How common are myeloproliferative neoplasms? A systematic review and meta‐analysis

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of diseases including polycythemia vera (PV), essential thrombocythemia (ET), and primary(idiopathic) myelofibrosis (PMF). In this systematic review, we provide a comprehensive report on the incidence and prevalence of MPNs across the globe. Electronic databases (PubMed, EMBASE, MEDLINE, and Web of Science) were searched from their inception to August 2012 for articles reporting MPN incidence or prevalence rates. A random effects meta‐analysis was undertaken to produce combined incidence rates for PV, ET, and PMF. Both heterogeneity and small study bias were assessed. Thirty‐four studies were included. Reported annual incidence rates ranged from 0.01 to 2.61, 0.21 to 2.27, and 0.22 to 0.99 per 100,000 for PV, ET, and PMF, respectively. The combined annual incidence rates for PV, ET, and PMF were 0.84, 1.03, and 0.47 per 100,000. There was high heterogeneity across disease entities (I² 97.1–99.8%) and evidence of publication bias for ET and PMF (Egger test, P = 0.007 and P ≤ 0.001, respectively).The pooled incidence reflects the rarity of MPNs. The calculated pooled incidence rates do not reflect MPN incidence across the globe due to the high unexplained heterogeneity. Improved, widespread registration of MPNs would provide better information for global comparison of the incidence and prevalence of MPNs. Am. J. Hematol. 89:581–587, 2014. © 2014 Wiley Periodicals, Inc.     

Perspectives on chronic inflammation in essential thrombocythemia, polycythemia vera, and myelofibrosis: is chronic inflammation a trigger and driver of clonal evolution and development of accelerated atherosclerosis and second cancer?

The morbidity and mortality of patients with the chronic Philadelphia-negative myeloproliferative neoplasms (MPNs), essential thrombocythemia, polycythemia vera, and primary myelofibrosis are mainly caused by cardiovascular diseases, thrombohemorrhagic complications, and bone marrow failure because of myelofibrosis and leukemic transformation. In the general population, chronic inflammation is considered of major importance for the development of atherosclerosis and cancer. MPNs are characterized by a state of chronic inflammation, which is proposed to be the common denominator for the development of "premature atherosclerosis," clonal evolution, and second cancer in patients with MPNs. Chronic inflammation may both initiate clonal evolution and catalyze its expansion from early disease stage to the myelofibrotic burnt-out phase. Furthermore, chronic inflammation may also add to the severity of cardiovascular disease burden by accelerating the development of atherosclerosis, which is well described and recognized in other chronic inflammatory diseases. A link between chronic inflammation, atherosclerosis, and second cancer in MPNs favors early intervention at the time of diagnosis (statins and interferon-α2), the aims being to dampen chronic inflammation and clonal evolution and thereby also diminish concurrent disease-mediated chronic inflammation and its consequences (accelerated atherosclerosis and second cancer).     

Molecular aspects of myeloproliferative neoplasms

During these past 5 years several studies have provided major genetic insights into the pathogenesis of the so-called classical myeloproliferative neoplasms (MPNs): polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The discovery of the JAK2V617F mutation first, then of the JAK2 exon 12 and MPLW515 mutations, have modified the understanding of these diseases, their diagnosis, and management. Now it is established that almost 100% of PV patients present a JAK2 mutation. Nearly 60% of ET patients and 50% of patients with PMF have the JAK2V617F mutation. The MPLW515 mutations are also present in a small proportion of ET and PMF patients. These mutations are oncogenic events that cause these disorders; however, they do not explain the heterogeneity of the entities in which they occur. Genetic defects have not been yet identified in around 40% of ET and PMF. There are likely additional somatic genetic factors important for the MPN phenotype like the recently described TET2, ASXL1, and CBL mutations. Moreover, polymorphisms in the JAK2 gene have been recently described as associated with MPN. Additional studies of large cohorts are required to dissect the genetic events in MPNs and the mechanisms of these oncogenic cooperations.     

