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Essential thrombocythemia is a distinct clinical entity within the spectrum of myeloproliferative disorders. There is as yet no pathognomonic diagnostic test, and patients who currently fall into the category of essential thrombocythemia are likely to be heterogeneous. This article discusses diagnostic criteria, clinical features, prognosis, and management.
Essential thrombocythemia is a clonal myeloproliferative disorder, characterized predominantly by a markedly elevated platelet count without known cause. We report a case that was recognized during investigation of a transient ischemic attack, and review the neurologic findings in 33 patients with unequivocal essential thrombocythemia under prospective study by the Polycythemia Vera Study Group. Twenty-one patients had neurologic manifestations at some point during their course, including headache (13 patients), paresthesiae (10), posterior cerebral circulatory ischemia (9), anterior cerebral circulatory ischemia (6), visual disturbances (6) and epileptic seizures (2). All patients with neurologic symptoms responded satisfactorily to treatment, although continuous or repeated treatment was often required. Therapeutic recommendations include plateletpheresis for major thrombo-hemorrhagic phenomena, or megakaryocyte suppression with radioactive phosphorus, alkylating agents (such as melphalan), or hydroxyurea; minor symptoms may respond to platelet antiaggregating agents.
Essential thrombocythemia is a disorder that causes persistent increase in the platelet count. The disease is associated with an elevated risk of thrombosis. A 71-year-old woman was diagnosed with left main coronary thrombosis after an angiogram due to stable angina. One week before the angiogram was taken the patient had also been diagnosed with essential thrombocythemia. After appropriate medical treatment for 5 days the patient underwent an excimer laser treatment, which failed in dissolving the thrombus. Before the patient underwent coronary surgery, thrombopheresis was performed in order to reduce the platelet count. After a successful coronary operation the patient improved completely.
Essential thrombocythemia is a myeloproliferative disorder characterized by frequent bleeding and thrombotic complications. On a molecular level, two abnormalities of platelet thrombospondin have been identified: abnormal glycosylation of the intact 185,000-dalton chain has been detected and a shortened form of the thrombospondin chain is present. We have used two monoclonal antibodies and Lens culinaris lectin to probe the structure of thrombospondin in the platelets from three patients with essential thrombocythemia; one patient with polycythemia vera and two patients with secondary thrombocytosis. The presence of abnormal thrombospondin fragments with molecular weights of 160,000 and 30,000 was detected in the intact platelets and in the supernatant from thrombin-treated platelets, in all of the individuals except one of the secondary thrombocytosis patients. Monoclonal antibody binding studies indicate that both fragments are produced by proteolysis at a single site, which results in the removal of a 30,000-dalton fragment from the NH2-terminal. Lens culinaris lectin-binding studies revealed that some of the carbohydrate moieties of thrombospondin are near this cleavage site. The results are consistent with the hypothesis that the abnormal thrombospondin fragments observed under conditions of increased platelet production are due to increased susceptibility to proteolysis which, in turn, may be due to defective glycosylation.
Essential thrombocythemia (ET) is a clonal myeloproliferative disorder characterized by an elevation of platelets in peripheral blood and excessive proliferation of megakaryocytes in bone marrow. The pathological mechanisms for the elevation of megakaryocytes and platelets in ET remain unclear. To study the hypersensitivity of megakaryocyte progenitors to thrombopoietin (TPO), a 9-year-old girl, diagnosed with ET, underwent dose-response experiments with recombinant human TPO, using her bone marrow non-adherent mononuclear cells and CD34 positive cells. Spontaneous colony-forming unit-megakaryocytes (CFU-Meg) were observed in serum-deprived cultures of non-adherent mononuclear cells, whereas they disappeared in cultures of CD34 positive cells. The patient's CFU-Meg showed maximal growth at concentrations of TPO lower than those for normal children. Dose-response curves demonstrated a 50-80 fold increase in sensitivity of the patient's CFU-Meg to TPO. We observed hypersensitivity of megakaryocyte progenitors to TPO in a child with ET. Our results suggest that spontaneous CFU-Meg formation in patients with ET may be due to hypersensitivity to TPO.
