cell Interactions

Hematopoietic stem cells (HSCs) rely on local interactions in the bone marrow (BM) microenvironment with stromal cells and other hematopoietic cells that facilitate their survival and proliferation, and also regulate their functions. HSCs and multipotent progenitor cells differentiate into lineage-specific progenitors that generate all blood and immune cells. Megakaryocytes (Mks) are hematopoietic cells responsible for producing blood platelets, which are essential for normal hemostasis and blood coagulation. Although the most prominent function of Mks is platelet production (thrombopoiesis), other increasingly recognized functions include HSC maintenance and host immune response. However, whether and how these diverse programs are executed by different Mk subpopulations remains poorly understood. This Perspective summarizes our current understanding of diversity in ontogeny, functions and cell-cell interactions. Cumulative evidence suggests that BM microenvironment dysfunction, partly caused by mutated Mks, can induce or alter the progression of a variety of hematologic malignancies, including myeloproliferative neoplasms (MPNs) and other disorders associated with tissue scarring (fibrosis). Therefore, as an example of the heterogeneous functions of Mks in malignant hematopoiesis, we will discuss the role of Mks in the onset and progression of BM fibrosis. In this regard, abnormal interactions between of Mks and other immune cells might directly contribute to fibrotic diseases. Overall, further understanding of megakaryopoiesis and how Mks interact with HSCs and immune cells has potential clinical implications for stem cell transplantation and other therapies for hematologic malignancies, as well as for treatments to stimulate platelet production and prevent thrombocytopenia.

Myeloproliferative neoplasms treated with hydroxyurea, pegylated interferon alpha-2A or ruxolitinib: clinicohematologic responses, quality-of-life changes and safety in the real-world setting

Introduction: Real-world data of responses, quality-of-life (QOL) changes and adverse events in patients with myeloproliferative neoplasms (MPN) on conventional therapy (hydroxyurea ± anagrelide), pegylated interferon alpha-2A (PEG-IFNα-2A) or ruxolitinib are limited. Methods: We prospectively studied MPN patients receiving conventional therapy, PEG-IFNα-2A or ruxolitinib. Next-generation sequencing of 69 myeloid-related genes was performed. Clinicohematologic responses, adverse events, and QOL (determined by the Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score, MPN-SAF TSS) were evaluated. Results: Seventy men and fifty-five women with polycythemia vera (PV) (N = 23), essential thrombocythemia (ET) (N = 56) and myelofibrosis (MF) (N = 46) were studied for a median of 36 (range: 19-42) months. In PV, responses were comparable for different modalities. CREBBP mutations were associated with inferior responses. In ET, PEG-IFNα-2A resulted in superior clinicohematologic complete responses (CHCR) (P = 0.045). In MF, superior overall response rates (ORR) were associated with ruxolintib (P = 0.018) and JAK2V617F mutation (P = 0.04). For the whole cohort, ruxolitinib led to rapid and sustained reduction in spleen size within the first 6 months, and significant improvement of QOL as reflected by reduction in MPN-SAF TSS (P < 0.001). Adverse events of grades 1-2 were observed in 44%, 62% and 20% of patients receiving conventional therapy, PEG-IFNα-2A and ruxolitinib respectively; and of grade 3-4 in 7% and 9% of patients receiving PEG-IFNα-2A and ruxolitinib. Conclusions: Conventional therapy, PEG-IFNα-2A and ruxolitinib induced responses in all MPN subtypes. PEG-IFNα-2A led to superior CHCR in ET; whereas ruxolitinib resulted in superior ORR in MF, and significant reduction in spleen size and improvement in QOL.

Cardiac Surgery Using Hypothermic Circulatory Arrest in a Case of Essential Thrombocythemia

We present the case of a 61-year-old patient with a history of essential thrombocythemia (ET) who was diagnosed as having aortic valve stenosis and dilatation of his ascending aorta. His aortic valve and ascending aorta were replaced under hypothermic circulatory arrest (HCA). No clear guideline exists for preoperative, perioperative, and postoperative management of cardiac surgery using HCA for ET patients. After performing risk assessment, we prescribed preoperative aspirin therapy and postoperative care was planned as usual for cardiovascular surgery in our establishment. Unexpectedly, activated clotting time did not exceed 400 seconds, but the course of treatment was otherwise uneventful.

How we manage Philadelphia-negative myeloproliferative neoplasms in pregnancy

The combined incidence of classical Philadelphia-negative myeloproliferative neoplasm (MPN) is 6-9/100 000 with a peak frequency between 50 and 70 years. MPN is less frequent in women of reproductive age. However, for essential thrombocythaemia (ET) in particular there is a second peak in women of reproductive age and 15% of polycythaemia vera (PV) patients are less than 40 years of age at the time of diagnosis. Thus these diseases are encountered in women of reproductive potential and may be diagnosed in pregnancy or in women being investigated for recurrent pregnancy loss. The incidence of MPN pregnancies is 3·2/100 000 maternities per year in the UK. The majority of data regarding Philadelphia-negative MPNs relates to patients with ET, for which the literature suggests significant maternal morbidity and poor fetal outcome; specifically maternal thrombosis and haemorrhage, miscarriage, pre-eclampsia, intrauterine growth restriction (IUGR), stillbirth and premature delivery as summarised in the recent systematic review and meta-analysis in Blood, 2018, 132, 3046. The literature for PV is more sparse but increasing and is concordant with ET pregnancy outcomes. The literature regarding primary myelofibrosis (PMF) is even more scarce. Treatment options include aspirin, venesection, low molecular weight heparin (LMWH) and cytoreductive therapy. Data and management recommendations are often extrapolated from other pro-thrombotic conditions or from ET to PV and PMF. Women of reproductive age with a diagnosis of MPN should receive information and assurance regarding management and outcome of future pregnancies. From pre-conceptual planning to the post-partum period, women should have access to joint care from an obstetrician with experience of high-risk pregnancies and a haematologist in a multidisciplinary setting. This paper provides an update with regards to Philadelphia-negative MPN in pregnancy, details local practise in an internationally recognised centre for patients with MPN and outlines a future research strategy.