A rapid,highly accurate method for quantifying CALR mutant allele burden in persons with myeloproliferative neoplasms

Abstract

Background

Calreticulin (CALR) mutations were recently identified in a substantial proportion of persons with essential thrombocythemia (ET) and with primary myelofibrosis (PMF) without JAK2^V617F. Consequently rapid, sensitive, and specific methods to detect and quantify these mutations are needed.

Methods

We studied samples from 1088 persons with myeloproliferative neoplasms (MPNs) including 421 JAK2^V617F negative subjects with ET, PMF, polycythemia vera (PV), chronic myeloid leukemia (CML) and hyper-eosinophilic syndrome (HES). Detection of CALR exon 9 mutations was done by PCR amplification followed by fragment length analysis and direct sequencing. Dilution assays were used to determine CALR mutant allele burden.

Results

We detected CALR mutations in blood and bone marrow samples from 152 subjects with ET and with PMF but not in samples from normal or persons with PV, CML, or HES. CALR mutant peaks were distinct from wild-type peaks and dilution experiments indicated a sensitivity level of 0.5–5% for a CALR mutant allele in a wild-type background. Diverse types of mutations were detected including deletions, insertions, and complex indels. All mutations were confirmed by direct sequencing. We also used dilution experiments to quantify mutant allele burden. We were able to reproducibly detect mutant allele levels as low 5% (0.5–5%) in a wild-type background.

Conclusions

PCR amplification followed by fragment length analysis is a rapid, sensitive, and specific method for screening persons with MPNs for CALR mutations, especially those with ET and PMF and for estimating mutant allele burden.     

JAK2V617F allele burden in patients with myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal malignant diseases that represent a group of conditions including polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). The JAK2-V617F mutation is prevalent in almost all patients with MPNs and has become a valuable biomarker for diagnosis of MPNs. A different allele burden in these entities has long been noticed. The aim of our study was to assess the JAK2 allele burden in our JAK2V617F positive cases and its association with phenotype if any and to select a simple, sensitive assay for use in our clinical molecular diagnostic laboratory. Methodologies reported in this literature include amplification refractory mutation system–polymerase chain reaction (ARMS-PCR) and real-time quantitative polymerase chain reaction (RQ-PCR). We analyzed 174 cases by RQ-PCR for the quantification of JAK2V617F were initially screened by ARMS-PCR. We found that V617F allele burden in the entire population of patients was 73 % ranging from 0.97 to 95 %. The median V617F allele burden in PV patients was 40 %, MF was 95 %, and ET was 25 %. ARMS-PCR and RQ-PCR were proven to be sensitive since ARMS-PCR is a qualitative method; it can be used to screen JAK2V617F mutation and RQ-PCR was used to quantify the V617F cells. Our study suggests that JAK2V617F positivity is associated with MPNs, and its allele burden is an excellent diagnostic marker for disease subtypes, prognosis, disease phenotype and complication, and evolution. The data indicates that ARMS-PCR is simple and can be easily performed for the primary screening of JAK2V617F mutation, and RQ-PCR is sensitive enough to detect low mutant allele levels (>10 %), specific enough not to produce false positive results, and can be performed for the JAK2V617F allele burden quantification.     

A case of myeloid sarcoma with correlation to JAK2V617F mutation, complicated by myelofibrosis and secondary acute myeloid leukemia

The activating mutation of JAK2, V617F, has been found as a frequent mutation in myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocytosis (ET), and primary myelofibrosis (PMF). This mutation is observed not only in MPNs, but also in chronic myelomonocytic leukemia, myelodysplastic syndrome and acute myeloid leukemia (AML). We report a case of myeloid sarcoma and myelofibrosis, followed by secondary AML, with detection of homozygous JAK2 V617F mutation. This report describes the first case of myeloid sarcoma with JAK2 V617F mutation and implication of its progression to AML.     

