Neutrophil-lymphocyte ratio and carotid plaque burden in patients with essential thrombocythemia and polycythemia vera.

BACKGROUND AND AIMS: Chronic inflammation plays a critical role in the pathogenesis of myeloproliferative neoplasm (MPN), and inflammatory conditions are closely related to the development and exacerbation of atherosclerosis. This study aimed to compare carotid plaque burden and neutrophil-lymphocyte ratio (NLR) in the essential thrombocythemia (ET)/polycythemia vera (PV) and control groups. METHODS AND RESULTS: We retrospectively assessed carotid plaque burden and NLR in patients with ET/PV between January 2010 and September 2021 and propensity-score matched these patients to control subjects from the general population. All patients underwent carotid imaging using carotid ultrasonography for atherosclerosis screening. After 3:1 propensity-score matching, 140 patients in the control group were matched to 51 patients in ET/PV group. The mean NLR was significantly higher in the MPN group than in the control group (4.77 ± 3.96 vs. 1.93 ± 1.03, p < 0.001). The carotid plaque score was also higher in MPN group than in the control group (2.37 ± 1.47 vs. 1.94 ± 1.17, p = 0.038). CONCLUSION: Patients with PV/ET show a higher NLR and carotid plaque burden than the normal population. This reflected that PV/ET was a highly inflammatory and atherosclerotic condition expressing potentially increased cardiovascular risk.

Treatment options and pregnancy management for patients with PV and ET.

Polycythemia vera (PV) and essential thrombocythemia (ET) are the two most common subtypes of Philadelphia chromosome-negative myeloproliferative neoplasm (MPN). PV results in erythrocytosis and ET in thrombocytosis. The discovery of JAK2 mutations in the majority of patients with MPN over the last 2 decades has led to the development of JAK inhibitors. Because PV and ET progress relatively slowly, the main treatment strategy for these two diseases is to prevent thrombotic complications. The first-line agent for both PV and ET is hydroxyurea, although some patients are intolerant or refractory to this compound and need other treatment options. Notably, hydroxyurea is contraindicated during pregnancy. In addition to JAK inhibitors, several new agents, such as HDAC inhibitors, LSD1 inhibitors, MDM2 inhibitors and hepcidin mimetics, have been developed as treatment options. Classical agents, such as busulfan and interferon, are still used to treat patients with PV or ET as well. Based on this context, treatment options and pregnancy management for patients with PV or ET are discussed in this review.

Clinical outcomes of interferon therapy for polycythemia vera and essential thrombocythemia: a systematic review and meta-analysis.

Interferon therapy has been used in clinical practice for more than three decades to treat polycythemia vera (PV) and essential thrombocythemia (ET). However, there has been no systematic investigation of its expected outcomes and potential risks. We performed a systematic review and single-arm meta-analysis to assess the clinical outcomes (hematological response, molecular response, vascular events, hematological transformation, and adverse events) after interferon therapy for patients with PV and ET. A systematic search identified 37 reports, including data from 1794 patients that were published before March 2021. The pooled overall hematological response (OHR) rate was 86%, with better OHR rates observed in studies using long-acting interferon (p < 0.001) and studies with younger patients (p = 0.038). The pooled overall molecular response rate was 48%, and inter-study heterogeneity was also related to patient age (p = 0.009). The overall incidence was 0.42/100 person-years for thrombosis, 0.01/100 person-years for hemorrhage, 0.21/100 person-years for myelofibrotic transformation, and 0.08/100 person-years for leukemic transformation. Compared with hydroxyurea, interferon produced a non-inferior hematological response and a superior molecular response. In conclusion, interferon therapy provided high rates of hematological and molecular response for patients with PV and ET and was associated with a favorable prognosis.

Evaluation of beta-2 microglobulin, erythropoietin and tobacco use in polycythemic cases.

