Essential thrombocythaemia: challenges and evidence-based management

What factors determine the pregnancy outcome in patients with essential thrombocythemia?

Objectives: Treatment of essential thrombocythemia (ET) is particularly challenging in pregnancy due to the increased risk of thromboembolic complications. Therefore, the use of antithrombotic regimens are recommended in pregnant women with ET.Methods: The study included 52 pregnancies in 27 patients diagnosed with ET, who were treated in Department of Haematology. The influence of anticoagulant, antiplatelet and cytoreductive therapy on the course and outcome of pregnancy was analysed. This study also examined if there was any correlation between molecular and clinical features such as mutational profile, blood count, presence of acquired von Willebrand syndrome (AvWS), the International Prognostic Score for Essential Thrombocythemia (IPSET) risk group and the IPSET-thrombosis risk group and pregnancy outcome.Results: Study participants who received antithrombotic therapy were significantly more likely to give birth to a healthy child. The best outcomes were observed in patients who received low dose acetylsalicylic acid (ASA) together with low-molecular-weight heparin (LMWH). There was a statistically significant correlation between classification to the high-risk group according to the IPSET-thrombosis score and incidence of miscarriage. Cytoreductive treatment with interferon-α2, as well as the presence of AvWS did not increase the likelihood of pregnancy loss. Blood counts and presence of specific gene mutations profile were also not found to be significant determinants of pregnancy outcome.Conclusion: To our best knowledge, this is the first clinical study investigating the correlation between risk group (according to IPSET and IPSET-thrombosis) and pregnancy outcome in women with ET.

Clinical and Prognostic Features of Essential Thrombocythemia: Comparison of 2001 WHO Versus 2008/2016 WHO Criteria in a Large Single-center Cohort

BACKGROUND

According to 2008/2016 classification of the World Health Organization (WHO), a platelet (PLT) count ≥ 450 × 10⁹/L, reduced from the previously published WHO 2001 indicated level ≥ 600 × 10⁹/L, was considered the new PLT threshold for the diagnosis of essential thrombocythemia (ET).

PATIENTS AND METHODS

To validate this important diagnostic change in a setting of current clinical practice, we retrospectively analyzed clinical and hematologic features at diagnosis and during follow-up of 162 patients with ET, diagnosed in our center from January 2008 to December 2017. We subdivided patients according to PLT value at baseline into Group A (PLT ≥ 600 × 10⁹/L) (124 patients; 76.5%) and Group B (PLT ≥ 450 × 10⁹/L < 600 × 10⁹/L) (38 patients; 23.5%).

RESULTS

Among clinical features, only the median value of leukocytes (P < .001) was significantly higher in Group A. Cytostatic treatment was administered in 103 patients, with a significantly higher rate in patients of group A (P < .001). After a median follow-up of 42.4 months (interquartile range, 22.1-70.6 months), 8 thrombotic events were recorded in the entire cohort, without differences between the 2 groups (P = .336). The 5-year overall survival (OS) of the entire cohort was 96.9% (95% confidence interval, 92.6%-100%), without differences between the 2 groups (P = .255).

CONCLUSIONS

Our data indicate a substantial homogeneity among patients with ET regardless of the PLT count at diagnosis, thus confirming the usefulness of the 2008/2016 WHO diagnostic criteria.

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.

Portal vein thrombosis in a child with essential thrombocythemia seven years after diagnosis

Portal vein thrombosis in children with essential thrombocythemia (ET) is a rarity. Here, we describe the long-term follow up of our previously reported case that since has developed portal vein thrombosis (PVT) 7-years after diagnosis. Our patient had presented with PVT with normal platelet counts and massive asymptomatic splenomegaly. Ultrasound and Computerized tomography confirmed presence of PVT. Our case highlights the importance of long-term follow up of children with ET for thrombosis, especially PVT, as it can happen without symptoms and normal platelet counts.

Essential Thrombocytosis and Labor Epidural Placement While on Aspirin: Assessing Hemorrhagic Risks: A Case Report

Essential thrombocytosis (ET) is a rare disease with known thrombotic and bleeding complications. We encountered a patient with a diagnosis of longstanding Janus kinase-2 gene-negative ET on aspirin therapy presenting for labor epidural. Evaluation of platelet function with point-of-care analysis using Plateletworks in a community hospital setting allowed confirmation of adequate numbers of functional platelets to support safe epidural placement. The relevant issues of ET for anesthesia management with labor epidurals are discussed. Unique, relevant, and unexpected findings from the platelet function testing are presented.

Off-pump myocardial revascularization in a high-risk patient with essential thrombocythemia

Essential thrombocythemia is a rare type of myeloproliferative disorder. Cerebral, myocardial, and peripheral thrombosis are all frequent complications of the disease. A 71-year-old man presented with severe coronary artery disease, associated with cerebral vascular ischemic changes and erythromelalgia. His platelet count was 1,486 ×10(3)/μL. The patient underwent successful myocardial revascularization by means of an off-pump technique after his platelet count had been reduced by hydroxycarbamide administration. We conclude that the use of off-pump cardiopulmonary bypass in high-risk patients with essential thrombocythemia is safe. Reducing platelet count via the administration of hydroxycarbamide and the careful balancing of antiplatelets and anticoagulants is crucial in determining the outcome of surgery.