Platelet Function Tests and Inflammatory Markers for the Differentiation of Primary Thrombocytosis and Secondary Thrombocytosis

Background:

The prognosis and management of primary thrombocytosis (PT) and secondary thrombocytosis (ST) are different. This study aims to evaluate the role of platelet function tests by light transmission platelet aggregometry (LTA), plasma von Willebrand factor antigen (vWF:Ag), ristocetin cofactor activity (vWF:RCo) and inflammatory markers [erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)] for the differentiation between PT and ST.

Methods:

This prospective study was carried out in patients with platelet counts greater than 450 x 109/L. Primary outcomes were the sensitivity and specificity of platelet function tests by LTA for the differentiation of PT and ST. Secondary outcomes were sensitivity and specificity of ESR, CRP, vWF:Ag, and vWF:RCo for the differentiation of PT and ST.

Results:

Fifty-two patients were enrolled onto the study of which 26 (50%) had PT. The sensitivity and specificity of epinephrine, collagen, and arachidonic acid (AA) induced abnormal LTA for the differentiation of PT from ST were sensitivity of 50%, 38.5%, 26.9% and specificity of 88.5%, 100%, 100% respectively. The sensitivity and specificity of abnormal ESR, CRP, and either abnormal ESR or CRP in the differentiation of ST from PT were sensitivity of 88.5%, 80.8%, 100% and specificity of 65.4%, 61.5%, 46.2% respectively. The sensitivity and specificity of low vWF:Ag and vWF:RCo in the differentiation of PT from ST were sensitivity of 7.69%, 42.3% and specificity of 100%, 88.5% respectively.

Conclusions:

Abnormal platelet function determined by LTA with collagen, AA, epinephrine had high specificity ratings enabling the differentiation between PT and ST. vWF:RCo, ESR and CRP levels could be helpful in differentiating between PT and ST.

How I treat polycythemia vera

Since its discovery, polycythemia vera (PV) has challenged clinicians responsible for its diagnosis and management and scientists investigating its pathogenesis. As a clonal hematopoietic stem cell (HSC) disorder, PV is a neoplasm but its driver mutations result in overproduction of morphologically and functionally normal blood cells. PV arises in an HSC but it can present initially as isolated erythrocytosis, leukocytosis, thrombocytosis, or any combination of these together with splenomegaly or myelofibrosis, and it can take years for a true panmyelopathy to appear. PV shares the same JAK2 mutation as essential thrombocytosis and primary myelofibrosis, but erythrocytosis only occurs in PV. However, unlike secondary causes of erythrocytosis, in PV, the plasma volume is frequently expanded, masking the erythrocytosis and making diagnosis difficult if this essential fact is ignored. PV is not a monolithic disorder: female patients deregulate fewer genes and clinically behave differently than their male counterparts, while some PV patients are genetically predisposed to an aggressive clinical course. Nevertheless, based on what we have learned over the past century, most PV patients can lead long and productive lives. In this review, using clinical examples, I describe how I diagnose and manage PV in an evidence-based manner without relying on chemotherapy.

Platelet count abnormalities and peri-operative outcomes in adults undergoing elective, non-cardiac surgery

Background

Anemia and transfusion of blood in the peri-operative period have been shown to be associated with increased morbidity and mortality across a wide variety of non-cardiac surgeries. While tests of coagulation, including the platelet count, have frequently been used to identify patients with an increased risk of peri-operative bleeding, results have been equivocal. The aim of this study was to assess the effect of platelet level on outcomes in patients undergoing elective surgery.

Materials and methods

Retrospective cohort analysis of prospectively-collected clinical data from American College of Surgeons National Surgical Quality Improvement Program (NSQIP) between 2006–2016.

Results

We identified 3,884,400 adult patients who underwent elective, non-cardiac surgery from 2006–2016 at hospitals participating in NSQIP, a prospectively-collected, national clinical database with established reproducibility and validity. After controlling for all peri- and intraoperative factors by matching on propensity scores, patients with all levels of thrombocytopenia or thrombocytosis had higher odds for perioperative transfusion. All levels of thrombocytopenia were associated with higher mortality, but there was no association with complications or other morbidity after matching. On the other hand, thrombocytosis was not associated with mortality; but odds for postoperative complications and 30-day return to the operating room remained slightly increased after matching.

Conclusions

These findings may guide surgeons in the appropriate use and appreciation of the utility of pre-operative screening of the platelet count prior to an elective, non-cardiac surgery.

Recurrent ischaemic cerebrovascular events as presenting manifestations of myeloproliferative neoplasms

BACKGROUND AND PURPOSE

Myeloproliferative neoplasms (MPNs) - polycythemia vera, essential thrombocythemia and primary myelofibrosis - are associated with increased risk for ischaemic cerebrovascular events (ICVEs). Due to their low prevalence, MPNs often remain undiagnosed as the cause of ICVEs.