Essential thrombocythemia (ET) is a heterogeneous disorder. For example, the growth of erythropoietin-independent erythroid colonies, termed "endogenous erythroid colonies (EECs)", has previously been observed in only 50% of ET patients. We have recently described the overexpression of a hematopoietic receptor, PRV-1 (polycythemia rubra vera-1), in patients with polycythemia vera (PV). Here, we compare PRV-1 expression and EEC formation in a cohort of 30 patients with ET; 50% of the ET patients in our cohort displayed EEC growth. Likewise, 50% of the ET patients overexpressed PRV-1. Remarkably, only the 15 ET patients displaying EEC growth showed elevated PRV-1 expression, while the 15 EEC-negative ET patients expressed normal PRV-1 levels. It has previously been reported that EEC-positive ET patients develop PV during long-term follow-up. Here, we show that 40% of the PRV-1-positive patients develop symptoms of PV during the course of their disease. In contrast, none of the 15 PRV-1-negative patients displayed such symptoms (p=0.017). Moreover, PRV-1-positive patients had a significantly higher number of thromboembolic or microcirculatory events (p=0.003). We propose that PRV-1-positive ET comprise a pathophysiologically distinct subgroup of patients, one that is at risk for the development of complications and for the emergence of PV.
Essential thrombocythemia (ET) is a myeloproliferative disorder associated with megakaryocytic hyperplasia and thrombocytosis. In this disease, in vitro autonomous growth of megakaryocytic colonies has been demonstrated by various investigators. This phenomenon is impaired by the inhibition of the thrombopoietin/c-mpl pathway. In order to evaluate the potential role of mutations of the receptor gene in the origin of this autonomous growth, we compared the expression of c-mpl mRNA isoforms in platelets derived from ET patients and normal subjects. Overlapping c-mpl PCR fragments derived from four ET patients were sequenced to search for small mutations. In the 10 ET and five normal samples we studied, relative expression of the c-mpl isoforms was identical. New variants of Mpl-P and K isoforms, Mpl-P2 and K2 were detected. Cloning of these isoforms indicated that they are produced by alternative splicing of exon 9 sequences shared by Mpl-P and K. Their predicted amino acid sequence would be deleted by 24 aminoacids, upstream of the WSSWS box of the second domain of c-mpl. Two sequence variations, leading to DNA restriction polymorphisms, were present in the extracellular and Mpl-K intracytoplasmic domains. Both were present in normal and ET samples, excluding mutations of c-mpl as a cause of ET.
Essential thrombocythemia (ET), one of the chronic myeloproliferative disorders, exposes individuals to significantly increased risk for thrombohemorrhagic complications. Epidemiologic data indicate that the two most prominent risk factors for thrombosis are age greater than 60 years or a history of or presentation with thrombosis at any age. Age is an important factor in selecting among therapeutic options, as the agents used to treat ET may contribute to acute leukemic transformation and other secondary malignancies. Whether or not hydroxyurea (HU) carries these risks is controversial and unresolved, but the uncertainty is a basis for avoiding it in young patients. Alternatives to HU that have established efficacy in lowering platelet counts in ET are interferon and anagrelide. Both are highly effective in reducing platelet numbers, and are apparently not associated with leukemogenicity or mutagenicity. However, approximately 30% of patients find interferon intolerable for long-term therapy. Anagrelide offers the advantage of oral dosing and long-term effectiveness at managing platelet counts. A recent long-term study of young ET patients treated with anagrelide found that all thrombohemorrhagic events occurred in patients with platelet counts greater than 0.4 x 10(9)/L, adding to the evidence that reduction of platelet counts to normal may be required for optimal control of risk.