Successful management of acute bleeding in essential thrombocythemia using automated cell separator

This case represents the challenging role of automated cell separators in management of acute hemorrhagic crisis in a young female patient of essential thrombocythemia. A 17 year old girl having body weight of 41 kg presented to us with profuse nasal bleed. Complete blood counts revealed extremely high platelet counts of 2987×10(9)/l. Due to no response by oral hydroxyurea for last 2 months, urgent mechanical platelet reduction was planned to prevent further complication. A rebound phenomenon of increase in circulating platelet count was observed after every therapeutic platelet reduction. Seven procedures had to be performed on alternate days to bring down the platelet counts to less than 600×10(9)/l. Patient was maintained on oral anagrelide therapy and discharged in a stable condition after 14 days. Therapeutic platelet reduction causes rapid platelet reduction and helps in managing acute complications.

Acquired hemophilia A in a patient with essential thrombocythemia

A 69-year-old woman with essential thrombocythemia (ET) developed giant ecchymosis, and she was admitted to hospital. Marked anemia (Hb 8.1 g/dl) accompanied by a prolonged activated partial thromboplastin time (89.6 s) was observed, and she received red blood cells (RBC) and fresh frozen plasma (FFP). On day 2 after admission, consciousness disturbance suddenly occurred, whereas computed tomography of the brain showed no evidence of bleeding. As the ecchymosis progressed, she developed shock. Although RBC and FFP transfusions were administered, she developed multi-organ failure and died 48 h after admission. Low factor VIII activity (<1%) accompanied by factor VIII inhibitor (17 Bethesda units) was found after her death. An autopsy revealed cerebral infarction without cerebral herniation. To date, acquired hemophilia A accompanying ET has been described in only one other patient. Although acquired factor VIII inhibitor is a rare disease, it should be tested for in ET patients with marked hemorrhagic tendency.

Preoperative evaluation of the oncology patient

This review focuses on the unique perioperative concerns of patients with cancer undergoing surgery. Importantly, not all surgical procedures are intended as cures: some patients who have cancer also undergo surgery for noncancer issues. Also, many of these patients have undergone prior chemotherapy and/or radiation therapy that can introduce perioperative concerns. These previous treatments, unique to patients with cancer, can adversely affect their cardiovascular, pulmonary, gastrointestinal, renal, and endocrine systems. This article also summarizes many important effects of a wide variety of chemotherapy agents in use today.

Impact of leukocytosis on thrombotic risk and survival in 532 patients with essential thrombocythemia: a retrospective study

Established risk factors for thrombosis in essential thrombocythemia (ET) include age (≥ 60 years) and previous vascular events. Recently, also leukocytosis has been proposed in risk stratification of ET patients. We report a retrospective study on 532 ET patients followed for a median of 7.6 years. Sixty-four patients (12%) developed 95 thrombotic events during follow-up. Together with the high-risk condition, a white blood cell (WBC) value above 11 × 10⁹/L, corresponding to the fourth percentile value, significantly correlated with a higher thrombotic risk (p = 0.033) by Cox proportional hazards. Moreover, the cumulative risk of thrombosis was significantly higher in high-risk patients with WBC >11 × 10⁹/L. JAK2 V617F mutation did not correlate with thrombosis. Overall, 123 (23%) patients died. Three independent parameters were noted as prognostic factors for survival in multivariate analysis: age > 60 years, leukocytosis >11 × 10⁹/L, and hemoglobin level below normal values. Based on these parameters, three groups of risk were defined, with significantly different survivals. Baseline leukocytosis correlated with a higher thrombotic risk in high-risk patients and identified a cohort of patients with worse survival.

Preoperative evaluation of the oncology patient

This review focuses on the unique perioperative concerns of patients with cancer undergoing surgery. Importantly, not all surgical procedures are intended as cures: some patients who have cancer also undergo surgery for noncancer issues. Also, many of these patients have undergone prior chemotherapy and/or radiation therapy that can introduce perioperative concerns. These previous treatments, unique to patients with cancer, can adversely affect their cardiovascular, pulmonary, gastrointestinal, renal, and endocrine systems. This article also summarizes many important effects of a wide variety of chemotherapy agents in use today.

Preoperative evaluation of the oncology patient

This article focuses on the unique perioperative concerns of patients with cancer undergoing surgery. Importantly, not all surgical procedures are intended as cures; cancer patients also undergo surgery for noncancer issues. Many of these patients have undergone prior chemotherapy or radiation therapy that can introduce perioperative concerns. These prior treatments, unique to cancer patients, can affect their cardiovascular, pulmonary, gastrointestinal, renal, and endocrine systems adversely, and this article summarizes many important effects of various chemotherapy agents in use today.

A latent form of essential thrombocythemia presenting as portal cavernoma

Essential thrombocythemia is frequently associated with abdominal thrombotic complications including portal cavernoma as a consequence of chronic portal vein thrombosis. Essential thrombocythemia in a latent form is difficult to identify at onset due to the absence of an overt disease phenotype. In the presented case report, the diagnosis of essential thrombocythemia was initially missed because the typical disease phenotype was masked by bleeding and hypersplenism. The correct diagnosis was only reached when the patient experienced persistent thrombocytosis and pseudohyperkalemia after a shunt operation.