METHODS

Case records at the University of Tübingen between 2014 and 2017 were screened to identify patients with MPN-related ICVEs. Clinical features, brain imaging, laboratory findings, applied treatments and neurological outcomes were assessed.

RESULTS

In all, 3318 patients with ICVEs were identified, and amongst them 17 patients with MPN-related ICVEs were included in a retrospective study. In 58% of these patients, ICVEs were the first manifestation of the underlying MPN; 24% presented with transient ischaemic attack and 76% with ischaemic stroke. Potentially concurrent ICVE etiologies were noted in 70% of the patients. The majority (94%) of patients were positive for the JAK2 V617F mutation, whilst in 29% recurrent ICVEs (range two to three) were noted prior to MPN diagnosis. Early MPN diagnosis and management was the only significant prognostic factor for ICVE recurrence (P < 0.001).

DISCUSSION

Evidence is provided that, although rare, MPNs represent an underdiagnosed cause of recurrent ICVEs. High clinical awareness is warranted to identify an underlying MPN in patients presenting with sustained, abnormal blood count findings. Clinical algorithms for prompt MPN diagnosis and initiation of MPN treatment (e.g. cytoreductive therapy, phlebotomy) are required. As MPN management comprises a significant protective factor against ICVE recurrence, induction of MPN treatment should be regarded as an integral component of secondary stroke prevention in MPN-associated ICVEs.

The course of acquired von Willebrand syndrome during pregnancy among patients with essential thrombocytosis

To investigate the course of acquired type 2A von Willebrand syndrome (AVWS) in relation to patient management and outcomes among pregnant patients with essential thrombocytosis (ET). A review of pregnant women with ET evaluated for AVWS at the beginning of pregnancy and at the third trimester. Eighteen women with 24 pregnancies were included in this study. A history of bleeding was noted in 8 (44%) patients. In 20 (83%) pregnancies AVWS was evident at the initial testing. Following initial testing, antithrombotic therapy was administered in 22 (92%) pregnancies (aspirin, n = 20 and low-molecular-weight heparin, n = 2). In the remaining two pregnancies, VWF:RCo levels were below 30%; thus, aspirin was given only after repeat testing at 14-16 weeks. At third trimester testing, median VWF:RCo levels were significantly higher than at the initial testing (86 vs. 48%, P < 0.001), with no evidence of AVWS in any of the patients. Significant increases were also observed in the VWF:Ag level (127 vs. 84%, P < 0.001), the VWF:RCo/VWF:Ag ratio (0.75 vs. 0.54, P < 0.001) and the FVIII level (103 vs. 68%, P < 0.001); while platelet count (359 vs. 701 × 10⁹/l, P < 0.001) and hemoglobin level (11.6 vs. 13.4 g/dl, P < 0.001) decreased. Neuraxial anesthesia was safely performed in 17 (71%) pregnancies. No significant bleeding events occurred during pregnancy and delivery. AVWS-related abnormalities in women with ET mostly improved during pregnancy, with favorable maternal and fetal outcomes. VWF parameters should be tested at early pregnancy and repeated at the third trimester, to guide pregnancy and delivery management.

Coexistent Breast Cancer and Essential Thrombocythemia: How We Addressed the Therapeutic Challenges

Essential thrombocythemia (ET) occurring with breast cancer is uncommon; the therapeutic approach varies and poses a challenge. A 65-year-old female presented to us after being diagnosed with hormone positive, HER2-negative infiltrating ductal carcinoma. She had a platelet count of 600 thou/cu mm. Her JAK2 mutation was positive. Bone marrow biopsy showed increased megakaryocytes. She was diagnosed with ET in the setting of breast cancer. She underwent breast conservation surgery after which aspirin was resumed. Anticipating thrombocytopenia during chemotherapy and given the absence of data combining hydroxyurea with standard chemotherapy used for breast cancer, we felt it prudent to delay cytoreductive therapy for her ET until after completion of breast cancer treatment. Her average platelet count during chemotherapy was 480 thou/cu mm with the lowest being 377 thou/cu mm. Her platelet count remained at goal between 300 and 350 thou/cu mm after four months of hydroxyurea.

Contemporary management of patients with BCR-ABL1-negative myeloproliferative neoplasms during pregnancy

INTRODUCTION

The management of pregnancy during the course of BCR-ABL1-negative myeloproliferative neoplasms (MPN) is an increasingly relevant problem. This is mostly due to earlier and better diagnosis of MPN together with the trend in modern society toward delaying pregnancy until later life. Areas Covered: The present review aims to provide an overview of the available literature data concerning outcome of pregnancy in MPN. Possible therapeutic modalities are discussed and a management algorithm is suggested. Expert Commentary: Most data are available for women with essential thrombocythemia and we present 793 published pregnancies. Live birth rate is 68.5% with 31.5% miscarriages. Spontaneous abortion is the most frequent complication with 26.5%, followed by stillbirth with 4.8%. Maternal complications are relatively low with 1.8% major thrombotic and 2.4% major bleeding events. In polycythemia vera the situation is clinically more complex and roughly 150 pregnancy reports are available. There is very limited information in primary myelofibrosis with less than 20 reported pregnancies. With active management including control of blood counts, aspirin, low molecular weight heparin and in higher risk cases interferon alpha pregnancy in MPN is manageable with a success rate not far below the normal situation with 80%.