In the 2016 WHO classification, hemoglobin and hematocrit thresholds for diagnosing polycythemia vera (PV) have been lowered, increasing the number of consultations for polycythemia investigations. In PV, beta-2 microglobulin (B2m) levels are reportedly increased, whereas erythropoietin (EPO) levels are usually low. Most secondary polycythemia cases (SP) are caused by tobacco use. We decided to analyze the relevance of these three parameters in all patients seen for polycythemia investigations to help differentiate PV from SP cases. A cohort of 257 patients (123 PV; 134 SP) was identified. The median B2m level was higher for PV patients (3.16 vs 1.98 mg/l, p < 0.0001). Increased B2m levels were observed in 83.7% of PV patients (11.9% in SP). The median EPO level was lower in PV patients (4.4 vs 12.3 UI/l, p < 0.0001). Tobacco was used by 42.8% of SP patients (8% in PV, p < 0.0001). Increased B2m, low EPO and no tobacco exposure was predictive of PV (specificity and positive predictive value = 100%). Normal B2m, normal EPO and tobacco exposure was predictive of SP (positive predictive value = 100%). These simple and inexpensive parameters could be used to rapidly differentiate PV from SP cases, before prescribing time-consuming JAK2 V617F mutation analysis by specialists.

MOLECULAR GENETIC ABNORMALITIES IN THE GENOME OF PATIENTS WITH Ph-NEGATIVE MYELOPROLIFERATIVE NEOPLASIA AFFECTED BY IONIZING RADIATION AS A RESULT OF THE CHORNOBYL NUCLEAR ACCIDENT. / MOLEKULIaRNO-GENETYChNI ANOMALIÏ U GENOMI KhVORYKh NA Rh-NEGATYVNI MIIeLOPROLIFERATYVNI NEOPLAZIÏ, IaKI ZAZNALY DIÏ IONIZUIuChOÏ RADIATsIÏ VNASLIDOK AVARIÏ NA ChAES.

OBJECTIVE: to determine the frequency of major somatic mutations in the JAK2, MPL and CALR genes in the genomeof patients with Ph-negative myeloproliferative neoplasms that occur in individuals who have been exposed to ionizing radiation as a result of the Chornobyl accident. MATERIALS AND METHODS: Molecular genetic analysis of genomic DNA samples isolated from blood was performed in90 patients with Ph-negative myeloproliferative neoplasia (MPN) with a history of radiation exposure and 191patients with spontaneous MPN utilizing allele-specific polymerase chain reaction (PCR). RESULTS: The presence of major mutations in the genes JAK2, CALR and MPL was revealed in patients with MPN witha history of radiation exposure with a frequency 58.9 % (53 of 90), 12.2 % (11 of 90), and 0 % respectively, and without exposure with frequency 75.4 % (144 of 191), 3.1 % (6 out of 191) and 1.6 % (3 out of 191) respectively.Mutations JAK2 V617F in patients with spontaneous MPN were observed in each clinical form: polycythemia vera (PV),essential thrombocythemia (ET) and primary myelofibrosis (PMF). CALR mutations were detected exclusively inpatients with PMF and ET, significantly more often in groups with a radiation exposure history (18.9 % and 33.3 %,vs. 4.2 % and 6.5 %) than without one. At the same time, the occurence of MPL mutations was determined only inpatients with spontaneous MPN in 1.6 % of casees. Triple negative mutation status of genes JAK2, MPL and CALR prevailed in the group of patients with MPN with a history of radiation exposure and was 27.8 %, against 16.2 % inpatients without radiation exposure (p = 0.05). CONCLUSIONS: Genomic research of patients with Ph-negative MPN revealed features of molecular genetic damage inthose patients who were exposed to IR as a result of the Chornobyl accident and those with spontaneous MPN. Thedata obtained by determining of JAK2, MPL and CALR genes mutational status in the genome of patients with MPN isnecessary to expand the understanding of the mechanism of leukogenesis, especially caused by radiation.

The advantages and risks of ruxolitinib for the treatment of polycythemia vera.