Essential thrombocythemia: past and present

Essential thrombocythemia (ET) is a clonal myeloproliferative disorder characterized by sustained increase in platelet number and tendency for thromboembolism. A somatic point mutation that causes a constitutive activation of the JAK2 gene is found in one in two ET patients. ET is more common in women, its incidence being 0.6-2.5/100,000 patient/year and the median age at diagnosis is 65-70 years. ET can affect all age groups, including children (0.09 cases/year), and is often diagnosed in the third-fourth decade of life. Rare cases of familial ET have been reported. Miscarriages are 3-4 times more common among women with ET than in the general population, especially in patients carrying JAK2V617F. Microvascular disturbances are typical of ET, but a major thrombosis (2/3 arterial and 1/3 venous; 1, 2-3% patient/year) is the main cause of morbidity and mortality. Age over 60 years and/or previous thrombosis are validated risk factor for thrombosis. Hemorrhages occur in 0.33% patient/year, mainly in those with a platelet count over 1,500 x 10(9)/L. Progression to myelofibrosis and leukemia is more common in patients carrying the JAK2V617F mutation, and is estimated to occur in 0.16% and 0.12% patient/year, respectively. The ET-related mortality ratio with respect to the general population is 1:1, while for polycythemia vera it is 1.6:1. Low-dose aspirin is useful for microvascular disturbances, and in the primary and secondary prevention of major thrombosis in high-risk patients, but it is not recommended in patients with a platelet count over 1,500 x 10(9)/L. Hydroxyurea is used as first-line treatment in high-risk patients. Other drugs available are alpha-interferon, anagrelide, pipobroman and busulphan.

Pericardial Hemorrhage Due to Acetylsalicylic Acid in a Patient With Essential Thrombocythemia

Essential thrombocythemia is a clonal myeloproliferative disorder that causes thrombocytosis. Essential thrombocythemia is characterized by increased incidence of thrombosis with arterial event more than venous events and hemorrhagic complications. Acetylsalicylic acid enhances both minor and major bleedings. The authors describe pericardial hemorrhage, which is related to the use of low-dose acetylsalicylic acid in a patient with essential thrombocythemia. The patient was successfully managed with clopidogrel therapy during the 16 months follow-up without recurrent thrombotic or hemorrhagic events.

JAK2 V617F in myeloid disorders: What do we know now, and where are we headed?

Activating tyrosine kinase (TK) mutations disrupt cellular proliferation and survival pathways and are increasingly recognized as a fundamental cause of human cancers. Until very recently, the only TK mutations widely observed in myeloid neoplasia were the BCR/ABL1 fusions characteristic of chronic myeloid leukemia and some acute leukemias, and FLT3 activating mutations in a minority of acute myeloid leukemias. Several rare TK mutations are found in various atypical myeloproliferative disorders, but big pieces of the pathobiological puzzle were glaringly missing. In the first half of 2005, one gap was filled in: 7 studies identified the same acquired amino acid substitution (V617F) in the Janus kinase 2 (JAK2) TK in large numbers of patients with diverse clonal myeloid disorders. Most affected patients suffer from the classic BCR/ABL1-negative myeloproliferative disorders (MPD), especially polycythemia vera (74% of n = 506), but a subset of people with essential thrombocythemia (36% of n = 339) or myelofibrosis with myeloid metaplasia (44% of n = 127) bear the identical mutation, as do a few individuals with myelodysplastic syndromes or an atypical myeloid disorder (7% of n = 556). This long-sought common mutation in BCR/ABL1-negative MPD raises many provocative biological and clinical questions, and demands re-evaluation of prevailing diagnostic algorithms for erythrocytosis and thrombocytosis. JAK2 V617F may provide novel molecular targets for drug therapy, and suggests other places to seek cooperating mutations or mutations associated with similar phenotypes. The story of this exciting finding will unfold rapidly in the years ahead, and ongoing developments will be important for all hematologists to understand.

JAK2 V617F mutation in essential thrombocythemia: correlation with clinical characteristics, response to therapy and long-term outcome in a cohort of 275 patients

The JAK2(V617F) mutation occurs in 50% of patients with essential thrombocythemia (ET). We investigated the correlation between the JAK2(V617F) mutation and clinical and laboratory characteristics, thrombohemorrhagic risk and incidence of disease evolution in 275 patients with ET followed for a median follow-up of 7 years. JAK2(V617F) mutation was detected in 175 patients (64%), of whom 173 were heterozygous. Patients with the mutation were older and displayed higher hemoglobin and hematocrit levels, but lower platelet count. Cytotoxic treatment requirement was similar in the two groups, but patients with the mutation showed better responses. Incidence of thrombosis and disease evolution was comparable. JAK2 mutational status assessment was valuable to distinguish two populations of patients with ET, showing distinctive hematologic and clinical features.