Essential thrombocythemia presenting as acute coronary syndrome: case reports and literature review

For the patients with essential thrombocythemia (ET), systemic thrombosis presents as one of the most dangerous complications. It's been widely accepted that acute coronary syndrome (ACS) is a kind of thrombotic diseases. However, there are very few case reports about ET first presenting as ACS. For some patients diagnosed as ACS, but without markedly elevated platelet, underlying ET was missed. And there are some controversies in the principles and target of treatment in those patients. We reported three cases of ACS, in which the patients who did not have common risk factors for coronary artery diseases and presented only mild atherosclerotic stenosis during coronary angiography, one of which had recurrent coronary artery thrombosis. Noticing their elevated blood platelet level and characteristics in angiography, diagnosis of ET was made according to bone marrow morphology and genetic tests. Although they had only mild thrombocytosis, we applied intensive treatment with dual anti-platelet therapy combined with cytoreduction in addition to early coronary intervention, having satisfying outcomes. During the diagnosis and treatment of ACS, if patients present thrombocytosis, but lack common coronary disease risk factors and thrombotic coronary artery occlusion, cardiologists should search for possible ET as an underlying cause of thrombotic coronary event. All those patients were high-risk according to ET risk stratification. Treatment of cytoreduction in combination with anti-thrombosis therapy and revascularization are beneficial. Treatment aims at the target of complete response with platelet count below 400 × 10⁹/L.

Mutant calreticulin knockin mice develop thrombocytosis and myelofibrosis without a stem cell self-renewal advantage

Somatic mutations in the endoplasmic reticulum chaperone calreticulin (CALR) are detected in approximately 40% of patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF). Multiple different mutations have been reported, but all result in a +1-bp frameshift and generate a novel protein C terminus. In this study, we generated a conditional mouse knockin model of the most common CALR mutation, a 52-bp deletion. The mutant novel human C-terminal sequence is integrated into the otherwise intact mouse CALR gene and results in mutant CALR expression under the control of the endogenous mouse locus. CALRdel/+ mice develop a transplantable ET-like disease with marked thrombocytosis, which is associated with increased and morphologically abnormal megakaryocytes and increased numbers of phenotypically defined hematopoietic stem cells (HSCs). Homozygous CALRdel/del mice developed extreme thrombocytosis accompanied by features of MF, including leukocytosis, reduced hematocrit, splenomegaly, and increased bone marrow reticulin. CALRdel/+ HSCs were more proliferative in vitro, but neither CALRdel/+ nor CALRdel/del displayed a competitive transplantation advantage in primary or secondary recipient mice. These results demonstrate the consequences of heterozygous and homozygous CALR mutations and provide a powerful model for dissecting the pathogenesis of CALR-mutant ET and PMF.

Myeloproliferative neoplasms: from origins to outcomes

Substantial progress has been made in our understanding of the pathogenetic basis of myeloproliferative neoplasms. The discovery of mutations in JAK2 over a decade ago heralded a new age for patient care as a consequence of improved diagnosis and the development of therapeutic JAK inhibitors. The more recent identification of mutations in calreticulin brought with it a sense of completeness, with most patients with myeloproliferative neoplasm now having a biological basis for their excessive myeloproliferation. We are also beginning to understand the processes that lead to acquisition of somatic mutations and the factors that influence subsequent clonal expansion and emergence of disease. Extended genomic profiling has established a multitude of additional acquired mutations, particularly prevalent in myelofibrosis, where their presence carries prognostic implications. A major goal is to integrate genetic, clinical, and laboratory features to identify patients who share disease biology and clinical outcome, such that therapies, both existing and novel, can be better targeted.

Myeloproliferative neoplasms: from origins to outcomes

Substantial progress has been made in our understanding of the pathogenetic basis of myeloproliferative neoplasms. The discovery of mutations in JAK2 over a decade ago heralded a new age for patient care as a consequence of improved diagnosis and the development of therapeutic JAK inhibitors. The more recent identification of mutations in calreticulin brought with it a sense of completeness, with most patients with myeloproliferative neoplasm now having a biological basis for their excessive myeloproliferation. We are also beginning to understand the processes that lead to acquisition of somatic mutations and the factors that influence subsequent clonal expansion and emergence of disease. Extended genomic profiling has established a multitude of additional acquired mutations, particularly prevalent in myelofibrosis, where their presence carries prognostic implications. A major goal is to integrate genetic, clinical, and laboratory features to identify patients who share disease biology and clinical outcome, such that therapies, both existing and novel, can be better targeted.

Genomic profile of a patient with triple negative essential thrombocythemia, unresponsive to therapy: A case report and literature review

Clonal analysis of patients with triple negative myeloproliferative neoplasm (MPN) has provided evidence of additional aberrations, including epigenetic alterations. To discover such novel genetic aberrations, patients were screened through next-generation sequencing using a myeloid sequencing panel of 54 genes using a genetic analyser. Genetic variants in 28 genes, including TET2, BCOR, BCR, and ABL1 were identified in a triple negative essential thrombocythemia (ET) patient. The individual role of some of these variants in disease pathogenesis has yet to be studied. Somatic mutations in the same genes have been reported with variable frequencies in myeloid malignancies. However, no pathogenic impact of these variants could be found; therefore, long-term follow up of patients with genetic analysis of a large cohort and the use of whole genome sequencing is required to assess the effects of these variants.

