Essential thrombocythemia

Philadelphia chromosome-negative myeloproliferative neoplasms in younger adults: A critical discussion of unmet medical needs, with a focus on pregnancy

Myeloproliferative neoplasms (MPN) are traditionally regarded as a disease of older adults, though a not negligible fraction of cases occurs at a younger age, including women of childbearing potential. MPN in younger patients, indeed, offer several challenges for the clinical hematologist, that goes from difficulties in reaching a timely and accurate diagnosis to a peculiar thrombotic risk, with a relatively high incidence of thromboses in unusual sites (as the splanchnic veins or the cerebral ones). Moreover, the issue of pregnancy is recently gaining more attention as maternal age is rising and molecular screening are widely implemented, leading to a better recognition of these cases, both before and during pregnancy. In the present work we aim at discussing four clinical topic that we identified as areas of uncertainty or true unmet medical needs in the management of younger patients with MPN, with a particular focus on the topic of pregnancy. For each of these topics, we critically reviewed the available evidence that support treatment decisions, though acknowledging that recommendations in this field are mostly based on expert opinion or derived from guidelines of other clinical conditions that share with MPN a high vascular risk, as antiphospholipid syndrome. Taking into consideration both the lack of evidence-based data and the clinical heterogeneity of MPN, we support an individualized strategy of counseling and management for both young patients and for expectant mother with MPN.

Sequential Development of JAK2V617F Mutation and BCR-ABL1 Fusion in Individual Patients With Myeloproliferative Neoplasms: A Linear Clonal Evolution or Parallel Clonal Competition?

CONTEXT.—

Concomitant BCR-ABL1 and JAK2V617F in myeloproliferative neoplasms (MPNs) is rare, and its pathogenesis and clinical significance are unclear.

OBJECTIVE.—

To investigate the clonal relationship between the 2 genomic alterations, as well as the clinicopathologic impact.

DESIGN.—

Retrospective analysis of MPNs with sequential development of BCR-ABL1 and JAK2V617F.

RESULTS.—

Of 6 cases, 5 had JAK2V617F-positive MPN diagnosed before acquiring BCR-ABL1 years later, and 1 had BCR-ABL1+ chronic myeloid leukemia before JAK2V617F-positive myelofibrosis completely replaced the BCR-ABL1+ clone 1 year after tyrosine kinase inhibitor therapy. Among the former group, treatment for the initial MPN involved hydroxyurea, ruxolitinib, and/or supportive care, and the latency to the development of JAK2V617F ranged from 4 to 13 years (median of 9 years). Four cases showed retention of JAK2V617F, whereas BCR-ABL1 emerged as the major clone, including 2 that exhibited parallel increases in JAK2V617F and BCR-ABL1 burdens, with both genomic markers exceeding 50%. Three patients received stem cell transplants and demonstrated sustained engraftment, with the genomic markers below detectable levels.

CONCLUSIONS.—

Most MPNs with concomitant JAK2V617F and BCR-ABL1 are actually composite MPNs with a "second hit" residing on a different clone. Rare cases demonstrate a subclone harboring a "double-hit" in a background of a JAK2V617F-positive stem line clone. The probability of a "double-hit" with a BCR-ABL1+ stem line clone is probably reduced by effective tyrosine kinase inhibitor treatment. The treatment often involves combined kinase inhibitors and/or hydroxyurea, but the outcome is unpredictable; hematopoietic stem cell transplantation may be the ultimate therapeutic option for this complicated disease.

Synoptic Diagnostics of Myeloproliferative Neoplasms: Morphology and Molecular Genetics

Simple Summary

The diagnosis of myeloproliferative neoplasms requires assessment of a combination of clinical, morphological, immunophenotypic and genetic features, and this integrated, multimodal approach forms the basis for precise classification. Evaluation includes cell counts and morphology in the peripheral blood, bone marrow aspiration and trephine biopsy, and may encompass flow cytometry for specific questions. Diagnosis nowadays is completed by targeted molecular analysis for the detection of recurrent driver and, optionally, disease-modifying mutations. According to the current World Health Organization classification, all myeloproliferative disorders require assessment of molecular features to support the diagnosis or confirm a molecularly defined entity. This requires a structured molecular analysis workflow tailored for a rapid and cost-effective diagnosis. The review focuses on the morphological and molecular features of Ph-negative myeloproliferative neoplasms and their differential diagnoses, addresses open questions of classification, and emphasizes the enduring role of histopathological assessment in the molecular era.