Thrombocytosis and leukocytosis interaction in vascular complications of essential thrombocythemia

To elucidate the role of thrombocytosis, alone or in combination with standard (age, previous cardiovascular events) and novel (leukocytosis, JAK2(V617F) mutational status) risk factors, in the cardiovascular events of essential thrombocythemia (ET), we analyzed a cohort of 1063 patients. We found that a platelet count at diagnosis greater than 1000 x 10(9)/L was associated with significantly lower rate of thrombosis in multivariable analysis and, if combined with leukocytes less than 11 x 10(9)/L, pointed to a "low-risk" category with a rate of thrombosis of 1.59% of patients/year. On the contrary, the highest risk category (thrombosis rate, 2.95% of patients/year) was constituted of patients with leukocytosis, lower platelet count, and a JAK2(V617F) mutated genotype in most cases (77% vs 26% in the low-risk group), independently from standard risk factors. These data challenge the theory that elevated platelet count increases thrombosis risk in ET and suggest prospective clinical trials to support this hypothesis.

Myeloproliferative disorder as the cause of peripheral ischemia in a young patient

A 35-year-old patient with rest pain and peripheral gangrene was referred with a diagnosis of Takayasu's disease but had myeloproliferative disorder (primary thrombocythemia). The angiogram revealed surgically noncorrectable small vessel occlusive disease with no evidence of atheroma. Medical therapy with cytotoxic and antiplatelet agents achieved satisfactory results with excellent wound healing after surgical amputation of necrotic tissue. The need for early diagnosis of this condition is emphasized.

Pulmonary hypertension in patients with essential thrombocythemia and reactive thrombocytosis

Increased incidence of pulmonary hypertension (PH) has been reported in patients with chronic myeloproliferative disorders. The exact incidence of PH in essential thrombocythemia (ET) is unknown. Most of the reported literature consists of case reports or small studies. We designed this study to asses the incidence of PH in patients with ET and reactive thrombocytosis. Previously or newly diagnosed 46 patients with ET, and 40 patients with reactive thrombocytosis secondary to iron deficiency anemia were found to be eligible for this study. Diagnosis of PH was established via transthoracic echocardiography. PH was found in 22 (47.8%) out of 46 patients with ET. Seven patients with PH were newly diagnosed ET, 5 patients with PH were in low, and the other patients with PH were in intermediate or high risk category. We found statistically significant difference in terms of platelet counts between ET patients with PH and without PH (p = 0.027). None of the patients with reactive thrombocytosis had PH. In conclusion, PH appears to be common in patients with ET. Therefore, all patients with ET should be evaluated for PH. Larger and prospective studies are required to clarify the long-term impact of PH on the survival of these patients. Future studies are also needed to determine whether cytoreductive treatment and aspirin prevent the development of PH, and to determine the effects of cytoreductive treatments and aspirin on the prognosis of PH. The effect of PH on ET prognosis should also be determined in low risk ET patients.

Analysis of risk factors predicting thrombotic and/or haemorrhagic complications in 306 patients with essential thrombocythemia

Thrombotic and haemorrhagic complications are the main causes of morbidity in Essential Thrombocythemia (ET). We investigated the clinical and laboratory characteristics associated with the occurrence of these events with the aim of identifying subgroups of patients who might benefit from anti-aggregant and/or cytoreductive therapy. The study involved 306 consecutive ET patients (median age 58 years and median follow-up 96 months); the investigated variables were age, gender, platelet count, previous history of thrombotic or haemorrhagic events, disease duration and cardiovascular risk factors. Forty-six patients (15%) experienced thrombotic complications during the follow-up: 26/64 patients with a previous history of thrombosis (40.6%) and 20/242 patients without (8.3%; p < 0.0001). Thirty-one patients (10%) experienced major haemorrhagic complications, mainly gastrointestinal tract bleeding: 3 with and 28 without a history of haemorrhagic events (p = 0.052). When the patients with a negative history of thrombosis were stratified on the basis of the number of cardiovascular risk factors (none vs. one vs. more than one), there was a significant correlation with the occurrence of thrombotic events (p < 0.05). ET patients with a positive history of thrombosis are at high risk of thrombotic complications, and should receive cytoreductive and anti-aggregant treatment. Asymptomatic patients with a negative thrombotic history and no cardiovascular risk factors are at low risk, and should not be treated. Patients with a negative thrombotic history and one or more cardiovascular risk factors are at intermediate risk, and should be treated with anti-aggregant and/or cytoreductive therapy. The need for treatment should be periodically re-evaluated. Age and platelet count, generally accepted as very important risk factors for thrombosis, did not seem in our series associated with an increased risk for thrombosis.