Classification and diagnosis of myeloproliferative neoplasms according to the 2008 World Health Organization criteria

The myeloproliferative neoplasms (MPNs) were first recognized by William Dameshek in 1951. The classic MPNs were polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF) and chronic myelogenous leukemia. They were originally grouped together based on their shared phenotype of myeloproliferation. Since then, important discoveries have been made, identifying a central role of protein tyrosine kinases in the pathogenesis of these disorders. As such, the 2008 WHO diagnostic classification for myeloproliferative neoplasms has incorporated molecular markers with histologic, clinical and laboratory information into the diagnostic algorithms for the MPNs. Important changes include (1) the change of nomenclature of myeloproliferative disorder to myeloproliferative neoplasm emphasizing the clonal nature of these disorders; (2) the classification of mast cell disease as an MPN; (3) the reorganization of the eosinophilic disorders into a molecularly defined category of PDGFRA, PDGFRB and FGFR1-associated myeloid and lymphoid neoplasms with eosinophilia and chronic eosinophilic leukemia, not otherwise specified; and (4) refinement of the diagnostic criteria for PV, ET and PMF incorporating recently described molecular markers, JAK2V617F, JAK2 exon 12 mutations and MPL mutations. This review focuses upon the important changes of the 2008 WHO diagnostic criteria for MPNs.     

MicroRNAs in myeloproliferative neoplasms

The chronic myeloproliferative neoplasms (MPN), including polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF), are clonal stem cell disorders characterized by dysregulated haematopoietic stem cell expansion and production of red cells, white cells and platelets alone or in combination. An acquired mutation JAK2^V617F can be found in all three disorders and shows many of the phenotypic abnormalities of the diseases in murine models. The disease phenotype is also influenced by other unknown genetic or epigenetic factors. MicroRNAs (miRNA) are 18–24 nucleotide single‐stranded non‐protein‐coding RNAs that function primarily as gene repressors by binding to their target messenger RNAs. There is growing evidence that miRNAs regulate haematopoiesis in both haematopoietic stem cells and committed progenitor cells. Here, we review the field of miRNA biology and its regulatory roles in normal haematopoiesis with an emphasis on miRNA deregulations in MPNs. Continued research into how miRNAs impact JAK2^V617F clonal expansion, differential haematopoiesis among different MPNs, disease progression and leukaemia transformation will lead to a better understanding of the development of these disorders, their clinical manifestations, and their treatment.     

How we manage Philadelphia-negative myeloproliferative neoplasms in pregnancy

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

Bone marrow microvessel density in chronic myeloproliferative disorders: a study of 115 patients with clinicopathological and molecular correlations

Philadelphia-negative chronic myeloproliferative disorders (CMD) include polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). Angiogenesis is critical in the pathogenesis of PMF. We studied angiogenesis in 115 patients with CMD (23 PV, 24 ET, 46 PMF, 12 post-PV and 10 post-ET myelofibrosis) by assessment of microvessel density (MVD) in bone marrow (BM). Kruskall–Wallis analysis of variance showed that patients with PMF had significantly higher values of MVD than those with PV ( P  <   0·001), ET ( P  <   0·001) and controls ( P  <   0·001). Mann–Whitney U -test demonstrated that patients with PMF at the prefibrotic stage had significantly higher MVD values than those with ET ( P  =   0·02). Patients with post-PV myelofibrosis showed significantly higher MVD values than those with PV ( P  <   0·001), as did patients with post-ET myelofibrosis compared with ET ( P  <   0·001). In patients with CMD, the multivariate generalized linear regression model showed that the JAK2 (V617F) mutational burden ( P  =   0·01), serum lactate dehydrogenase level ( P  =   0·003), and anaemia ( P  <   0·001) independently correlated with MVD. In summary, this study indicates that assessment of BM angiogenesis, as measured by MVD, may be a useful additional tool in the histopathological definition of CMD.     