Abstract

The diagnosis of a myeloid neoplasm relies on a combination of clinical, morphological, immunophenotypic and genetic features, and an integrated, multimodality approach is needed for precise classification. The basic diagnostics of myeloid neoplasms still rely on cell counts and morphology of peripheral blood and bone marrow aspirate, flow cytometry, cytogenetics and bone marrow trephine biopsy, but particularly in the setting of Ph− myeloproliferative neoplasms (MPN), the trephine biopsy has a crucial role. Nowadays, molecular studies are of great importance in confirming or refining a diagnosis and providing prognostic information. All myeloid neoplasms of chronic evolution included in this review, nowadays feature the presence or absence of specific genetic markers in their diagnostic criteria according to the current WHO classification, underlining the importance of molecular studies. Crucial differential diagnoses of Ph− MPN are the category of myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement of PDGFRA, PDGFRB or FGFR1, or with PCM1-JAK2, and myelodysplastic/myeloproliferative neoplasms (MDS/MPN). This review focuses on morphological, immunophenotypical and molecular features of BCR-ABL1-negative MPN and their differential diagnoses. Furthermore, areas of difficulties and open questions in their classification are addressed, and the persistent role of morphology in the area of molecular medicine is discussed.

Anagrelide in Essential Thrombocythemia (ET): Results from 150 patients over 25 years by the "Ph1-negative Myeloproliferative Neoplasms Latium Group"

BACKGROUND AND AIMS

Anagrelide is a drug effective in reducing platelet counts in essential thrombocythemia (ET) and Ph1-negative myeloproliferative neoplasms. The aim of this study was to evaluate the real-life use of anagrelide in patients with ET followed over 25 years at the Haematological Institutes belonging to "Ph1-negative Myeloproliferative Neoplasms Latium Group."

PATIENTS AND METHODS

Eligibility criteria were diagnosis of ET and treatment with anagrelide. Data were collected through an ad hoc case report form.

RESULTS

One hundred and fifty patients received anagrelide for a median time of 7.4 years (0.1-23.2). Anagrelide was administered as first-line therapy in 34.7% of patients, as second-line in 52% and as third-line in 13.3%: 85.4% responded to therapy. Sixty-eight/136 evaluable patients reported side effects: palpitations, peripheral vasodilation, anaemia, diarrhoea and gastric distress. Fourteen thrombotic (arterial 10, venous 4) and 51 bleeding events (minor 48, major 3) occurred. Sixteen/150 (10.6%) patients developed secondary myelofibrosis and 3/150 (2%) an acute myeloid leukaemia.

CONCLUSIONS

In our experience, anagrelide is an effective drug in reducing platelet levels in a high percentage of patients with ET. It is especially addressed to younger people. A careful assessment of the thrombotic risk and monitoring of cardiac function, at diagnosis and during follow-up, is mandatory.

Association of Treatments for Myeloproliferative Neoplasms During Pregnancy With Birth Rates and Maternal Outcomes: A Systematic Review and Meta-analysis

Importance

Myeloproliferative neoplasms (MPNs) are increasingly being identified in women of childbearing potential. Pregnancy in women with MPNs is associated with maternal thrombosis, hemorrhage, and placental dysfunction leading to fetal growth restriction or loss.

Objective

To evaluate the association between the use of aspirin, heparin, interferon, or combinations and live birth rate and adverse maternal outcomes in pregnant women with MPNs.

Data Sources

Systematic searches of MEDLINE, Embase, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, and the MEDLINE Epub Ahead of Print and In-Process and Other Non-Indexed Citations from inception to July 19, 2018, with no language restrictions, was conducted. Key search terms included myeloproliferative disorders, polycythemia vera, essential thrombocythemia, and primary myelofibrosis.

