Polycythemia vera and essential thrombocythemia: algorithmic approach.

PURPOSE OF REVIEW: To describe an algorithm-based approach, whenever available, to the diagnosis, the risk stratification criteria informing therapy and the current management of polycythemia vera and essential thrombocythemia. RECENT FINDINGS: Description of recurrent genetic abnormalities in driver genes, including Janus Kinase 2 (JAK2), myeloproliferative leukemia and calreticulin, a better appreciation of the key diagnostic role of bone marrow features, results of large epidemiologic studies and a few but landmark controlled clinical trials produced in the last decade, all resulted in a reappraisal of the approach to polycythemia vera and essential thrombocythemia. SUMMARY: The revised 2017 WHO classification of polycythemia vera and essential thrombocythemia allows early diagnosis and accurate distinction from other chronic myeloproliferative neoplasms, particulary prefibrotic myelofibrosis. The prognostic value of selected mutations is being appreciated and JAK2V617F mutation is currently incorporated as risk variable in prognostic system for essential thrombocythemia. Risk-adjusted stratification is used to select therapeutic approaches that include target agents. However, there is not yet a curative approach to these hematologic neoplasms, and although their management has much improved in the last decades, the associated morbidity and mortality remains significant and may be worsened by toxicities of therapeutic agents. Therefore, several clinically relevant endpoints remain unmet.

[Diagnosis and treatment of polycythaemia vera: state of the art]. / Újdonságok, aktualitások a polycythaemia vera diagnosztikájában és kezelésében.

Polycythaemia vera (PV), a condition characterized by blood hyperviscosity due to the expansion of the erythrocyte mass is the most common entity among all Philadelphia chromosome-negative myeloproliferative neoplasms. Arterial and venous thrombotic events are leading determinants of morbidity and mortality but impairment of quality of life due to vasomotor symptoms (erythromelalgia, pruritus) and disease-associated symptoms (tiredness, fatigue, pruritus, night sweats, vision problems, headache, concentration loss, abdominal discomfort, early satiety, fever, weight loss) are also present. The review of polycythaemia vera is actual as the updated WHO 2016 classification of myeloid neoplasms has changed the diagnostic criteria and a new second-line treatment option - JAK1/JAK2 inhibitor ruxolitinib - has been approved for patients who had an inadequate response to or are intolerant of hydroxyurea, which represents a breakthrough in the treatment of this patient population. Orv. Hetil., 2016, 157(44), 1743-1751.

[Diagnosis of latent polycythemia vera: A clinician's opinion]. / Diagnostika latentnoi istinnoi politsitemii (vzglyad klinitsista).

AIM: to identify the clinical features of latent polycythemia vera (PV) as an independent nosological entity. SUBJECTS AND METHODS: The investigation enrolled 81 patients (50 with extensive (manifest) PV and 31 with latent PV) who had visited the Outpatient Department, Hematology Research Center, Ministry of Health of Russia, in 2014 to October 2015. RESULTS: The gender distribution of the patients was statistically comparable in the analyzed groups. The patients with manifest PV were slightly older than those with latent PV: the median age in the compared groups was 56 and 44 years, respectively. Red blood cell counts, hemoglobin concentrations, and packed cell volume were higher in the patients with manifest PV. Blood platelet counts were higher in the latent PV group. There were no differences in the number of white blood cells in the compared groups. All the patients were JAK2 V617F mutation carriers. The JAK2 allele load was significantly higher in the manifest PV group than in the latent PV group. The compared patient groups differed in the rate of thromboses in the history or at diagnosis. In the patients with latent PV, thromboses were detected in 38% of cases versus 16% in those with manifest PV. In latent PV, there were mainly venous thromboses; abdominal vascular thromboses were diagnosed with a high frequency. Arterial thromboses were revealed in only 2 cases. CONCLUSION: Chronic myeloproliferative disease that is characterized by the JAK2 V617F mutation, borderline hemoglobin counts, and morphological features of a bone marrow trephine biopsy specimen, which are specific for PV, is an independent PV variant, namely: latent PV.

Two clinical phenotypes in polycythemia vera.