INTRODUCTION: Polycythemia vera is a myeloproliferative neoplasm characterized by an increased red blood cell mass, risk of thromboembolic events, and of transformation into secondary myelofibrosis and acute leukemia. The goal of treatment is to reduce the risk of fatal cardiovascular events reducing the hematocrit level with phlebotomies and low-dose aspirin. In high-risk patients (age >60 years or previous thromboembolic events) cytoreductive therapy is indicated. In this setting, resistance and/or intolerance is common. AREAS COVERED: Authors searched Medline, Embase, archives from the EHA and the ASH annual congresses from 2014 onward about ruxolitinib treatment in PV patients. Two trials (RESPONSE and RESPONSE2) have documented the efficacy and safety of ruxolitinib. The drug is able to persistently control the hematocrit level and symptoms (due to increased cytokine levels, increased viscosity, and increased splenomegaly), to reduce WBC counts and the rate of thromboembolic events, to increase the quality of life. EXPERT OPINION: Although ruxolitinib has entered into the clinical practice, the real-life incidence of resistant/intolerant patients, the long-term safety, and the activity on thromboembolic events (associated or not to a reduction of the molecular burden) remains to be conclusively determined. More information extrapolated by registries are required to shed light on the missing information.

The role of a low erythropoietin level for the polycythemia vera diagnosis.

A low erythropoietin (EPO) level is a minor diagnostic criterion for polycythemia vera (PV). Controversies exist regarding the diagnostic value of a low EPO level when considering increasing availability of advanced molecular testing. We assessed the role of low EPO level for PV diagnosis in the context of positive JAK2 mutation status as well as other diagnostic parameters. Of 138 patients, 75 patients had PV and 63 had secondary erythrocytosis. Of the 75 patients with PV, 32% had EPO levels within the normal range. EPO level positively correlated with obesity and smoking status, making it an unreliable diagnostic marker in those patients. Although EPO level below normal as a standalone diagnostic modality was significantly associated with PV (odds ratio [OR] 0.857; p < 0.001), when JAK2V617F mutation status was included in the prediction model, the association of low EPO was not statistically significant (OR 0.962, p = 0.269). Positive JAK2V617F demonstrated a strong predictive value for PV (OR 670.5, p = 0.006) either alone or in combination with other variables. Results show that EPO level is not a reliable diagnostic marker due to physiologic variation in association with obesity and smoking.

Marcaje de leucocitos con 99mTc-exametazima y policitemia vera: un hallazgo casual / Leucocyte labelling with 99mTc-exametazime and polycythemia vera: a casual finding

La clasificación oficial de la Organización Mundial de la Salud de los tumores de tejidos hematopoyéticos y linfoides de 2016 introduce el concepto de policitemia vera (PV) enmascarada y revela que esta entidad ha sido infradiagnosticada en el pasado. Se presenta el caso de un varón de 49 años, fumador, intervenido de fractura de tobillo hace más de 15 años, remitido para valorar un posible proceso infeccioso asociado. Al no producirse separación previa de los hematíes por sedimentación durante el procedimiento de marcaje de leucocitos con 99mTc-exametazima se revisaron las causas de disminución de la velocidad de sedimentación globular. Entre ellas destacan la poliglobulia y el hábito tabáquico, ambas presentes en el paciente. Se recomendó realización de estudio hematológico que concluyó con el diagnóstico de PV. Las indicaciones del especialista en Radiofarmacia permitieron diagnosticar un caso no identificado hasta entonces, pese a que el paciente presentaba síntomas desde hacía años

The official World Health Organization classification of hematopoietic and lymphoid tissue tumors introduces in 2016 the concept of masked polycythemia vera (PV) and reveals that this entity has been underdiagnosed in the past. We present the case of a 49-year-old man, smoker, operated on for ankle fracture more than 15 years ago, referred to evaluate a possible associated infectious process. As there was no previous separation of the red blood cells by sedimentation during the leukocyte labelling procedure with 99mTc-exametazima, the causes of decreased erythrocyte sedimentation rate were reviewed. These include polyglobulia and smoking, both present in the patient. A haematological study was advised, which concluded with the diagnosis of PV. The indications of the specialist in Radiopharmacy allowed diagnosing a case not identified until then, although the patient had had symptoms for years

Late polycythemic transformation in JAK2-mutated essential thrombocythemia patients-characteristics along with a validation of 2016 WHO criteria.