Medical Management of Extensive Arterial Thromboembolism in a Patient with Essential Thrombocythemia and Warfarin Failure

Chronic myeloproliferative disorders share a stem cell-derived clonal myeloproliferation. This group of disorders include essential thrombocythemia (ET), polycythemia vera (PV), chronic myeloid leukemia, and primary myelofibrosis (PMF), with the respective features of thrombocytosis, erythrocytosis, and bone marrow fibrosis. These disorders can be associated with genetic mutations affecting protein tyrosine kinases, resulting in different configurations of abnormal signal transduction. The Janus tyrosine kinase 2 mutation can be used as a key diagnostic tool for diagnosing MPDs, specifically, ET, PV, and PMF. Patients with ET and PV are at an increased risk for thromboembolic and hemorrhagic events. We present a unique case of ET causing extensive arterial thromboembolism, despite being on adequate antithrombotic agents including warfarin and aspirin.

Molecular determinants of pathogenesis and clinical phenotype in myeloproliferative neoplasms

The myeloproliferative neoplasms are a heterogeneous group of clonal disorders characterized by the overproduction of mature cells in the peripheral blood, together with an increased risk of thrombosis and progression to acute myeloid leukemia. The majority of patients with Philadelphia-chromosome negative myeloproliferative neoplasms harbor somatic mutations in Janus kinase 2, leading to constitutive activation. Acquired mutations in calreticulin or myeloproliferative leukemia virus oncogene are found in a significant number of patients with essential thrombocythemia or myelofibrosis, and mutations in numerous epigenetic regulators and spliceosome components are also seen. Although the cellular and molecular consequences of many of these mutations remain unclear, it seems likely that they interact with germline and microenvironmental factors to influence disease pathogenesis. This review will focus on the determinants of specific myeloproliferative neoplasm phenotypes as well as on how an improved understanding of molecular mechanisms can inform our understanding of the disease entities themselves.

Do we need antiplatelet therapy in thrombocytosis? Contra. Proposal for an individualized risk-adapted treatment

Thrombocytosis is a frequent laboratory finding but not a diagnosis. Therefore, elevated platelet counts (>450 x 10⁹/l) require careful diagnostic work-up to differentiate between reactive thrombocytosis (RT), caused by various conditions, and essential thrombocythemia (ET), a myeloproliferative neoplasm (MPN). In either setting, aspirin is widely used in clinical practice. However, RT (even at platelet counts >1000 x 10⁹/l) has never been shown to cause thrombosis or bleeding due to acquired von Willebrand factor defects in association with high platelet counts. Identification of reactive conditions and appropriate therapy of the underlying disorder are most relevant. By contrast to RT, ET and related MPN can be associated with thrombosis and/or hemorrhage. Current recommendations suggest the use of low-dose aspirin in all patients with ET unless contraindicated. However, the strength of this recommendation is weak, i. e. evidence level IIb grade B. A potential benefit of aspirin used for primary thromboprophylaxis in ET is mostly derived from the ECLAP study in polycythemia vera (PV). However, translating study results from PV to ET appears to be highly questionable and may be biased. In the absence of robust data regarding the benefit-risk balance of aspirin in ET, it appears reasonable (1) to stratify patients according to their individual thrombotic and bleeding risk, (2) to restrict the use of aspirin to high-risk categories and patients with microcirculatory disturbances, (3) to test for pharmacological efficacy (COX-1 inhibition; measurement of TXB₂), and (4) to modify the aspirin dosing regimen (twice instead of once daily) if required.

Acute promyelocytic leukemia co-existing with JAK2 V617F positive myeloproliferative neoplasm: a case report

The V617F mutation of Janus-associated kinase 2 (JAK2) is commonly seen in myeloproliferative neoplasms (MPN). Transformation of JAK2 positive MPNs to acute leukemia has been reported. We here report a case of acute promyelocytic leukemia which was later confirmed to have a co-existing JAK2 V617F positive MPN. In addition, the patient was found to have FLT3-TKD mutation, which, together with PML/RARa, could play a role in the MPN transformation to APL.

Diagnosis, prevention, and management of bleeding episodes in Philadelphia-negative myeloproliferative neoplasms: recommendations by the Hemostasis Working Party of the German Society of Hematology and Medical Oncology (DGHO) and the Society of Thrombosis and Hemostasis Research (GTH)

Philadelphia-negative myeloproliferative neoplasms (Ph-negative MPN) comprise a heterogeneous group of chronic hematologic malignancies. The quality of life, morbidity, and mortality of patients with MPN are primarily affected by disease-related symptoms, thromboembolic and hemorrhagic complications, and progression to myelofibrosis and acute leukemia. Major bleeding represents a common and important complication in MPN, and the incidence of such bleeding events will become even more relevant in the future due to the increasing disease prevalence and survival of MPN patients. This review discusses the causes, differential diagnoses, prevention, and management of bleeding episodes in patients with MPN, aiming at defining updated standards of care in these often challenging situations.

Clinical prognostic factors and outcomes of essential thrombocythemia when transformed to myelodysplastic syndromes and acute myeloid leukemia

Transformation of essential thrombocythemia (ET) to myelodysplastic syndromes or acute myeloid leukemia is infrequent, comprising 1-5% of cases with dismal clinical outcome. Studies on prognosis in ET patients with leukemic transformation are limited. The large cohort included 40 patients (1990-2014) with ET transformation (median age of 59 years, M:F of 1:1). Median time from ET diagnosis to transformation was 76 months (26-481) with median follow-up time of 15 years. Advanced age, myelofibrosis (grade 2-3), and leukocytosis at the time of transformation were associated with inferior OS from transformation (p<0.05). Given rarity of the clinical scenario, multicenter efforts are encouraged.