Study Selection

A study was eligible if it included pregnant patients with MPNs; interventions included aspirin, heparin, and/or interferon; there was a comparison group in which patients did not receive the intervention; the study reported on at least 1 of the study outcomes; and it was a randomized, case-control, or cohort study or series of at least 10 pregnancies. Data were extracted in duplicate; 0.5% of identified studies met selection criteria.

Data Extraction and Synthesis

The review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and reported in accordance with Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. Data were pooled using the Mantel-Haenszel approach.

Main Outcomes and Measures

Outcomes were the number of live births and maternal complications, specifically, arterial or venous thrombosis, hemorrhage, and preeclampsia.

Results

Twenty-two studies reporting on 1210 pregnancies were included. The live birth rate was 71.3% (95% CI, 65.1%-77.6%). Use of aspirin (11 studies, 227 patients; unadjusted odds ratio, 8.6; 95% CI, 4.0-18.1) and interferon (6 studies, 90 patients; unadjusted odds ratio, 9.7; 95% CI, 2.3-41.0) were associated with higher odds of live birth. Addition of heparin to aspirin was not associated with higher odds of live birth (6 studies, 96 patients; unadjusted odds ratio, 2.1; 95% CI, 0.5-9.0). The most common adverse maternal event was preeclampsia, with an incidence of 3.1% (95% CI, 1.7%-4.5%).

Conclusions and Relevance

Most studies reported on pregnancy with essential thrombocythemia. Few studies reported on pregnancy with polycythemia vera and none with myelofibrosis met the inclusion criteria. Most studies were retrospective and early pregnancy losses may have been underreported. Moderate-quality evidence suggests that aspirin or interferon is associated with higher odds of live birth in pregnant women with MPN.

Contemporary management of patients with BCR-ABL1-negative myeloproliferative neoplasms during pregnancy

INTRODUCTION

The management of pregnancy during the course of BCR-ABL1-negative myeloproliferative neoplasms (MPN) is an increasingly relevant problem. This is mostly due to earlier and better diagnosis of MPN together with the trend in modern society toward delaying pregnancy until later life. Areas Covered: The present review aims to provide an overview of the available literature data concerning outcome of pregnancy in MPN. Possible therapeutic modalities are discussed and a management algorithm is suggested. Expert Commentary: Most data are available for women with essential thrombocythemia and we present 793 published pregnancies. Live birth rate is 68.5% with 31.5% miscarriages. Spontaneous abortion is the most frequent complication with 26.5%, followed by stillbirth with 4.8%. Maternal complications are relatively low with 1.8% major thrombotic and 2.4% major bleeding events. In polycythemia vera the situation is clinically more complex and roughly 150 pregnancy reports are available. There is very limited information in primary myelofibrosis with less than 20 reported pregnancies. With active management including control of blood counts, aspirin, low molecular weight heparin and in higher risk cases interferon alpha pregnancy in MPN is manageable with a success rate not far below the normal situation with 80%.

Pregnancy outcomes in myeloproliferative neoplasms: UK prospective cohort study

The reported higher risk of maternal and fetal complications in women with myeloproliferative neoplasms (MPN) poses challenge during pregnancy. A national prospective study of maternal and fetal outcomes of pregnant women with a diagnosis of MPN was undertaken via the United Kingdom Obstetric Surveillance System between January 2010 and December 2012. Fifty-eight women with a diagnosis of MPN were identified; 47 (81%) essential thrombocythaemia, five (9%) polycythaemia vera, five (9%) myelofibrosis and one (2%) MPN-unclassified. There were 58 live births. The incidence of miscarriage was 1·7/100 (95% confidence interval [CI]: 0·04-9·24) and the perinatal mortality rate was 17/1000 (95% CI: 0·44-92·36) live and stillbirths. Incidence of maternal complications was 9% (5/57) pre-eclampsia, 9% (5/57) post-partum haemorrhage and 3·5% (2/57) post-partum haematoma. There were no maternal deaths or thrombotic events. Delivery was induced in 45% (24/53) of women and the Caesarean section rate was 45% (24/53). The majority (85%, 45/53) delivered at term (>37 weeks gestation). Twenty-two percent (12/54) of neonates were below the 10% centile for growth and 13% (7/54) required admission to a neonatal care-unit; there were no neonatal deaths. The findings of this large, UK prospective study suggests women with MPN appear to have successful pregnancies with better outcomes than would be anticipated from the literature.