Long term follow up of 93 families with myeloproliferative neoplasms: life expectancy and implications of JAK2V617F in the occurrence of complications

The long-term evolution of familial myeloproliferative neoplasms was studied in 93 families with 227 subjects including 97 with polycythemia vera (PV), 105 essential thrombocythemia (ET), 14 primary myelofibrosis (PMF) and 11 chronic myeloid leukemia (CML). In PV patients, with 12years of median follow-up, overall survival was 83% at 10years and 37% at 20years. A high JAK2(V617F) allele burden was correlated with the transformation to myelofibrosis (p<0.0001), but not with the transformation to acute leukemia. Among the 105 ET, with 8years of median follow-up, overall survival was 83% at 10years and 57% at 20years. Progression to acute leukemia and progression to myelofibrosis were 10% and 13%. There was a trend toward a more frequent evolution to myelofibrosis when the JAK2(V617F) mutated allele burden was >50% (p=0.09), but not to AML. Hematologic transformation of the MPN was responsible for 69% of the deaths, cerebral stroke for 7% and 4% died of myocardial infarction. Eleven JAK2(V617F) mutated patients developed 13 deep splanchnic thromboses in PV and ET. Finally whereas patients with familial PV and ET have a comparable prognosis to non-familial MPN, the JAK2(V617F) mutation was associated with a more frequent occurrence of thrombosis in the entire population.     

JAK2 inhibitors: What's the true therapeutic potential?

Physicians treating patients with the classic Philadelphia-negative myeloproliferative neoplasms (Ph-negative MPNs) (polycythemia vera [PV], essential thrombocythemia [ET] and primary myelofibrosis [PMF]) traditionally had few therapeutic drugs available. Spurred by the discovery of activating mutation of the JAK2 tyrosine kinase (JAK2 V617F mutation) in patients with Ph-negative MPNs several years ago, several JAK2 inhibitors were synthesized and are currently undergoing clinical trials in patients with PMF, PV and ET. Initial results from these studies have shown that these drugs can markedly reduce spleen size and alleviate constitutional symptoms, increase weight and improve exercise capacity in MF patients, thus improve quality of their life, which is significant clinical benefit. In ET and PV JAK2 inhibitor therapy may efficiently control blood cell count, as well as improve splenomegaly and control disease related symptoms. JAK2 inhibitors are a novel class of agents with promising results for treating patients with MF, PV and ET. In this article we will review the current evidence regarding the role of JAK2 mutations in the pathogenesis of Ph-negative MPNs and summarize results from the most recent clinical trials with JAK2 inhibitors in these disorders. JAK2 inhibitors are a novel class of agents with promising results for treating patients with MF, PV and ET.     

The expression of lysyl‐oxidase gene family members in myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are malignant disorders originating from clonal expansion of a single neoplastic stem cell and characteristically show an increase in bone marrow reticulin fibers. Lysyl oxidases (LOXs) are copper‐dependent amine oxidases that play a critical role in the biogenesis of connective tissue by crosslinking extracellular matrix proteins, collagen and elastin. Expression of LOX gene family members is increased in disorders associated with increased fibrosis. To evaluate involvement of LOX gene family in various MPNs. In‐situ hybridization was used to detect Lysyl‐Oxidase family members in bone marrow biopsies from patients with different MPNs. We compared normal bone marrows and those from patients with polycythemia vera, essential thrombocythemia, chronic myeloid leukemia, and primary myelofibrosis (PMF). Serum levels of lysyl‐oxidase from patients with PMF and healthy controls were also examined. LOX gene family was not detected in normal bone marrows. All members of the LOX gene family were over expressed in PMF. In other MPNs a differential pattern of expression was observed. Differences in gene expression were statistically significant (P < 0.010). The medianserum LOX levels in normal controls was 28.4 ± 2.5 ng\ml and 44.6 ± 9.44 ng\ml in PMF (P = 0.02). The varying pattern of expression of LOX genes may reflect differences in the pathophysiology of bone marrow fibrosis in these MPNs. These observations could be used as the basis for future targeted therapy directed against bone marrow fibrosis. Am. J. Hematol. 88:355–358, 2013. © 2013 Wiley Periodicals, Inc.     