BACKGROUND: Polycythemia vera is the ultimate phenotypic consequence of the V617F mutation in Janus kinase 2 (encoded by JAK2), but the extent to which this mutation influences the behavior of the involved CD34+ hematopoietic stem cells is unknown. METHODS: We analyzed gene expression in CD34+ peripheral-blood cells from 19 patients with polycythemia vera, using oligonucleotide microarray technology after correcting for potential confounding by sex, since the phenotypic features of the disease differ between men and women. RESULTS: Men with polycythemia vera had twice as many up-regulated or down-regulated genes as women with polycythemia vera, in a comparison of gene expression in the patients and in healthy persons of the same sex, but there were 102 genes with differential regulation that was concordant in men and women. When these genes were used for class discovery by means of unsupervised hierarchical clustering, the 19 patients could be divided into two groups that did not differ significantly with respect to age, neutrophil JAK2 V617F allele burden, white-cell count, platelet count, or clonal dominance. However, they did differ significantly with respect to disease duration; hemoglobin level; frequency of thromboembolic events, palpable splenomegaly, and splenectomy; chemotherapy exposure; leukemic transformation; and survival. The unsupervised clustering was confirmed by a supervised approach with the use of a top-scoring-pair classifier that segregated the 19 patients into the same two phenotypic groups with 100% accuracy. CONCLUSIONS: Removing sex as a potential confounder, we identified an accurate molecular method for classifying patients with polycythemia vera according to disease behavior, independently of their JAK2 V617F allele burden, and identified previously unrecognized molecular pathways in polycythemia vera outside the canonical JAK2 pathway that may be amenable to targeted therapy. (Funded by the Department of Defense and the National Institutes of Health.).

Masked polycythemia vera diagnosed according to WHO and BCSH classification.

Polycythemia vera (PV) is currently diagnosed by the World Health Organization (WHO) criteria regarding hemoglobin (HB) levels and JAK2V617F and related mutations or by the British Committee for Standards in Haematology (BCSH) guidelines predominantly based on hematocrit (HCT) values (>52% in men and >48% in women) in JAK2 mutated patients. We examined clinical features at diagnosis and outcome in 397 mutated PV patients showing a bone marrow (BM) morphology conforming with the WHO descriptions but including also cases with a HB level <18.5 g/dL in males (range 16.0-18.4) and <16.5 g/dL in females (range 15.0-16.4). These patients were regarded as masked PV (mPV) comprising 140 (35%) cases of our cohort. A comparison with the BCSH criteria based on HCT levels revealed a decrease of mPV patients to 59 (15%). In both classification systems, mPV patients were more males, presented more frequently with higher platelet counts, and increased BM reticulin fibrosis. A worsening of overall survival was documented in mPV patients in comparison with overt PV following the WHO (P = 0.011) as well as the BCSH (P = 0.0019) criteria. Risk factors for inferior survival in mPV were age >65 years and white blood cell count >15 × 10(9) /L. Without these risk factors mPV patients had the same survival as overt PV suggesting that a fraction of patients with HB lower than that required for WHO diagnosis should still be considered as overt PV. This study has established the existence of mPV by two different classification systems based on either HB or HCT threshold values.

Erythroid proliferations in myeloid neoplasms.

Prominent erythroid proliferations (in which erythroid elements comprise ≥50% of total bone marrow cells) can be seen in various hematopoietic stem cell neoplasms. The myeloproliferative neoplasm polycythemia vera exhibits effective, overexuberant erythropoiesis resulting in an increased red blood cell mass; in contrast, most other diseases characterized by erythroid predominance exhibit ineffective hemopoiesis. The latter include acute erythroid leukemia (erythroid-myeloid and pure erythroid leukemia subtypes) as well as some cases of myelodysplastic syndromes, acute myeloid leukemia with myelodysplasia-related changes, and therapy-related myeloid neoplasms. Some nonneoplastic reactive conditions may also manifest a striking bone marrow erythroid predominance. In this article, we review the literature relevant to this group of diseases for a better understanding of their clinicopathologic features and surrounding controversies. We also examine the position of neoplastic erythroid proliferations in the current 2008 World Health Organization Classification of Myeloid Neoplasms and provide recommendations as to how to approach the differential diagnosis of this group of diseases.

How I treat myelofibrosis.

It is currently assumed that myelofibrosis (MF) originates from acquired mutations that target the hematopoietic stem cell and induce dysregulation of kinase signaling, clonal myeloproliferation, and abnormal cytokine expression. These pathogenetic processes are interdependent and also individually contributory to disease phenotype-bone marrow stromal changes, extramedullary hematopoiesis, ineffective erythropoiesis, and constitutional symptoms. Molecular pathogenesis of MF is poorly understood despite a growing list of resident somatic mutations that are either functionally linked to Janus kinase (JAK)-signal transducer and activator of transcription hyperactivation (eg JAK2, MPL, and LNK mutations) or possibly involved in epigenetic dysregulation of transcription (TET2, ASXL1, or EZH2 mutations). Current prognostication in primary MF is based on the Dynamic International Prognostic Scoring System-plus model, which uses 8 independent predictors of inferior survival to classify patients into low, intermediate 1, intermediate 2, and high-risk disease groups; corresponding median survivals are estimated at 15.4, 6.5, 2.9, and 1.3 years. Such information is used to plan a risk-adapted treatment strategy for the individual patient, which might include observation alone, conventional or investigational (eg, JAK inhibitors, pomalidomide) drug therapy, allogenic stem cell transplantation with reduced- or conventional-intensity conditioning, splenectomy, or radiotherapy. I discuss these treatment approaches in the context of who should get what and when.