Postsurgery outcomes in patients with polycythemia vera and essential thrombocythemia: a retrospective survey

A multicenter retrospective analysis was performed to estimate the frequency of thrombosis and hemorrhage after surgical procedures in patients with polycythemia vera (PV) and patients with essential thrombocythemia (ET). Data from 105 patients with PV and 150 patients with ET were analyzed, for a total of 311 surgical interventions. An emergency procedure was performed in 25 (8.1%) patients; 194 surgeries were done under general anesthesia, and 21 (23%) of 91 abdominal interventions were done under laparoscopy; 155 (50.1%) were major surgeries. Subcutaneous heparin was administered in 169 (54.3%) of 311 cases and antiplatelet therapy in 48 (15.4%) of 311 case interventions. One hundred eighty-eight (74%) of 255 patients were on cytoreductive therapy before surgery. No events were observed in 259 (83.2%) of 311 procedures during 3 months of follow-up; there were 12 arterial and 12 venous thrombotic events, 23 major and 7 minor hemorrhages, and 5 deaths. Arterial thromboses were more frequent in ET (5.3% vs 1.5%; P=.08), venous events were more frequent in PV (7.7% vs 1.1%; P=.002). There was not a correlation between bleeding episodes and the type of diagnosis, use of antithrombotic prophylaxis, or type of surgery. A high proportion of PV and ET surgeries was complicated by vascular occlusion (7.7%) or by a major hemorrhage (7.3%). Prospective investigations analyzing the optimal prophylaxis in these patients are suggested.

Classification of Ph-Negative Chronic Myeloproliferative Disorders – Morphology as the Yardstick of Classification

OBJECTIVE

Histopathology of bone marrow (BM) biopsies plays a crucial role in the interdisciplinary approach to diagnosis and classification of Ph-negative chronic myeloproliferative disorders. Based on careful clinicopathologic studies, BM features are critical determinants that help to predict overall prognosis, to detect complications such as progression to myelofibrosis and blast crisis, and to assess therapy-related changes.

METHODS AND RESULTS

A systematic evaluation of BM histopathology allows an objective identification of cases of (true) essential thrombocythemia and their separation from early prefibrotic stages of chronic idiopathic myelofibrosis. By follow-up examinations that include BM biopsies, the progression of the disease process is unveiled, which is especially important for patients with initial polycythemia vera and prefibrotic chronic idiopathic myelofibrosis that may require a different therapeutic approach than the full-blown stages.

CONCLUSION

BM biopsy should be considered as major diagnostic tool for evaluation and follow-up of patients enrolled in prospective studies.

Polycythaemia vera and essential thrombocythaemia: current treatment strategies

Polycythaemia vera (PV) and essential thrombocythaemia (ET) are classified as Philadelphia-negative chronic myeloproliferative diseases. Both PV and ET are rare diseases, but the prevalence is high. Patients who have not been treated for the diseases are at great risk of morbidity and mortality as a result of thrombohaemorrhagic events. However, if patients have been well treated, their prognosis is good and life-expectancy approaches normal. This article provides diagnostic tools and flowcharts for treatment of PV and ET. Treatment of PV and ET should be risk-adjusted and individualised. Low-dose aspirin is recommended as an antiaggregative drug in both diseases. For PV, phlebotomy to control a haematocrit at <0.45 is the cornerstone in treatment, and treatment with hydroxycarbamide (hydroxyurea) or interferon (IFN)-alpha is added to reduce hypermetabolic symptoms or splenomegaly becoming cytoreductive. In ET, hydroxycarbamide and anagrelide are the most used drugs, and anagrelide may also be added in PV to reduce thrombocytosis. IFNalpha is the only myelosuppressive treatment available during pregnancy. Current controversies regarding treatment illustrate the need for more randomised clinical trials. Demonstration of over expression of the PV-1 gene and in particular the JAK-2 mutation will be novel diagnostic criteria and may have an impact for future therapy of both PV and ET.

Essential thrombocythemia

Essential thrombocythemia (ET) is an acquired myeloproliferative disorder (MPD) characterized by a sustained elevation of platelet number with a tendency for thrombosis and hemorrhage. The prevalence in the general population is approximately 30/100,000. The median age at diagnosis is 65 to 70 years, but the disease may occur at any age. The female to male ratio is about 2:1. The clinical picture is dominated by a predisposition to vascular occlusive events (involving the cerebrovascular, coronary and peripheral circulation) and hemorrhages. Some patients with ET are asymptomatic, others may experience vasomotor (headaches, visual disturbances, lightheadedness, atypical chest pain, distal paresthesias, erythromelalgia), thrombotic, or hemorrhagic disturbances. Arterial and venous thromboses, as well as platelet-mediated transient occlusions of the microcirculation and bleeding, represent the main risks for ET patients. Thromboses of large arteries represent a major cause of mortality associated with ET or can induce severe neurological, cardiac or peripheral artery manifestations. Acute leukemia or myelodysplasia represent only rare and frequently later-onset events. The molecular pathogenesis of ET, which leads to the overproduction of mature blood cells, is similar to that found in other clonal MPDs such as chronic myeloid leukemia, polycythemia vera and myelofibrosis with myeloid metaplasia of the spleen. Polycythemia vera, myelofibrosis with myeloid metaplasia of the spleen and ET are generally associated under the common denomination of Philadelphia (Ph)-negative MPDs. Despite the recent identification of the JAK2 V617F mutation in a subset of patients with Ph-negative MPDs, the detailed pathogenetic mechanism is still a matter of discussion. Therapeutic interventions in ET are limited to decisions concerning the introduction of anti-aggregation therapy and/or starting platelet cytoreduction. The therapeutic value of hydroxycarbamide and aspirin in high risk patients has been supported by controlled studies. Avoiding thromboreduction or opting for anagrelide to postpone the long-term side effects of hydrocarbamide in young or low risk patients represent alternative options. Life expectancy is almost normal and similar to that of a healthy population matched by age and sex.