JAK2 mutants (e.g., JAK2V617F) and their importance as drug targets in myeloproliferative neoplasms

The Janus kinase 2 (JAK2) mutant V617F and other JAK mutants are found in patients with myeloproliferative neoplasms and leukemias. Due to their involvement in neoplasia and inflammatory disorders, Janus kinases are promising targets for kinase inhibitor therapy. Several small-molecule compounds are evaluated in clinical trials for myelofibrosis, and ruxolitinib (INCB018424, Jakafi®) was the first Janus kinase inhibitor to receive clinical approval. In this review we provide an overview of JAK2V617F signaling and its inhibition by small-molecule kinase inhibitors. In addition, myeloproliferative neoplasms are discussed regarding the role of JAK2V617F and other mutant proteins of possible relevance. We further give an overview about treatment options with special emphasis on possible combination therapies.

Platelet genetic biomarker quantification: comparison of fluorescent microspheres and PCR platforms

The platelet transcriptome has been extensively characterised using distinct genetic profiling platforms, with evolving evidence for differential expression patterns between healthy individuals and subject cohorts with various haematologic and cardiovascular disorders. Traditional technological platforms for platelet genetic biomarker quantification have limited applicability for clinical molecular diagnostics due to inherent complexities related to RNA isolation and analysis. We have previously established the feasibility of fluorescent microspheres as a simple and reproducible strategy for simultaneous quantification of platelet mRNAs from small volume of blood using intact platelets. We now extend these observations by formally comparing in a 50-member normal cohort the cross-platform behaviour of fluorescent microspheres to the currently accepted Q-PCR standard, using a clinically relevant 15-biomarker gene subset able to discriminate among normal and thrombocytosis cohorts. When compared to Q-PCR, genetic biomarker quantification using fluorescent microspheres demonstrated lower coefficients of variation for low-abundant transcripts, better linearity in serially diluted samples, and good overall between-platform consistency via the geometric mean regression. Neither platform demonstrated age or gender effects for any of the 15 biomarkers studied. Binding site saturation for highly abundant transcripts using fluorescent microspheres can be readily eliminated using an optimal platelet number corresponding to 0.3 ml of peripheral blood, additionally applicable to thrombocytopenic cohorts. These data provide a detailed cross-platform analysis using a relevant biomarker subset, further highlighting the applicability of fluorescent microspheres as potentially superior to Q-PCR for platelet mRNA diagnostics.

Class prediction models of thrombocytosis using genetic biomarkers

Criteria for distinguishing among etiologies of thrombocytosis are limited in their capacity to delineate clonal (essential thrombocythemia [ET]) from nonclonal (reactive thrombocytosis [RT]) etiologies. We studied platelet transcript profiles of 126 subjects (48 controls, 38 RT, 40 ET [24 contained the JAK2V(617)F mutation]) to identify transcript subsets that segregated phenotypes. Cross-platform consistency was validated using quantitative real-time polymerase chain reaction (RT-PCR). Class prediction algorithms were developed to assign phenotypic class between the thrombocytosis cohorts, and by JAK2 genotype. Sex differences were rare in normal and ET cohorts (< 1% of genes) but were male-skewed for approximately 3% of RT genes. An 11-biomarker gene subset using the microarray data discriminated among the 3 cohorts with 86.3% accuracy, with 93.6% accuracy in 2-way class prediction (ET vs RT). Subsequent quantitative RT-PCR analysis established that these biomarkers were 87.1% accurate in prospective classification of a new cohort. A 4-biomarker gene subset predicted JAK2 wild-type ET in more than 85% patient samples using either microarray or RT-PCR profiling, with lower predictive capacity in JAK2V(617)F mutant ET patients. These results establish that distinct genetic biomarker subsets can predict thrombocytosis class using routine phlebotomy.