Deregulated expression of A1, Bcl-2, Bcl-xL, and Mcl-1 antiapoptotic proteins and Bid, Bad, and Bax proapoptotic genes in polycythemia vera patients

Apoptosis deregulation might have a role in the pathophysiology of polycythemia vera (PV). This study evaluated Bcl-2 molecule expression in CD34+ cells and leukocytes in 12 PV patients. Gene expression was investigated by real time PCR using SybrGreen Quantitect kit and protein expression was evaluated by western-blotting. JAK2 V617F mutation was detected according to Baxter et al (2005). CD34+ cells from PV patients presented higher levels of A1 and Mcl-1 expression (median: 22.6 and 5.2, respectively) in comparison with controls (0.9 and 0.5, p=0.004 and p=0.020); while Bcl-2 and Bcl-xL expression decreased in PV patients (0.18 and 1.19) compared with controls (1.39 and 2.01, p=0.006 and p=0.020). CD34+ cells in PV patients showed an elevated Bid expression (14.4) in comparison with healthy subjects (1.0; p=0.002). Patients' leukocytes showed an A1 augmentation (7.41, p=0.001) and a reduced expression of Bax (0.19; p=0.040) and Bad (0.2; p=0.030). There was no correlation between JAK2 V617F allele burden and molecular expression. PV patients showed alterations in Bcl-2 members' expression, which may interfere with control of apoptotic machinery and contribute to disease pathogenesis.

A desregulação da apoptose parece participar da fisiopatologia da policitemia vera (PV). Este estudo avaliou a expressão das moléculas da família Bcl-2 em células hematopoéticas CD34 + e leucócitos de 12 pacientes com PV. Foram realizados: a quantificação da expressão gênica por PCR em tempo real utilizando kit Sybrgreen Quantitect, avaliação da expressão de proteínas por western-blot e detecção da mutação JAK2 V617F segundo Baxter et al. (2005). Células CD34 + dos pacientes com PV apresentaram maior expressão de A1 e Mcl-1 (mediana: 22,6 e 5,2, respectivamente) em comparação com controles (0,9 e 0,5, p = 0,004 e p = 0,020) e expressão de Bcl-2 e Bcl-xL diminuída nestes pacientes (0,18 e 1,19) em relação aos controles (1,39 e 2,01, p = 0,006 e p = 0,020). Células CD34 + dos pacientes com PV mostraram expressão elevada de bid (14,4) em comparação aos controles (1,0; p = 0,002). Leucócitos dos pacientes mostraram aumento de A1 (7,41, p = 0,001) e expressão reduzida do Bax (0,19; p = 0,04) e Bad (0,2; p = 0,030). Não houve correlação entre percentagem de alelos JAK2 V617F mutados e expressão molecular. Pacientes com PV apresentaram alterações na expressão de moléculas Bcl-2 que podem interferir no controle da apoptose e contribuir para a patogênese da doença.

Comparison of different criteria for the diagnosis of primary myelofibrosis reveals limited clinical utility for measurement of serum lactate dehydrogenase.

Primary myelofibrosis shows histological and pathogenetic overlap with essential thrombocythemia and polycythemia vera. Several diagnostic classifications have been proposed for primary myelofibrosis, although little is known about their clinical utility. In a comparison of three recent classifications, overall concordance was 79%. Inclusion of raised serum lactate dehydrogenase categorized 9% of patients as primary myelofibrosis when other criteria were not met. Although mean serum lactate dehydrogenase levels were higher in patients with primary myelofibrosis, levels were also increased in the majority of patients with essential thrombocythemia or polycythemia vera, and significant overlap was observed. A positive correlation with higher leukocyte and platelet count, and disease duration in primary myelofibrosis, suggests that serum lactate dehydrogenase is a biomarker for disease bulk and/or cellular proliferation. In conclusion, raised lactate dehydrogenase lacks specificity for primary myelofibrosis, consistent with the concept of a phenotypic continuum between essential thrombocythemia, polycythemia vera and primary myelofibrosis.