Thrombotic risk assessment in 185 WHO-defined essential thrombocythemia patients: single center experience

Thrombosis risk in essential thrombocythemia (ET) patients can be assessed using different prognostic systems. Conventional risk factors include age more than 60 years and history of previous thrombosis. In addition, other factors such as JAK2 V617F mutations, cardiovascular risk factors, leukocytosis more than 11 × 10⁹/l, thrombophilic factors and platelet count more than 1500 × 10⁹/l are used in different hematology centers as high-risk features for thrombosis. Our study compared different risk model groups for thrombosis in 185 WHO-defined ET patients at the Hospital of Lithuanian University of Health Sciences Kaunas Klinikos. We found that patient distribution in low, intermediate- and high-risk groups varies using different risk stratification models. The biggest difference in risk assignment is evident in patients who are older than 60 years and have no other risk factors and in patients who are younger than 60 years but have other risk factors.

This observation suggests that new prospective randomized clinical trials are needed to better stratify patients at risk for thrombosis.

MPNs as Inflammatory Diseases: The Evidence, Consequences, and Perspectives

In recent years the evidence is increasing that chronic inflammation may be an important driving force for clonal evolution and disease progression in the Philadelphia-negative myeloproliferative neoplasms (MPNs), essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF). Abnormal expression and activity of a number of proinflammatory cytokines are associated with MPNs, in particular MF, in which immune dysregulation is pronounced as evidenced by dysregulation of several immune and inflammation genes. In addition, chronic inflammation has been suggested to contribute to the development of premature atherosclerosis and may drive the development of other cancers in MPNs, both nonhematologic and hematologic. The MPN population has a substantial inflammation-mediated comorbidity burden. This review describes the evidence for considering the MPNs as inflammatory diseases, A Human Inflammation Model of Cancer Development, and the role of cytokines in disease initiation and progression. The consequences of this model are discussed, including the increased risk of second cancers and other inflammation-mediated diseases, emphasizing the urgent need for rethinking our therapeutic approach. Early intervention with interferon-alpha2, which as monotherapy has been shown to be able to induce minimal residual disease, in combination with potent anti-inflammatory agents such as JAK-inhibitors is foreseen as the most promising new treatment modality in the years to come.

Neurological symptoms in essential thrombocythemia: impact of JAK2V617F mutation and response to therapy

Patients with essential thrombocythemia (ET) often suffer from neurological symptoms (NS) not ever resulting from previous thrombotic cerebral events (TCE). We reported NS occurred in 282 patients, in order to identify the factors influencing ET-related NS in the absence of TCE, and the response to therapy. Overall, 116 of 282 patients (41%) presented NS; 101 of them (87%) reported subjective transient and fluctuating NS, without concurrent TCE, which we defined as ET-related NS, by frequency: cephalalgia, chronic paresthesias, dizziness or hypotension, visual disturbances, and tinnitus. In univariate analysis, ET-related NS resulted more frequently in young people (P = 0.017) and in females (P = 0.025). We found a higher prevalence of JAK2V617F mutation in ET-related NS patients (P = 0.021). In multivariate analysis, gender (P = 0.024) and JAK2V617F mutation (P = 0.041) remained significantly associated with the development of ET-related NS, with a risk of about four times higher for JAK2V617F-mutated patients (OR = 3.75). Ninety-seven of 101 patients with ET-related NS received an antiplatelet (AP) agent at the time of NS, whereas only selected high-risk ET-related NS patients were treated with a cytoreductive drug, according to the published guidelines and similarly to patients without NS. We observed that only 32 of 97 (33%) patients with ET-related NS achieved a complete response after AP treatment. Among the 65 non-responder patients, 36 (55.4%) improved NS after the introduction of cytoreductive therapy; therefore, the addition of cytoreductive treatment should be considered in this setting.

inv (4)(p13q13) in patient with essential thrombocythemia: A case report

The inv (4)(p13q13) cytogenetic abnormality is uncommon in hematologic malignancies. So far, it has not been previously reported in patients with essential thrombocythemia (ET). We report a first case of ET with inv (4)(p13q13) karyotype in a 69-year-old female patient who developed myelofibrosis at follow up. Conventional cytogenetic analysis from a bone marrow sample showed 46, XX, inv (4)(p13q13) [3]/46, XX [4] at diagnosis and subsequent analysis revealed the same abnormal karyotype during the myelofibrosis phase (46, XX, inv (4)(p13q13) [13]/46, XX [26]). The prognostic significance of this chromosomal abnormality is unknown.

Clonal heterogeneity as a driver of disease variability in the evolution of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal hematological diseases in which cells of the myelo-erythroid lineage are overproduced and patients are predisposed to leukemic transformation. Hematopoietic stem cells are the suspected disease-initiating cells, and these cells must acquire a clonal advantage relative to nonmutant hematopoietic stem cells to perpetuate disease. In 2005, several groups identified a single gain-of-function point mutation in JAK2 that associated with the majority of MPNs, and subsequent studies have led to a comprehensive understanding of the mutational landscape in MPNs. However, confusion still exists as to how a single genetic aberration can be associated with multiple distinct disease entities. Many explanations have been proposed, including JAK2V617F homozygosity, individual patient heterogeneity, and the differential regulation of downstream JAK2 signaling pathways. Several groups have made knock-in mouse models expressing JAK2V617F and have observed divergent phenotypes, each recapitulating some aspects of disease. Intriguingly, most of these models do not observe a strong hematopoietic stem cell self-renewal advantage compared with wild-type littermate controls, raising the question of how a clonal advantage is established in patients with MPNs. This review summarizes the current molecular understanding of MPNs and the diversity of disease phenotypes and proposes that the increased proliferation induced by JAK2V617F applies a selection pressure on the mutant clone that results in highly diverse clonal evolution in individuals.