Philadelphia chromosome-negative chronic myeloproliferative disease

Session 2 of the 2007 Workshop of the Society for Hematopathology/European Association for Haematopathology was focused on Philadelphia chromosome-negative chronic myeloproliferative diseases (Ph- MPDs), recently termed chronic myeloproliferative neoplasms. The presented and submitted cases highlighted some important issues and also impending problems associated with the diagnosis and classification. Cases included predominantly rare entities like chronic eosinophilic leukemia and related disorders, chronic neutrophilic leukemia, and others with specific genetic abnormalities that allowed molecularly targeted therapy. In this context, the distinctive role of a positive JAK2(V617F) mutation for the diagnosis of Ph- MPD was underscored, including entities with a low allele burden and the discrimination from reactive disorders (autoimmune myelofibrosis, reactive thrombocytosis). Although novel genetic and molecular approaches have significantly improved the way we classify Ph- MPD, a combined clinicopathologic approach, including representative bone marrow specimens, still remains the yardstick for diagnosis.

Management of Philadelphia negative chronic myeloproliferative disorders in pregnancy

The management of pregnancy in Philadelphia negative chronic myeloproliferative disorders (CMPDs) is an increasingly frequent problem. In the literature, most pregnancies are reported for women with essential thrombocythemia (ET) with about 400 pregnancies in about 200 women. In ET, first trimester abortion is the most frequent complication occurring in about one third of pregnancies. Interestingly, the incidence of maternal complications is relatively low with 3% for major thromboembolic and 2% for major bleeding events. The presence of the Jak2 mutation seems to be an independent predictor of pregnancy complications. Pregnancies in ET should be stratified according to underlying risk factors in low, high and highest risk pregnancies. Women with low risk pregnancies are treated with low-dose aspirin, whereas women with high and higher risk pregnancies may benefit from low-dose aspirin plus interferon alpha +/- low molecular weight heparin throughout pregnancy and at least for six weeks post-partum. In polycythemia vera (PV) there is only very few information on pregnancy outcome with 36 pregnancies reported in the literature. According to these data pregnancy in PV is per se a high risk situation. Accordingly, all women with PV should be treated with low-dose aspirin. Some pregnant PV patients may benefit from a more intensive therapy including interferon alpha +/- low molecular weight heparin throughout pregnancy and at least for six weeks post-partum.

Low recurrence of preexisting extrahepatic malignancies after liver transplantation

The incidence of de novo malignancies is increased in organ transplant recipients, and patients with hepatic carcinomas are at high risk for tumor recurrence after liver transplantation. Data about recurrent cancer after orthotopic liver transplantation (OLT) in patients with a history of nonhepatic malignancy are very limited. We retrospectively analyzed data from 606 adult OLT recipients and identified 37 patients (6.1%) with a preexisting extrahepatic malignancy. In the same group, 43 patients (7.0%) developed de novo cancer. Preexisting malignancies included 26 solid tumors and 11 hematological malignancies, including 7 patients with Budd-Chiari syndrome due to myeloproliferative disorders (MPDs). Patients had been selected for OLT because of the expected good prognosis of their preexisting malignancy. Except for 3 patients, recipients were tumor-free at OLT. The median interval from tumor diagnosis to OLT was 44 months (range, <1-321). After a median follow-up of 66 months post transplantation (range, 4-131), all but 1 recipient with incidental colon carcinoma were free of recurrence. No patient with MPD showed leukemic transformation, whereas a patient with neurofibromatosis experienced growth of skin fibromas. Our data and an included review of published OLT recipients with preexisting malignancies have enabled us to show that recurrence rates are comparable for nontransplanted patients and renal-transplant recipients. In conclusion, cancer recurrence is low if OLT recipients are carefully selected. Therefore, previous extrahepatic malignancy should not be considered a contraindication for OLT per se, but the oncologic/hematologic prognosis should be considered, particularly with respect to the current 5-year survival rate of OLT.

The association of JAK2V617F mutation and leukocytosis with thrombotic events in essential thrombocythemia

OBJECTIVES

The Janus kinase 2 mutation, JAK2 (V617F), and megakaryocytic mutations, MPL (W515L/K), have been identified and correlated with a subtype of essential thrombocythemia (ET) patients. We investigated the frequency of mutations in ET patients and analyzed the relationship with their clinical features.