JAK2 46/1 haplotype is associated with JAK2 V617F-positive myeloproliferative neoplasms in Japanese patients

Myeloproliferative neoplasms (MPNs) constitute a group of phenotypically diverse chronic myeloid malignancies, characterized by clonal hematopoiesis and excessive production of terminally differentiated myeloid blood cells. The MPNs include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), most of which are characterized by a somatic point mutation, V617F, in the janus kinase 2 (JAK2) gene. This mutation was recently shown to occur more frequently in a specific JAK2 haplotype, JAK2 46/1, in North American and European MPN patients. Little is known, however, about JAK2 haplotypes in Japanese MPN patients. Therefore, we examined 108 Japanese patients with MPN, including 19 with PV, 61 with ET, 10 with PMF, and 17 with unclassifiable MPN, as well as 104 control individuals for the JAK2 rs10974944(C/G) single nucleotide polymorphism, in which the G allele indicates the 46/1 haplotype. We found that the JAK2 46/1 haplotype was significantly more frequent in patients with V617F-positive MPN than in controls (odds ratio [OR], 3.6; 95 % confidence interval [CI], 2.2–5.8, p < 0.001), and in PV patients than in controls (OR, 6.3; 95 % CI, 3.0–29.4, p < 0.001). In conclusion, we demonstrated that the JAK2 46/1 haplotype is associated with JAK2 V617F-positive MPNs in Japanese patients.     

The JAK2 V617F allele burden in essential thrombocythemia, polycythemia vera and primary myelofibrosis--impact on disease phenotype

Background and objectives: The JAK2 V617F tyrosine kinase mutation is present in the great majority of patients with polycythemia vera (PV), and approximately half of the patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF). The three distinct disease entities may be considered as three phenotypic presentations of the same JAK2 V617F positive chronic myleoproliferative disorder. Together with physiological and genetic modifiers the phenotype may be determined by the JAK2 V617F allele burden. In the present study, we aimed to asses the JAK2 mutational load and its impact on phenotype. Methods: A highly sensitive real‐time quantitative PCR (qPCR) assay was used for quantification of the JAK2 V617F mutational load in 165 patients with Philadelphia chromosome negative chronic myeloproliferative disorders (ET = 40, PV = 95, PMF = 30). Results: We provide evidence of increasing JAK2 V617F allele burden from ET, over PV to PMF (P = 0.001 and P < 0.00001 respectively). The present data suggests the JAK2 V617F allele burden as a key determinant of the degree of myeloproliferation and myeloid metaplasia reflected by significantly higher levels of white blood cell counts (WBC) (P = 0.03), CD34 counts (P = 0.03), lactate dehydrogenase and Polycythemia Rubra Vera gene 1 levels (P = 0.03 and P < 0.00001 respectively), as well as lower platelet counts (P = 0.02) and more cases of splenomegaly (P = 0.001) in homozygous PV patients compared to their heterozygous counterparts. Conclusion: The present study support the concept of the JAK2 V617F positive chronic myeloproliferative disorders as a biological continuum with phenotypic presentation in part influenced by JAK2 V617F mutational load.     

WHO‐histological criteria for myeloproliferative neoplasms: reproducibility,diagnostic accuracy and correlation with gene mutations and clinical outcomes