INTRODUCTION AND OBJECTIVES: The most common mutation within the spectrum of myeloproliferative neoplasms (MPNs) is a mutation in Janus kinase 2 gene (JAK2V617F). It has been observed that, during a course of disease, transformation from JAK2-mutated essential thrombocythemia (ET) to overt polycythemia vera (PV) can occur. Primary objective of this study was to show the incidence of mentioned phenomenon. METHODS: In this study, we analyzed data of 136 patients diagnosed with JAK2-positive ET observed for a median time of 9 years. We examined blood count of each patient at the time of diagnosis and confronted it with 2008 and 2016 WHO criteria for PV and mPV. Additionally, we analyzed JAK2V617F allele burden in two separate time points among selected cases. RESULTS: Confrontation with new criteria resulted in change of diagnosis to PV and mPV in 10% and 9% cases, respectively. Within remaining patients, 14 showed increasing hemoglobin concentration over several months during late course of disease, resulting in change of diagnosis to overt PV. We did not find suggested increase in JAK2 allele burden among transforming patients. CONCLUSIONS: Phenotype transformation to polycythemia was proven to be possible within the group of JAK2-mutated ET; however, cause of this effect remains uncertain.

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.

Oral idasanutlin in patients with polycythemia vera.

A limited number of drugs are available to treat patients with polycythemia vera (PV) and essential thrombocythemia (ET). We attempted to identify alternative agents that may target abnormalities within malignant hematopoietic stem (HSCs) and progenitor cells (HPCs). Previously, MDM2 protein levels were shown to be upregulated in PV/ET CD34+ cells, and exposure to a nutlin, an MDM2 antagonist, induced activation of the TP53 pathway and selective depletion of PV HPCs/HSCs. This anticlonal activity was mediated by upregulation of p53 and potentiated by the addition of interferon-α2a (IFN-α2a). Therefore, we performed an investigator-initiated phase 1 trial of the oral MDM2 antagonist idasanutlin (RG7388; Roche) in patients with high-risk PV/ET for whom at least 1 prior therapy had failed. Patients not attaining at least a partial response by European LeukemiaNet criteria after 6 cycles were then allowed to receive combination therapy with low-dose pegylated IFN-α2a. Thirteen patients with JAK2 V617F+ PV/ET were enrolled, and 12 (PV, n = 11; ET, n = 1) were treated with idasanutlin at 100 and 150 mg daily, respectively, for 5 consecutive days of a 28-day cycle. Idasanutlin was well tolerated; no dose-limiting toxicity was observed, but low-grade gastrointestinal toxicity was common. Overall response rate after 6 cycles was 58% (7 of 12) with idasanutlin monotherapy and 50% (2 of 4) with combination therapy. Median duration of response was 16.8 months (range, 3.5-26.7). Hematologic, symptomatic, pathologic, and molecular responses were observed. These data indicate that idasanutlin is a promising novel agent for PV; it is currently being evaluated in a global phase 2 trial. This trial was registered at www.clinicaltrials.gov as #NCT02407080.

Perspectives on interferon-alpha in the treatment of polycythemia vera and related myeloproliferative neoplasms: minimal residual disease and cure?

The first clinical trials of the safety and efficacy of interferon-alpha2 (IFN-alpha2) were performed about 30 years ago. Since then, several single-arm studies have convincingly demonstrated that IFN-alpha2 is a highly potent anti-cancer agent in several cancer types but unfortunately not being explored sufficiently due to a high toxicity profile when using non-pegylated IFN-alpha2 or high dosages or due to competitive drugs, that for clinicians at first glance might look more attractive. Within the hematological malignancies, IFN-alpha2 has only recently been revived in patients with the Philadelphia-negative myeloproliferative neoplasms-essential thrombocytosis, polycythemia vera, and myelofibrosis (MPNs)-and in patients with chronic myelogenous leukemia (CML) in combination with tyrosine kinase inhibitors. In this review, we tell the IFN story in MPNs from the very beginning in the 1980s up to 2018 and describe the perspectives for IFN-alpha2 treatment of MPNs in the future. The mechanisms of actions are discussed and the impact of chronic inflammation as the driving force for clonal expansion and disease progression in MPNs is discussed in the context of combination therapies with potent anti-inflammatory agents, such as the JAK1-2 inhibitors (licensed only ruxolitinib) and statins as well. Interferon-alpha2 being the cornerstone treatment in MPNs and having the potential of inducing minimal residual disease (MRD) with normalization of the bone marrow and low-JAK2V617F allele burden, we believe that combination therapy with ruxolitinib may be even more efficacious and hopefully revert disease progression in many more patients to enter the path towards MRD. In patients with advanced and transforming disease towards leukemic transformation or having transformed to acute myeloid leukemia, "triple therapy" is proposed as a novel treatment modality to be tested in clinical trials combining IFN-alpha2, DNA-hypomethylator, and ruxolitinib. The rationale for this "triple therapy" is given, including the fact that even in AML, IFN-alpha2 as monotherapy may revert disease progression. We envisage a new and bright future with many more patients with MPNs obtaining MRD on the above therapies. From this stage-and even before-vaccination strategies may open a new horizon with cure being the goal for some patients.