Rethinking disease definitions and therapeutic strategies in essential thrombocythemia and polycythemia vera.

The seminal discovery of the JAK2V617F mutation, which is highly prevalent in Philadelphia-negative myeloproliferative disorders, now renamed neoplasms, triggered an almost unprecedented explosion of interest and data in the field. Descriptions of additional mutations in exon 12 of JAK2, at position 515 in MPL, and a number of other mutations at low frequency followed these discoveries. These advances in our understanding of molecular pathogenesis of these conditions coincided with the publication of results from two major clinical studies, ECLAP and PT-1, which contributed important clinical insights and facilitated significant correlative data collection. This article, focusing mainly upon essential thrombocythemia and polycythemia vera, reviews four major themes: the impact upon classification of these disorders considering a radical review of current terminology, and then three areas pertinent to clinical management: the indications for cytoreductive therapy in which the key targets are to reduce thrombohemorrhagic complications, relieve disease-related symptoms, and minimize the risk of transformation to secondary myeloid malignancy such as myelodysplasia, leukemia, and secondary myelofibrosis; and second reviewing current and, last, future therapeutic options, in particular interferon and JAK2 inhibitors.

JAK2(V617F) allele burden discriminates essential thrombocythemia from a subset of prefibrotic-stage primary myelofibrosis.

OBJECTIVE: Among Philadelphia chromosome-negative myeloproliferative neoplasms (Ph(-) MPN), essential thrombocythemia (ET) and the prefibrotic phase of primary myelofibrosis (PMF) represent two subtypes with considerable overlap. MATERIALS AND METHODS: In this study, histopathological classification of 490 MPN cases was correlated with the allelic burden of JAK2(V617F) and MPL(W515L). RESULTS: Ph(-) MPN entities largely overlap with regard to JAK2(V617F) and MPL(W515L) allele burden, but ET displayed mutant allele burden <50%. PMF with different stages of myelofibrosis all yielded similar JAK2(V617F) allele burden. At initial presentation one-quarter of prefibrotic PMF cases exhibited an allele burden exceeding 50% (38% median JAK2(V617F) alleles, n=102). In ET, its main differential diagnosis, not a single case was found with >40% JAK2(V617F) alleles (median, 24% JAK2(V617F) alleles; n=90; p<0.001). Increase in JAK2(V617F) alleles during follow-up could not be linked to fibrosis or blastic progression but was related to polycythemic transformation in ET. MPL(W515L) was found in 3% of ET and 8% of PMF, with a significantly higher percentage of mutated alleles in fibrotic than prefibrotic PMF (median, 78% MPL(W515L) alleles; p<0.05). CONCLUSION: Histopathological categories ET and prefibrotic PMF correlate with significant differences in mutant allelic burden of JAK2(V617F), but not of MPL(W515L) which, by contrast to JAK2(V617F), shows a higher percentage of mutated alleles in fibrotic than in prefibrotic cases. Thus, for Ph(-) MPN in which ET and prefibrotic PMF represent the most probable diagnoses, a JAK2(V617F) allele burden >50% favors a diagnosis of prefibrotic PMF.

The 2008 World Health Organization classification system for myeloproliferative neoplasms: order out of chaos.

The first formal classification of chronic myeloid neoplasms is credited to William Dameshek, who in 1951 described the concept of "myeloproliferative disorders (MPD)" by grouping together chronic myelogenous leukemia, polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The 2001 World Health Organization (WHO) classification of myeloid malignancies included these MPDs under the broader category of chronic myeloproliferative diseases (CMPD), which also included chronic neutrophilic leukemia, chronic eosinophilic leukemia/hypereosinophilic syndrome (CEL/HES), and "CMPD, unclassifiable." The revised 2008 WHO classification system featured the following changes: 1) the term "CMPD" was replaced by "myeloproliferative neoplasm (MPN)," 2) mast cell disease was formally included under the category of MPN, and 3) the subcategory of CEL/HES was reorganized into "CEL not otherwise specified (CEL-NOS)" and "myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB, and FGFR1"; CEL-NOS remained a subcategory of "MPN," whereas the latter neoplasms were now assigned a new category of their own. Furthermore, diagnostic criteria for PV, ET, and PMF were revised by incorporating recently described molecular markers (eg, JAK2 and MPL mutations) as well as underscoring the role of histology in differentiating reactive from clonal myeloproliferations. As a result, red cell mass measurement is no longer necessary for the diagnosis of PV, and ET can now be diagnosed at a lower platelet count threshold. The revised WHO document continues to promote the recognition of histologic categories as a necessary first step toward the genetic characterization of myeloid malignancies.