Bone marrow histology is included in the diagnostic criteria of myeloproliferative neoplasms (MPNs). However, some concerns have emerged about its reproducibility. To evaluate the diagnostic accuracy of histology and to assess its correlation with presence of mutations and clinical outcomes, two pathologists reviewed the bone marrow biopsies corresponding to 211 patients with MPN. Despite the low agreement in the evaluation of individual histopathological characteristics, the concordance among pathologists when establishing the diagnosis was good (Kappa index 0·67). The specificity of histology was 100%, 98·5% and 98% in polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF), respectively, whereas the sensitivity of histological diagnosis was low in PV and ET (32·5% and 54% respectively) and acceptable in PMF (75%). Thirteen out of 146 (9%) patients with clinical ET were diagnosed as prefibrotic PMF. No histological agreement or MPN otherwise unspecified was more frequently observed in JAK2 V617F‐positive ET than in CALR‐mutated cases, whereas megakaryocytic abnormalities and prefibrotic PMF were more frequently observed in CALR‐mutated ET. In conclusion, histological criteria of MPN have a limited diagnostic accuracy due to low sensitivity. Patients with JAK2 V617F‐positive MPN have a heterogeneous histology while CALR‐positive ET is associated with megakaryocyte abnormalities and prefibrotic PMF.     

Dysregulation of the MIRLET7/HMGA2 axis with methylation of the CDKN2A promoter in myeloproliferative neoplasms

Overexpression of high mobility group AT‐hook 2 (Hmga2), which is negatively regulated by MIRLET7 micro RNAs through 3′‐untranslated region (3′UTR), causes proliferative haematopoiesis mimicking myeloproliferative neoplasms (MPNs) and contributes to progression of myelofibrosis in mice. Thus, we investigated HMGA2 mRNA expression in 66 patients with MPNs including 23 polycythaemia vera (PV), 33 essential thrombocythaemia (ET) and 10 primary myelofibrosis (PMF). HMGA2 mRNA expression, especially variant 1 with 3′UTR that contains MIRLET7‐specific sites, rather than variant 2 lacking 3′UTR, is frequently deregulated due to decreased MIRLET7 expression in granulocytes from over 20% of PV and ET, and in either granulocytes or CD34⁺ cells from 100% of PMF. Patients with deregulated HMGA2 mRNA expression were significantly more likely to show splenomegaly, high serum lactate dehydrogenase values, and methylation of the CDKN2A promoter compared with other patients without deregulation of HMGA2. A histone deacetylase inhibitor, panobinostat, significantly increased MIRLET7 expression and reduced variant 1 of HMGA2 mRNA expression, but not variant 2, in both U937 cells and PMF‐derived CD34⁺ cells. Moreover, both panobinostat and small interfering RNA of HMGA2 demethylated the CDKN2A promoter in U937 cells. In conclusion, the frequently dysregulated MIRLET7/HMGA2 axis could be a therapeutic target in MPNs.     

Application of an NGS‐based 28‐gene panel in myeloproliferative neoplasms reveals distinct mutation patterns in essential thrombocythaemia,primary myelofibrosis and polycythaemia vera

Molecular routine diagnostics for BCR‐ABL1‐negative myeloproliferative neoplasms (MPN) currently focusses on mutations in JAK2, CALR and MPL. In recent years, recurrent mutations in MPNs have been identified in several other genes. We here present the validation of a next generation sequencing (NGS)‐based 28‐gene panel and its use in MPN. We analysed the mutation status of 28 genes in 100 MPN patients [40 essential thrombocythaemia (ET), 30 primary myelofibrosis (PMF), 30 polycythaemia vera (PV)] and found two or more mutated genes in 53 patients. Moreover, significantly more mutated splicing genes (SF3B1, SRSF2 and U2AF1) were present in PMF (0·60 mutated genes/patient) compared to ET (0·15) while no mutations in splicing genes were found in PV. Additionally, chromatin modification genes (ASXL1 and EZH2) were frequently mutated in PMF patients (0·50) and, to a significantly lesser extent, in ET (0·13) and PV (0·07). Contrarily, DNA methylation genes (DNMT3A, IDH1, IDH2 and TET2) were mutated most often in PV (0·5) and less frequently in ET (0·23) and PMF (0·20), but without reaching statistical significance. Our results demonstrate the feasibility and utility of NGS‐based panel diagnostics for MPN. With 53% of the patients bearing two or more mutated genes, their prognostic relevance needs further studies.