Risk stratification for survival and leukemic transformation in essential thrombocythemia: a single institutional study of 605 patients

Unlike the case with thrombosis, prognostic models for survival and leukemic transformation (LT) in essential thrombocythemia (ET) are not available. Among 605 patients with ET seen at our institution and followed for a median of 84 months, 155 died and LT was documented in 20 patients (3.3%). In a multivariable analysis, hemoglobin level below normal (females<120 g/l; males<135 g/l) was identified as an independent risk factor for both inferior survival and LT. Additional risk factors for survival included age > or =60 years, leukocyte count> or =15 x 10(9)/l, smoking, diabetes mellitus and thrombosis. For LT, platelet count> or =1000 x 10(9)/l but not cytoreductive therapy was flagged as an additional independent risk factor. In fact, four of the 20 patients (20%) with LT were untreated previously. We used the above information to construct prognostic models that effectively discriminated among low-, intermediate- and high-risk groups with respective median survivals of 278, 200 and 111 months (P<0.0001), and LT rates of 0.4, 4.8 and 6.5% (P=0.0009) respectively. Presence of JAK2V617F did not impact either survival or LT and mutational frequency was similar among the different risk groups.

Megakaryocyte development and platelet production

Megakaryocytopoiesis involves the commitment of haematopoietic stem cells, and the proliferation, maturation and terminal differentiation of the megakaryocytic progenitors. Circulating levels of thrombopoietin (TPO), the primary growth-factor for the megakaryocyte (MK) lineage, induce concentration-dependent proliferation and maturation of MK progenitors by binding to the c-Mpl receptor and signalling induction. Decreased platelet turnover rates results in increased concentration of free TPO, enabling the compensatory response of marrow MKs to increased platelet production. C-Mpl activity is orchestrated by a complex cascade of signalling molecules that induces the action of specific transcription factors to drive MK proliferation and maturation. Mature MKs form proplatelet projections that are fragmented into circulating particles. Newly developed thrombopoietic agents operating via c-Mpl receptor may prove useful in supporting platelet production in thrombocytopenic state. Herein, we review the regulation of megakaryocytopoiesis and platelet production in normal and disease state, and the new approaches to thrombopoietic therapy.

JAK2 V617F is a rare finding in de novo acute myeloid leukemia, but STAT3 activation is common and remains unexplained

Signal transducer and activator of transcription (STAT) proteins are phosphorylated and activated by Janus kinases (JAKs). Recently, several groups identified a recurrent somatic point mutation constitutively activating the hematopoietic growth factor receptor-associated JAK2 tyrosine kinase in diverse chronic myeloid disorders - most commonly classic myeloproliferative disorders (MPD), especially polycythemia vera. We hypothesized that the JAK2 V617F mutation might also be present in samples from patients with acute myeloid leukemia (AML), especially erythroleukemia (AML-M6) or megakaryoblastic leukemia (AML-M7), where it might mimic erythropoietin or thrombopoietin signaling. First, we documented STAT3 activation by immunoblotting in AML-M6 and other AML subtypes. Immunoperoxidase staining confirmed phosphorylated STAT3 in malignant myeloblasts (21% of cases, including all AML-M3 samples tested). We then analyzed genomic DNA from 162 AML, 30 B-cell lymphoma, and 10 chronic lymphocytic leukemia (CLL) samples for JAK2 mutations, and assayed a subset for SOCS1 and FLT3 mutations. Janus kinase2 V617F was present in 13/162 AML samples (8%): 10/13 transformed MPD, and three apparent de novo AML (one of 12 AML-M6, one of 24 AML-M7, and one AML-M2 - all mixed clonality). FLT3 mutations were present in 5/32 (16%), while SOCS1 mutations were totally absent. Lymphoproliferative disorder samples were both JAK2 and SOCS1 wild type. Thus, while JAK2 V617F is uncommon in de novo AML and probably does not occur in lymphoid malignancy, unexplained STAT3 activation is common in AML. Janus kinase2 extrinsic regulators and other proteins in the JAK-STAT pathway should be interrogated to explain frequent STAT activation in AML.

JAK2 V617F in myeloid disorders: molecular diagnostic techniques and their clinical utility: a paper from the 2005 William Beaumont Hospital Symposium on Molecular Pathology

In early 2005, several groups of investigators studying myeloid malignancies described a novel somatic point mutation (V617F) in the conserved autoinhibitory pseudokinase domain of the Janus kinase 2 (JAK2) protein, which plays an important role in normal hematopoietic growth factor signaling. The V617F mutation is present in blood and marrow from a large proportion of patients with classic BCR/ABL-negative chronic myeloproliferative disorders and of a few patients with other clonal hematological diseases such as myelodysplastic syndrome, atypical myeloproliferative disorders, and acute myeloid leukemia. The JAK2 V617F mutation causes constitutive activation of the kinase, with deregulated intracellular signaling that mimics continuous hematopoietic growth factor stimulation. Within 7 months of the first electronic publication describing this new mutation, clinical molecular diagnostic laboratories in the United States and Europe began offering JAK2 mutation testing on a fee-for-service basis. Here, I review the various techniques used by research groups and clinical laboratories to detect the genetic mutation underlying JAK2 V617F, including fluorescent dye chemistry sequencing, allele-specific polymerase chain reaction (PCR), real-time PCR, DNA-melting curve analysis, pyrosequencing, and others. I also discuss diagnostic sensitivity, performance, and other practical concerns relevant to the clinical laboratorian in addition to the potential diagnostic utility of JAK2 mutation tests.