EVALUATION OF BURDENSOME SYMPTOMS IN PATIENTS WITH RADIATION6ASSOCIATED AND SPONTANEOUS MYELOPROILIFERATIVE NEOPLASMS WITH THE USE OF OPTIMIZED SELF-ASSESSMENT MPN-SAF TSS. / OTsINKA OBTIaZhLYVYKh SYMPTOMIV U KhVORYKh NA RADIATsIINO-ASOTsIIOVANI TA SPONTANNI MIIeLOPROLIFERATYVNI NEOPLAZIÏ Z VYKORYSTANNIaM ADAPTOVANOÏ ShKALY SAMOOTsINKY MPN-SAF TSS.

OBJECTIVE: To investigate the intensity of burdensome symptoms using self-assessment MPN-SAF TSS in patientswith radiation-associated and spontaneous myeloproiliferative neoplasms (MPNs). MATERIALS AND METHODS: The study included 89 patients with radiation-associated and spontaneous MPNs, the bur-densome symptoms of MPN were determined using MPN-SAF TSS. RESULTS: The average score for complaints in patients with radiation-associated MPNs was significantly higher thanin patients with spontaneous MPNs - 43.46 and 25.04 points, respectively (p = 0.003). MPN patients classified bysubtypes also showed differences regarding intensity of burdensome MPN symptoms, demonstrating significantlyhigher average score of complaints among primary myelofibrosis patients (35.60), compared to polycythemia vera(29.60) and essential thrombocythemia (18.05) patients, (p = 0.005). Our study did not reveal any influence of theJAK2 V617F mutation on MPN burdensome symptoms intensity in MPN patients. CONCLUSIONS: We demonstrated a higher intensity of the MPN burdensome symptoms determined by the optimizedself-assessment MPN-SAF TSS in patients with radiation-associated, and in primary myelofibrosis patients, indicat-ing increased severity of patient's general conditions at the stage of diagnosis verification. It is advisable to usethe optimized MPN-SAF TSS at the moment of molecular genetic testing during the diagnosis of MPN for selectionor modifying treatment strategies in order to achieve better quality of life for patients.

Clinical and Disease Characteristics From REVEAL at Time of Enrollment (Baseline): Prospective Observational Study of Patients With Polycythemia Vera in the United States.

BACKGROUND: Polycythemia vera (PV) has a prevalence of 44 to 57 per 100,000 people in the United States. Prospective data concerning the demographics, clinical characteristics, and treatment patterns of patients with PV in the United States are lacking. PATIENTS AND METHODS: The ongoing, prospective, observational REVEAL study evaluates demographics, disease burden, clinical management, patient-reported outcomes, and health care resource utilization of adult patients with PV in the United States. This report summarizes the demographics and clinical characteristics of patients at enrollment (baseline). RESULTS: Patients (n = 2510) were a median age of 67.0 years, 54.2% were male, and 89.1% were white. The median time from PV diagnosis to study enrollment was 4.0 (range, 0-56.3) years. Most patients (89.7%) were diagnosed after an abnormal blood test. Less than half (49.2%) underwent JAK2 mutation analysis, of whom 95.8% were JAK2 V617F mutation positive; < 1% were positive for JAK2 exon 12 mutations. At enrollment, 47.7% of patients had elevated hematocrit (> 45%), 35.8% had elevated platelets (> 400 × 109/L), and 37.0% had elevated leukocytes (> 10 × 109/L). Most patients (94.5%) were receiving active PV treatment, predominantly therapeutic phlebotomy alone (33.6%), hydroxyurea monotherapy (29.0%), or hydroxyurea plus phlebotomy (23.7%). Thrombotic events occurred in 11.9% of patients before PV diagnosis (venous, 6.7%; arterial, 5.7%), and 8.3% between diagnosis and enrollment. Hypertension (70.6%) was the most common previous medical condition. CONCLUSION: REVEAL enrollment data inform our understanding of the baseline demographics, diagnostic approach, disease characteristics, and treatment patterns of patients with PV in the United States. Longitudinal real-world data collected in this study will complement information collected during randomized controlled clinical trials.