METHODS

Fifty-three ET patients were enrolled in the study. The amplification refractory mutation system was applied for the mutation survey of the JAK2V617F, while the polymerase chain reaction with sequencing was used for the mutation survey of MPLW515L/K.

RESULTS

Thirty-five (66%) patients harboring the JAK2 (V617F) mutation, including 3 homozygous and 32 heterozygous changes, but no MPLW515L/K mutation, were found. During follow-up, 17 (32.1%) patients suffered from documented thrombotic events, with 15 having JAK2V617F mutations. Statistical analysis showed that patients with the JAK2 mutation had significantly higher leukocytes, hemoglobin level, and thrombotic event (p = 0.043, p = 0.001, and p = 0.029, respectively). Thrombotic events were also significantly correlated with leukocytosis and older age.

CONCLUSIONS

The JAK2V617F mutation was noted in a certain population of ET patients and correlated with leukocytosis, high hemoglobin level, and thrombosis. Therefore, detection of the JAK2V617F mutation can affect not only the diagnosis, but also the management of ET patients.

JAK2V617F-negative ET patients do not display constitutively active JAK/STAT signaling

OBJECTIVE

Presence of the JAK2V617F mutation in only 40% to 60% of patients with essential thrombocythemia (ET) underscores the heterogeneity of this myeloproliferative disorder (MPD). Several distinct mutations, either in JAK2 (exon 12) or in c-Mpl (W515L) have been described in subsets of other MPDs, polycythemia vera, and idiopathic myelofibrosis. Analogous to JAK2,V617F these mutations cause constitutive JAK2 and signal transducer and activation of transcription (STAT) activation. It has therefore been proposed that constitutive activation of the JAK/STAT pathway underlies the molecular etiology of all MPDs. We investigated the alternative hypothesis that distinct alterations, separate from the JAK/STAT signal transduction pathway, underlie a subset of JAK2V617F-negative ET.

METHODS

cDNA microarrays and quantitative reverse transcriptase polymerase chain reactions were used to compare gene expression in 40 ET patients with and without the JAK2V617F mutation.

RESULTS

Unsupervised clustering of gene-expression patterns in ET patients revealed two distinct subclasses of patients. These subclasses differed in presence or absence of the JAK2V617F mutation. Patients lacking the JAK2V617F mutation displayed significantly lower expression of the JAK/STAT target genes Pim-1 and suppressor of cytokine signaling-2. In addition, JAK2V617F-negative patients showed lower levels of STAT3 phosphorylation.

CONCLUSIONS

These data demonstrate that a large proportion of JAK2V617F-negative ET patients do not display constitutive JAK/STAT signaling. Hence, we propose that alterations in different signal transduction pathways can lead to the clinical phenotype of ET. Elucidation of novel ET-inducing changes will facilitate both a molecular classification of ET and development of rationally designed therapies.

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

OBJECTIVE

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

METHODS AND RESULTS

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

CONCLUSION

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

Clinical features of polycythemia vera and essential thrombocythemia in Japan: retrospective analysis of a nationwide survey by the Japanese Elderly Leukemia and Lymphoma Study Group

We conducted the first nationwide survey to clarify the clinical features, treatment methods, and prognoses for polycythemia vera (PV) and essential thrombocythemia (ET). A 1-page questionnaire was mailed to members of the Japanese Elderly Leukemia and Lymphoma Study Group (JELLSG). Surveys on 647 patients (PV, 266 patients; ET, 381 patients) were returned and analyzed. Thrombotic events at diagnosis and during follow-up occurred at rates of 15.4% and 8.5%, respectively, in PV cases and 17.6% and 8.7% in ET cases. Splenomegaly was observed in only 28.8% of PV patients and 10.8% of ET patients. The leukocyte alkaline phosphatase score was elevated in only 46.2% of PV patients. The incidences of abnormal karyotypes were less than 10% in both PV and ET cases. The rates of transformation to myelofibrosis were 2.6% in both PV and ET cases, and acute leukemia was noted in 1.1% of PV patients and 2.9% of ET patients. Prognostic factors were thrombotic history for PV and thrombotic history and age (>or=60 years) for ET. The present study clearly demonstrated clinical differences between Japanese and Western patients for PV and ET. Concerning the treatment of PV and ET, the study revealed considerable variation among Japanese hematologists. These results suggest the necessity of developing treatment guidelines according to risk stratification that are suitable for Japanese PV and ET patients.