Essential thrombocythemia: a review of diagnostic and pathologic features

CONTEXT

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder (CMPD) characterized predominately by thrombocytosis and abnormal megakaryocyte proliferation. The current diagnostic criteria require a combination of clinical, histologic, and cytogenetic data. The diagnosis relies largely on exclusion of other causes of thrombocytosis.

OBJECTIVE

Describe historical, clinical, and laboratory features of ET in order to understand, clarify, and more accurately diagnose this entity.

DATA SOURCES

Review contemporary and historical literature on ET and other causes of thrombocytosis.

CONCLUSIONS

ET is a relatively indolent and often asymptomatic CMPD that is characterized primarily by a sustained elevation in platelets > or = 600 x 10(3)/microL (> or = 600 x 10(9)/L), proliferating enlarged and hyperlobated megakaryocytes, and minimal to absent bone marrow fibrosis. Significant changes and revisions to the diagnostic requirements and criteria for ET have occurred during the last 30 years. Recently, a mutation in the Janus kinase 2 (JAK2) gene has been found in a significant number of cases of ET and other CMPDs. In up to 57% of ET cases, a mutation in the JAK2 gene can be detected. In the absence of a JAK2 mutation and features of another CMPD, the diagnosis of ET remains a diagnosis of exclusion after other causes of thrombocytosis have been excluded.

A critical reappraisal of the WHO classification of the chronic myeloproliferative disorders

Following the introduction of the WHO classification of chronic myeloproliferative disorders (MPDs), after approximately 5 years, a critical reappraisal appears to be warranted. Retrospective clinico-pathological evaluations conducted in the meantime, as well as the detection of new biomarkers, may aid in testing the validity of these new criteria. Based on a large series of patients with chronic myeloid leukemia (CML), an analysis of bone marrow (BM) features and risk classifications revealed that the fiber content exerted a most important and independent impact on prognosis. This finding was also supported in a prospective randomized study and therefore myelofibrosis should be included in any staging system in CML related to survival. Moreover, it is important to emphasize the dynamics of the disease process in MPDs, especially in polycythemia vera (PV) and chronic idiopathic myelofibrosis (CIMF). Latent-stage PV is difficult to recognize when adhering to the proposed limits for hemoglobin (or red cell mass) without regarding the erythropoietin (EPO) level, endogenous erythroid colonies (EECs) or BM histopathology. Initial PV may firstly present with complications and, when accompanied by a high platelet count, mimics essential thrombocythemia (ET). Consequently, BM morphology and EPO level should be entered as major diagnostic criteria for PV. To document more accurately the progress of disease, a simplified scoring system concerning myelofibrosis has to be included in the histological description of CIMF. The diagnostic guidelines of BM features in ET should be improved because, usually, there is neither a significant proliferation nor left-shifting of the granulo- and erythropoiesis detectable and no relevant increase in reticulin. A comparison of clinical data and BM morphology reveals that biomarkers (EPO, EECs, PRV-1, JAK2) show an overlapping pattern of positivity between the different subtypes of MPDs.

Spontaneous megakaryocytic colony formation does not discriminate between essential thrombocythemia and polycythemia vera

Laboratory detection of spontaneous growth of colony-forming unit-megacaryocytes (CFU-MK), allowing us to distinguish essential thrombocythemia (ET) from reactive thrombocytosis, is therefore useful for the diagnostic of this myeloproliferative disorder. Whether CFU-MK assays allow us to discriminate at least partly between ET and other myeloproliferative disorders such as polycythemia vera (PV) remains, however, to be established. To gain insights about this point, we have performed CFU-MK cultures from bone marrow cells of patients diagnosed with ET (n = 42) or PV (n = 50) using a standardized collagen-based serum-free method. Spontaneous growth of CFU-MK was similarly detected in both 40/42 patients with ET and 47/50 patients with PV. These data suggest clearly that the CFU-MK assay is useful to detect not only ET, but also PV, but fails to discriminate, even partly, between these two myeloproliferative disorders.

Essential thrombocythemia: scientific advances and current practice

PURPOSE OF REVIEW

Median survival in essential thrombocythemia exceeds 20 years and clinical course is usually indolent with a minority of patients experiencing thrombohemorrhagic complications. Leukemic, polycythemic, or fibrotic disease transformation in essential thrombocythemia is an infrequent occurrence with a 15-year cumulative risk of approximately 5% or less in each instance. The major incentives for this review have been the recent description of an activating JAK2 tyrosine kinase mutation (JAK2 (V617F)) in essential thrombocythemia, related myeloproliferative disorders, and the impact on clinical practice from the publication of a major treatment trial.