JAK2 and MPL protein levels determine TPO-induced megakaryocyte proliferation vs differentiation

Megakaryopoiesis is a 2-step differentiation process, regulated by thrombopoietin (TPO), on binding to its cognate receptor myeloproliferative leukemia (MPL). This receptor associates with intracytoplasmic tyrosine kinases, essentially janus kinase 2 (JAK2), which regulates MPL stability and cell-surface expression, and mediates TPO-induced signal transduction. We demonstrate that JAK2 and MPL mediate TPO-induced proliferation arrest and megakaryocytic differentiation of the human megakaryoblastic leukemia cell line UT7-MPL. A decrease in JAK2 or MPL protein expression, and JAK2 chemical inhibition, suppress this antiproliferative action of TPO. The expression of JAK2 and MPL, which progressively increases along normal human megakaryopoiesis, is decreased in platelets of patients diagnosed with JAK2- or MPL-mutated essential thrombocytemia and primary myelofibrosis, 2 myeloproliferative neoplasms in which megakaryocytes (MKs) proliferate excessively. Finally, low doses of JAK2 chemical inhibitors are shown to induce a paradoxical increase in MK production, both in vitro and in vivo. We propose that JAK2 and MPL expression levels regulate megakaryocytic proliferation vs differentiation in both normal and pathological conditions, and that JAK2 chemical inhibitors could promote a paradoxical thrombocytosis when used at suboptimal doses.

Target hematologic values in the management of essential thrombocythemia and polycythemia vera

Treatment of essential thrombocythemia (ET) and polycythemia vera (PV) is aimed at preventing vascular complications, which are the main cause of morbidity and mortality in these diseases. Over the years, clinical trials have demonstrated that the incidence of thrombosis and bleeding can be reduced by controlling the blood cell counts, but the target hematological levels have varied across the studies. In this article, we review the evidence supporting the use of predefined target hematologic values for the management of ET and PV in routine clinical practice. At present, the recommended target hematocrit in PV is below 45%, regardless of the patients' risk profile. Concerning platelet counts, no direct correlation has been demonstrated with thrombotic risk in either ET or PV. Thus, although cytoreductive treatment reduces the rate of vascular complications in high-risk patients, no particular threshold of the platelet counts has been shown to be more protective against thrombosis. Extreme thrombocytosis is a risk factor for bleeding, particularly when aspirin or anagrelide are given. Leukocytosis at baseline or during follow-up appears to be a risk factor for thrombosis, mostly in high-risk patients. However, the clinical benefit of strictly controlling this parameter is not yet established. Finally, standardized definitions of response to cytoreductive treatment in ET and PV have recently been published. Nevertheless, they have been produced to compare the efficacy of new therapies in clinical trials, whereas its relevance in clinical practice has been questioned in retrospective studies showing that such response definitions do not correlate with the patients' clinical outcome.

Molecular classification of myeloproliferative neoplasms-pros and cons

Dameshek first postulated a common myeloproliferative heritage for the myeloproliferative disorders, now termed neoplasms. This prescient observation was validated by the description of a common mutation in exon 14 of JAK2 for patients with essential thrombocythemia, polycythemia vera and primary myelofibrosis. In recent years, our knowledge of the molecular abnormalities underpinning these disorders has expanded significantly. At the same time, we have continued to use a classification based largely upon the first clinical descriptions of these entities, which sometimes proves problematic in differentiating between these conditions and normal reactive processes, myelodysplasia and between the myeloproliferative neoplasm entities themselves. Here, we discuss the pros and cons of a molecular classification and its potential utility in diagnosis, prognosis, and therapeutics.

Cardiac hypertrophy associated with myeloproliferative neoplasms in JAK2V617F transgenic mice

BACKGROUND

Myeloproliferative neoplasms (MPNs) are blood malignancies manifested in increased production of red blood cells, white blood cells, and/or platelets. A major molecular lesion associated with the diseases is JAK2V617F, an activation mutation form of tyrosine kinase JAK2. Cardiovascular events represent the leading cause of morbidity and mortality associated MPNs, but the underlying mechanism is not well understood.

METHODS

Previously, we generated JAK2V617F transgenic mice which displayed MPN-like phenotypes. In the present study, we further characterized these mice by analyzing the time course of MPN phenotype development and associated cardiac abnormalities. We performed detailed histochemical staining of cardiac sections.

RESULTS

JAK2V617F transgenic mice developed cardiomegaly as a subsequent event of increased blood cell production during the course of MPN phenotype development. The cardiomegaly is manifested in increased ventricular wall thickness and enlarged cardiomyocytes. Trichrome and reticulin staining revealed extensive collagen fibrosis in the heart of JAK2V617F transgenic mice. Thrombosis in the coronary artery and inflammatory cell infiltration into cardiac muscle were also observed in JAK2V617F transgenic mice, and the latter event was accompanied by fibrosis.