The classification and diagnosis of erythrocytosis.

An absolute erythrocytosis is present when the red cell mass is raised and the haematocrit is elevated above prescribed limits. Causes of an absolute erythrocytosis can be primary where there is an intrinsic problem in the bone marrow and secondary where there an event outside the bone marrow driving erythropoiesis. This can further be divided into congenital and acquired causes. There remain an unexplained group idiopathic erythrocytosis. Investigation commencing with thorough history taking and examination and then investigation depending on initial features is required. Clear simple criteria for polycythaemia vera are now defined. Those who do not fulfil these criteria require further investigation depending on the clinical scenario and initial results. The erythropoietin level provides some guidance as to the direction in which to proceed and the order and extent of investigation necessary in an individual patient. It should thus be possible to make an accurate diagnosis in the majority of patients.

Essential thrombocythemia, polycythemia vera, and myelofibrosis: current management and the prospect of targeted therapy.

The recent discovery of JAK2 and/or MPL mutations in polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) has had a major impact on how we diagnose and treat these disorders. For instance, the presence of a JAK2 mutation is now considered conditio sine qua non for the diagnosis of PV and the World Health Organization classification system has recently revised its diagnostic criteria for PV, ET, and PMF to include JAK2 and MPL mutations as clonal markers. From the standpoint of treatment, JAK-STAT is now identified as a legitimate target pathway for drug development in myeloproliferative neoplasms. Herein, I will first outline my views regarding current management in ET, PV, and PMF and then discuss emerging data on preclinical and clinical activity of anti-JAK2 small molecule drugs. Am. J. Hematol., 2008. (c) 2008 Wiley-Liss, Inc.

Bone marrow pathology in essential thrombocythemia: interobserver reliability and utility for identifying disease subtypes.

The role of histopathology in the diagnosis of essential thrombocythemia (ET) is controversial, and there has been little attempt to quantitate interobserver variability. Diagnostic bone marrow trephine biopsy specimens from 370 patients with ET by Polycythemia Vera Study Group (PVSG) criteria were assessed by 3 experienced hematopathologists for 16 different morphologic features and overall diagnosis according to the World Health Organization (WHO) classification. Our results show substantial interobserver variability, particularly for overall diagnosis and individual cellular characteristics such as megakaryocyte morphology. Reticulin grade was the dominant independent predictor of WHO diagnostic category for all 3 hematopathologists. Factor analysis identified 3 independent factors likely to reflect underlying biologic processes. One factor related to overall and lineage-specific cellularity and was significantly associated with JAK2 V617F status (P < .001), a second factor related to megakaryocyte clustering, and a third was associated with the fibrotic process. No differences could be discerned between patients labeled as having "prefibrotic myelofibrosis" or "true ET" in clinical and laboratory features at presentation, JAK2 status, survival, thrombosis, major hemorrhage, or myelofibrotic transformation. These results show that histologic criteria described in the WHO classification are difficult to apply reproducibly and question the validity of distinguishing true ET from prefibrotic myelofibrosis on the basis of subjective morphologic criteria. This study was registered at http://isrctn.org as #72251782 and at http://eudract.emea.europa.eu/ as #2004-000245-38.

Primary myelofibrosis (PMF), post polycythemia vera myelofibrosis (post-PV MF), post essential thrombocythemia myelofibrosis (post-ET MF), blast phase PMF (PMF-BP): Consensus on terminology by the international working group for myelofibrosis research and treatment (IWG-MRT).

The International Working Group for Myelofibrosis Research and Treatment (IWG-MRT) is comprised of hematologists, hematopathologists, and laboratory scientists and its main goal is to provide a forum for scientific exchange and collaboration. During its first general meeting in April 2006, the IWG-MRT established uniform treatment response criteria for chronic idiopathic myelofibrosis (CIMF); also known as agnogenic myeloid metaplasia (AMM), myelofibrosis with myeloid metaplasia (MMM), and many other names in the hematologic literature. This document summarizes the proceedings from the second meeting of the IWG-MRT, in November 2006, where the group discussed and agreed to standardize the nomenclature referring to CIMF: (i) the term primary myelofibrosis (PMF) was chosen over several other designations including CIMF, AMM, and MMM, (ii) myelofibrosis that develops in the setting of either polycythemia vera (PV) or essential thrombocythemia (ET) will be referred to as post-PV MF and post-ET MF, respectively, and (iii) "leukemic" transformation will be recognized as blast phase disease (PMF-BP, post-PV/ET MF in blast phase).