Essential thrombocythemia (ET) is a myeloproliferative disorder characterized by marked thrombocytosis with associated hemorrhagic, thrombotic and embolic complications caused by platelet dysfunction. In this report we describe two cases of ET and moderate to severe hypertension associated with renal artery stenosis and renal microvascular lesions. In both cases treatment of the hematologic disorder resulted in reduction of blood pressure and improvement of clinical symptoms.
Essential thrombocythemia, a myeloproliferative disorder of clonal origin, is often associated with various clinical manifestations resulting from thromboembolic or hemorrhagic complications. The long-established successful method of treatment with cytotoxic agents or radioactive phosphorus has recently been superseded by interferon alpha. We treated 14 symptomatic patients with 5 x 10(6) IU recombinant interferon alpha-2b s.c. daily. 12/14 pts responded within 14-75 days. When platelet counts decreased to below 450 g/l the frequency of administration was reduced stepwise. 7 patients remained in CR during this reduction phase and treatment was stopped in 5 pts after 12-32 months. Until now, 3 of them are still in continuous good PR without any drug therapy and free of symptoms for 3+, 19+ and 36+ months. Continuous response during maintenance was associated with age, initial platelet count and time required to reduce platelet counts to less than 450 g/l.
Essential thrombocythemia (ET) is a chronic myeloid disorder that is characterized by thrombocytosis, thrombohemorrhagic and vasomotor symptoms, a long median survival, and a low risk of transformation to leukemia. ET can be difficult to distinguish from secondary (reactive) thrombocytosis, and the diagnosis of ET can only be made after the exclusion of other marrow disorders with similar features. Although ET has been assumed to be a clonal process, recent studies have suggested that a substantial number of cases classified as ET may actually not be clonal, and nonclonality may be associated with a lower risk of thrombosis. The lack of a characteristic cytogenetic marker for ET confounds analyses of clonality and offers no insight into disease pathogenesis. There is controversy over the proper classification of thrombocytosis associated with the pathological BCR-ABL gene rearrangement; such cases are not clearly distinguishable from chronic myelogenous leukemia (CML) and should be provisionally classified as CML. New insights are emerging into the role of the megakaryocytopoiesis regulator thrombopoietin (TPO) and its receptor, c-Mpl, in ET and related disorders, but TPO-Mpl dynamics appear to be complex. In some familial thrombocythemic syndromes, mutations in the 5' untranslated region of TPO have recently been described, but these have not yet been observed in sporadic ET. In the future, global analysis of gene expression patterns may help overcome diagnostic dilemmas, refine disease classification, and lead to an improved understanding of the pathogenesis of ET.
Essential thrombocythemia (ET) and polycythemia vera (PV) are chronic myeloproliferative disorders that share the involvement of a multipotent progenitor cell and dominance of the transformed clone over normal hematopoiesis. On the other hand, the heterogeneity of these diseases with respect to clonal development from a common progenitor has been well established. To identify useful prognostic indicators, we analyzed telomerase activity (TA), a known marker of neoplastic proliferation, in granulocytes (PMNs) and mononuclear cells (MNCs) from 22 female patients with ET and PV. Clonality status was determined by investigation of X chromosome inactivation patterns (XCIPs). We found a statistically significant positive correlation between high TA and monoclonal pattern of XCIP. Therefore, our data suggest that the use of multiple tumor markers may contribute to a better understanding of the deregulated physiology of these disorders and provide useful prognostic factors.
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.
Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterised by the absence of the Philadelphia (Ph+) chromosome. Recent studies have reported controversial results relating to BCR-ABL rearrangements in ET patients. We studied 44 Ph-negative ET patients with the RT-PCR technique at diagnosis or during the follow-up. None of them showed any of the BCR-ABL transcript actually described by others in ET; neither the "classical" P210 nor the P190 or P230 variants. Our results confirm the absence of BCR-ABL abnormalities in Ph-negative ET patients.
Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterized by increased risk of thrombosis and/or hemorrhages. Cytotoxic drugs are mostly used in patients at high risk for thrombotic complications, while their use is still debated in low risk patients because of the risk of leukemia or secondary neoplasm. We discuss the leukemic risk of available treatment strategies in a large cohort of patients. Over a 12 years period we treated 23 patients with busulfan (BU), 1 with pipobroman (Pi), 6 with 32P, 48 with hydroxyurea (HU) in 62 cases associated with acetyl salicylic acid (ASA) while 77 patients received ASA alone and 33 did not receive any therapy. We observed 2 cases of acute leukemia (AL) and 1 of myelodysplastic syndrome (MDS). One of these patients had been treated with 32P and Pi these after with and the other two with BU and HU. They represented 23% of all patients treated with more than 1 cytotoxic agent, 16.6% of 32P treated subjects, 4% of those with HU and 6.4% of those with BU. The case of MDS occurred in a 81 years old female and represents 4% of cases of ET over the 70 years of age. No cases of AL or MDS were observed in patients not receiving cytotoxic therapy (with or without ASA). According to our experience the use of more than one cytotoxic agent in ET confirms the increase in the risk of leukemia in these cases. However, none of the patients treated with HU alone, even for more than 10 years (12 cases) developed AL. No treatment or therapy with ASA alone may be the best choice in young patients with ET with a low risk of thrombotic complications.
Essential thrombocythemia (ET) was diagnosed in a 31-year-old woman who had a miscarriage in the first trimester of her first pregnancy. Because of her wish for child, the patient was given alpha interferon (alpha-IFN) instead of hydroxyurea or aspirin to lower her platelet count to about 80 x 10(4)/microliter. She also had a miscarriage in her second pregnancy. Thereafter, the platelet count was kept at 60-70 x 10(4)/microliter by dose escalation of alpha-IFN. In the 35th week of her third pregnancy, the patient delivered a healthy baby with a normal blood count. Several small infarctions were observed in the placenta. Control of platelet count by alpha-IFN administration was effective in preventing recurrent miscarriage associated with ET, and had no adverse effect on patient fertility or fetal development.
Essential thrombocythemia (ET) is a chronic myeloid disorder that is characterized by persistent thrombocytosis, thrombohemorrhagic symptoms and a low risk of transformation to leukemia. Chromosomal abnormalities in ET are very rare and most of the patients studied were either in leukemic transformation or they had received treatment with cytotoxic agents. The number of cases studied at the time of diagnosis is very limited. In the present study, 67 cases with ET, at the time of diagnosis, were cytogenetically studied by a G-banding technique. Among them, only four presented chromosomal abnormalities. In two cases, a del(5)(q13q33) was identified, accompanied by trisomy 20 in one case, while, in the other case, monosomy 17 and a small marker chromosome were additionally found. In each of the remaining two abnormal cases, clonal isolated trisomy 13 or monosomy 14 were found, respectively. Since these chromosomal abnormalities were found at the time of diagnosis, they might be related to the neoplastic process. The documentation of more cases of chromosomal abnormalities in ET at the time of diagnosis may facilitate the identification of candidate genes involved in the neoplastic process.
Essential thrombocythemia (ET) is a myeloproliferative disorder characterized by a platelet count higher than 1000 x 10(9)/l. Bone marrow karyotype aberrations are occasionally observed. The presence of cytogenetic and molecular markers of chronic myeloid leukemia (CML) was assessed in 25 patients with the clinical features of ET. One displayed a complex translocation (9; 15; 22) (q34.1 or q34.3; q26.1; q11), and another a Philadelphia chromosome with standard translocation (9; 22) (q34; q11). Southern blot analysis revealed a rearranged breakpoint cluster region (bcr) in each case. Both patients experienced a stormy disease course without a leukemic transformation. These data indicate that the Philadelphia chromosome rarely occurs in ET and strongly influences patient outcome.