Safety and efficacy of combination therapy of interferon-α2 and ruxolitinib in polycythemia vera and myelofibrosis.

Interferon-α2 reduces elevated blood cell counts and splenomegaly in patients with myeloproliferative neoplasms (MPN) and may restore polyclonal hematopoiesis. Its use is limited by inflammation-mediated toxicity, leading to treatment discontinuation in 10-30% of patients. Ruxolitinib, a potent anti-inflammatory agent, has demonstrated benefit in myelofibrosis (MF) and polycythemia vera (PV) patients. Combination therapy (CT) with these two agents may be more efficacious than monotherapy with either, potentially improving tolerability of interferon-α2 as well. We report the preliminary results from a phase II study of CT with pegylated interferon-α2 and ruxolitinib in 50 MPN patients (PV, n = 32; low-/intermediate-1-risk MF, n = 18), the majority (n = 47) being resistant and/or intolerant to interferon-α2 monotherapy. Objectives included remission (2013 revised criteria encompassing histologic, hematologic, and clinical responses), complete hematologic response (CHR), molecular response, and toxicity. Follow-up was 12 months. Partial remission (PR) and sustained CHR were achieved in 9% and 44% of PV patients, respectively. In MF patients, complete or partial remission was achieved in 39%, and sustained CHR in 58%. The median JAK2V617F allele burden declined significantly in both groups. Hematologic toxicity was the most common adverse event and was managed by dose reduction. Thirty-seven serious adverse events were recorded in 23 patients; the discontinuation rate was 20%. We conclude that CT with interferon-α2 and ruxolitinib is efficacious in patients with low-/intermediate-1-risk MF and, to a lesser extent, in patients with PV. These preliminary results encourage phase III studies as well as a study with CT in newly diagnosed MPN patients.

Polycythemia Vera.

OPINION STATEMENT: Polycythemia vera (PV) is the most common myeloproliferative neoplasm (MPN), the ultimate phenotype of the JAK2 V1617F mutation, the MPN with the highest incidence of thromboembolic complications, which usually occur early in the course of the disease, and the only MPN in which erythrocytosis occurs. The classical presentation of PV is characterized by erythrocytosis, leukocytosis, and thrombocytosis, often with splenomegaly and occasionally with myelofibrosis, but it can also present as isolated erythrocytosis with or without splenomegaly, isolated thrombocytosis or isolated leukocytosis, or any combination of these. When PV is present, the peripheral blood hematocrit (or hemoglobin) determination will not accurately represent the actual volume of red cells in the body, because in PV, in contrast to other disorders causing erythrocytosis, when the red cell mass increases, the plasma volume usually increases. In fact, unless the hematocrit is greater than 59%, true erythrocytosis cannot be distinguished from pseudoerythrocytosis due to plasma volume contraction. Usually, the presence of splenomegaly or leukocytosis or thrombocytosis establishes the diagnosis. However, when a patient presents with isolated thrombocytosis and a positive JAK2 V617F assay, particularly a young woman, the possibility of PV must always be considered because of plasma volume expansion. The WHO PV diagnostic guidelines are not helpful in this situation, since the hematocrit is invariably normal and a bone marrow examination will not distinguish ET from PV. Only a direct measurement of both the red cell mass and plasma volume can establish the correct diagnosis. In managing a PV patient, it is important to remember that PV is an indolent disorder in which life span is usually measured in decades, even when myelofibrosis is present, that chemotherapy is futile in eradicating the disease but does increase the incidence of acute leukemia and that hydroxyurea is not safe in this regard nor is it antithrombotic. Phlebotomy to a sex-specific normal hematocrit is the cornerstone of therapy and there now exist safe remedies for controlling leukocytosis, thrombocytosis, and extramedullary hematopoiesis and symptoms due to inflammatory cytokines when this is necessary.