RECENT FINDINGS

Several studies have reported on the occurrence of JAK2(V617F) in approximately 50% of patients with essential thrombocythemia and its presence has been associated with advanced age at diagnosis, higher hemoglobin and leukocyte levels, and increased rate of polycythemic transformation. In contrast, the mutation did not appear to affect the incidence of thrombotic, leukemic, or fibrotic events. There is increasing evidence regarding the thrombogenic role of neutrophils in essential thrombocythemia and this might partly explain the superior overall performance by hydroxyurea, compared with anagrelide, in a recent randomized study.

SUMMARY

Although it is in vogue to consider essential thrombocythemia as more than one disease in terms of both molecular phenotype (presence or absence of JAK2(V617F)) and putative pattern of myelopoiesis (monoclonal versus polyclonal), it is yet to be shown that such differences influence either the natural history of the disease or current therapy. From a treatment standpoint, hydroxyurea is now confirmed to be the drug of choice for high-risk patients with essential thrombocythemia.

Anagrelide: a review of its use in the management of essential thrombocythaemia

Anagrelide (Agrylin, Xagrid) is an oral imidazoquinazoline agent which is indicated in Europe for the reduction of elevated platelet counts in at-risk patients with essential thrombocythaemia who are intolerant of or refractory to their current therapy, and in the US for the reduction of elevated platelet counts and the amelioration of thrombohaemorrhagic events in patients with thrombocythaemia associated with myeloproliferative disorders. Anagrelide is well established as an effective platelet-lowering agent in most patients with essential thrombocythaemia, including both treatment-naive patients and those refractory to other cytoreductive therapy. Results of the only randomised trial to date (the Primary Thrombocythaemia 1 [PT1] study) indicated that the composite primary endpoint (arterial or venous thrombosis, serious haemorrhage or death from vascular causes) occurred more often in recipients of anagrelide plus aspirin than in those receiving hydroxycarbamide (hydroxyurea) plus aspirin. This trial also indicated that the incidence of the secondary endpoints transient ischaemic attack and gastrointestinal bleeding favoured hydroxycarbamide plus aspirin, while the incidence of venous thrombosis favoured anagrelide plus aspirin. There were no differences between the groups in the incidence of secondary endpoints myocardial infarction, stroke, unstable angina, pulmonary embolism, hepatic-vein thrombosis, other serious haemorrhage or related deaths. The design of the PT1 study has been queried with respect to the heterogeneous nature of the study population (possible inclusion of patients with early myelofibrotic disease) and the concomitant use of aspirin (interaction with anagrelide causing increased bleeding events). Further data are therefore required before the role of anagrelide in essential thrombocythaemia can be finalized. In the meantime, when considering treatment options for patients with this disorder, anagrelide's positive effects on platelet function, lack of mutagenicity and lack of association with leukaemia or angiogenesis must be balanced against its comparative expense and positive inotropic effects. Thus, the role of anagrelide in the management of high-risk patients with essential thrombocythaemia will ultimately depend on individual patient assessment and future clarification of the potential leukaemogenicity of hydroxycarbamide.

JAK2 mutation in essential thrombocythaemia: clinical associations and long-term prognostic relevance

Clinical correlates and long-term prognostic relevance of the JAK2(V617F) mutation was studied in 150 patients with essential thrombocythaemia (ET) from a single institution and followed for a median of 11.4 years. During this period, thrombotic complications were documented in 62 patients (41.3%) and transformation into acute myeloid leukaemia (AML), polycythaemia vera (PV), or myelofibrosis with myeloid metaplasia (MMM) occurred in 4 (2.7%), 8 (5.3%), and 15 (10%) patients, respectively. JAK2(V617F) was detected in either archived bone marrow or blood cells from 73 patients (48.7%) but none were homozygous for the mutant allele. Parameters at diagnosis that were significantly associated with the presence of JAK2(V617F) included advanced age and higher counts of both haemoglobin and leucocytes. During follow-up, patients with the mutation were more likely to transform into PV but the incidences of AML, MMM, or thrombotic events were similar between patients with and without the mutation. Multivariate analysis identified advanced age, higher haemoglobin level, and thrombosis history but not the presence of JAK2(V617F) as independent predictors of inferior survival. Therefore, although the presence of JAK2(V617F) in ET appears to promote a PV phenotype, it might not carry treatment-relevant information.

Platelets and Thrombosis in Myeloproliferative Diseases

The myeloproliferative disorders have been the “poor cousins” in the family of hematological malignancies for some time. Recently this field has advanced considerably with the description of a mutation in the JAK2 kinase detectable in the majority of patients and the publication of two landmark clinical trials—ECLAP and MRC PT1. But although both ECLAP and MRC PT1 inform clinical management and allude to the complexities of thrombosis we still lack fundamental knowledge, and our understanding of thrombosis in these conditions has not paralleled advances in the field of thrombosis and vascular biology. The predominant clinical complications of essential thrombocythemia and polycythemia vera are thrombotic and hemorrhagic; these significantly impact upon prognosis and quality of life. Here the current status of our knowledge is reviewed with specific emphasis upon the role of the platelet in the pathogenesis of thrombosis as well as the impact of recent data from ECLAP and MRC PT1.