CONCLUSION

JAK2V617F-induced blood disorders have a major impact on heart function and lead to cardiac hypertrophy. JAK2V617F transgenic mice represent an excellent model system to study both hematological malignancies and cardiovascular diseases.

Interferon and the treatment of polycythemia vera, essential thrombocythemia and myelofibrosis

Recombinant IFN-α (rIFN-α) induces complete hematologic remissions in patients with myeloproliferative neoplasms (MPNs), but its use has been limited by side effects owing to the relatively high doses used. Now, low-dose rIFN-α is stressed, starting relatively early in the course of the MPNs. In polycythemia vera, this has resulted in a significant clinical, hematologic, morphologic and molecular response manifested by reduction in the JAK2(V617F) allele burden, sustained even after discontinuation of recombinant IFN. In essential thrombocythemia, platelet count reduction is prompt and durable without treatment for varying periods. In hypercellular primary myelofibrosis, rIFN-α has restored normal blood counts, reduced splenomegaly and induced morphologic marrow remissions. This article highlights our current use of rIFN-α in MPNs.

The therapeutic goals of essential thrombocythemia under the clouds of over-treatment and under-treatment

INTRODUCTION

Therapeutic stratification after the accurate essential thrombocythemia (ET) diagnosis is made based on the medical history (age, previous thrombosis), clinical assessments (cardiovascular [CV] risk factors, comorbidities, systemic diseases), laboratory examinations (leukocytosis, extreme thrombocytosis, anemia) and if available further sophistical analyses (CD34 count, JAK2V617F homozygosity, and mutant allele burden).

AREAS COVERED

Current conventional therapeutic tools for reaching those goals are observation, low-dose aspirin, hydroxyurea, anegrelide and interferon alpha. Those treatment modalities are used alone or in combination to get the therapeutic goals in ET patients. The ET literature search was made in PubMed with particular focus on the clinical trials, recommendations, guidelines and expert opinions.

EXPERT OPINION

The most important step for the therapeutic decision of ET in the clinic is the risk assessments. Clinical decision making starts with the detection of the age and the prior thrombosis history of the ET patient. Treatment goals in ET are to avoid thrombosis and bleeding, to treat ET-related symptoms, improve quality of life and to minimize risk of malignant transformation and/or post-ET myelofibrosis.

MPL Baltimore mutation and thrombocytosis: case report and literature review

Thrombocytosis is a common finding and is a frequent cause of referral for further investigation. The MPL Baltimore (Lys39Asn) mutation has been reported as a cause of thrombocytosis in 7% of African Americans. We describe an 11-month-old Ethiopian Jewish boy referred for evaluation of thrombocytosis who was found to be homozygous for MPL Baltimore. So far, there is no indication whether patients with thrombocytosis who have this mutation, particularly homozygotes, are at increased risk of thrombotic or hemorrhagic complications. Nevertheless, this entity should be considered in the differential diagnosis of every patient with thrombocytosis, particularly those of African origin.

Problems and pitfalls regarding WHO-defined diagnosis of early/prefibrotic primary myelofibrosis versus essential thrombocythemia

Reproducibility and clinical usefulness of the WHO classification of chronic myeloproliferative neoplasm (MPN) persist to be a controversial issue. Major arguments are focused on the critical impact of histopathology, particularly concerning the distinction between essential thrombocythemia (ET) versus early/prefibrotic primary myelofibrosis (PMF). Regarding bone marrow morphology, WHO guidelines strictly require the recognition of characteristic histological patterns based on standardized features and a consensus of clinical and molecular-genetic data. Molecular-genetic findings as JAK2V617F, may aid to exclude reactive thrombocytosis, although in ET and PMF only 50-60% of the cases show these aberrations. Considerable doubts over the existence of early/prefibrotic PMF have been expressed with the consequence to include this entity in the ET category. On the other hand, it has to be argued that some of the critical studies failed to adhere very strictly to the WHO guidelines. Contrasting this situation, recently published retrospective and prospective clinico-pathological studies featuring the WHO criteria provided an important information on disease outcomes supporting the existence of early/prefibrotic PMF as a distinct clinico-pathologic entity in patients presenting clinically with ET. Therefore, this controversy suggests a scientific project, including the community of pathologists and hematologists, for providing sound, objective and reproducible criteria for diagnosing early/prefibrotic PMF.

Does thrombocyte size give us an idea about thrombocytosis etiology?

In the presence of a pathogenetic mutation in JAK2 or MPL, a differential diagnosis of essential thrombocythemia (ET) from reactive causes is relatively simple. However, in patients with suspected ET who lack JAK2 and MPL mutations, the exclusion of secondary causes is especially important. The study was aimed to explore the clinical application of particularly mean platelet volume (MPV), hemoglobin, red blood cell indices, white blood cell, serum iron profile, and C-reactive protein level in the differential diagnosis of thrombocytosis. Medical records of 49 patients, consisting of reactive thrombocytosis (RT) and ET were retrospectively reviewed. The mean MPV level in RT group was 7.49 fL, and in ET group was 8.80 fL (P < 0.01). A cutoff point of <8.33 fL was found to have significant predictive value according to ROC curve analysis. This cutoff was associated with 83% positive predictive value (PPV) and 74% negative predictive value (NPV) in the diagnosis of ET and had a sensitivity of 65% and specificity of 89% for ET. Investigation of MPV is cheap, quick, and noninvasive, and may serve as a predictor of primary thrombocytosis. High sensitivity, specificity, PPV, and NPV enable this test an important tool and a possible surrogate marker in clinical practice.