Leukocytosis is a risk factor for thrombosis in essential thrombocythemia: interaction with treatment, standard risk factors, and Jak2 mutation status

Leukocytes contribute to the pathogenesis of thrombosis in essential thrombocythemia (ET) through recently discovered mechanisms of activation and interaction with platelets and endothelial cells. To evaluate whether an increased leukocyte count was associated with thrombosis and whether this effect can be modulated by therapy, we analyzed the clinical course of 439 patients with ET followed at the Ospedali Riuniti di Bergamo. The strength of the association was measured at diagnosis or before thrombotic events by multivariable analyses carried out using data at baseline as well as time-varying covariates. The results showed that (1) an increased leukocyte count at diagnosis was associated with thrombosis during follow-up (“baseline analysis,” relative risk [RR] 2.3, 95% confidence interval [CI] 1.4-3.9, P = .001); (2) hydroxyurea (HU) lowered leukocytosis and reduced the strength of the association between leukocytosis and thrombosis (“time-dependent analysis,” RR 1.6, 95% CI 0.9-2.0, not significant [NS]); (3) the association of leukocytosis and thrombosis was more evident in untreated low-risk patients (RR 2.7, 95% CI 1.2-6.4, P = .01) compared with HU-treated high-risk patients (RR 1.6, 95% CI 0.8-3.2, NS); and (4) the presence of JAK2 V617F was not identified as a risk factor for thrombosis during follow-up despite a significant association between the mutation and leukocytosis. We suggest validation of these findings in prospective clinical studies.

JAK2V617F mutation in platelets from essential thrombocythemia patients: correlation with clinical features and analysis of STAT5 phosphorylation status

OBJECTIVE

JAK2V617F mutation rate in granulocytes from essential thrombocythemia (ET) patients ranges from 12% to 57%. Our aim was to evaluate the frequency of this mutation in the megakaryocyte/platelet lineage, and to analyze its clinical associations in ET. In addition, we determined whether this mutation leads to constitutive phosphorylation of STAT5 in platelets.

MATERIALS AND METHODS

Consecutive patients with ET were included and clinical features were retrospectively reviewed. Mutation detection was performed by allele specific RT-PCR (AS-RT-PCR) and Restriction fragment length polymorphism (RFLP) analysis of platelet RNA. Constitutive phosphorylation of STAT5 in platelets was studied by Western blot.

RESULTS

Fifty patients were included, 24 (48%) were JAK2V617F-positive by both AS-RT-PCR and RFLP. Patients with the mutation were older, had significantly higher hemoglobin levels, and lower platelet counts. Besides, higher frequency of thrombotic events was found in JAK2V617F-positive patients younger than 60, 53% vs. 4%, P = 0.0008. In addition, constitutive STAT5 phosphorylation was not detected in platelets from 12 patients.

CONCLUSIONS

The frequency of the JAK2V617F mutation in platelets was similar to that reported in granulocytes in the literature, suggesting this mutation does not occur as an isolated event in the megakaryocyte lineage. If confirmed in a larger study, the observed higher frequency of thrombosis in patients younger than 60 might be a useful predictive marker for thrombosis in this subset of patients. Even though this mutation has been predicted to constitutively activate the JAK2 kinase, spontaneous phosphorylation of STAT5 does not seem to be a frequent finding in platelets from ET patients.

Essential thrombocythemia: a review of diagnostic and pathologic features

CONTEXT

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

OBJECTIVE

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

DATA SOURCES

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

CONCLUSIONS

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

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Myeloproliferative disease in pregnancy and other management issues

The goal of this review is to assess the current treatment and outcomes of special clinical situations in patients with myeloproliferative disease (MPD) such as pregnancy, major thrombotic and bleeding complications and surgical interventions. However, only a limited literature to support optimal management strategies is available. Many of the proposed strategies are the results of common sense or derive from the extrapolation of data from other studies not specifically designed to solve these problems. Therefore, practical recommendations to guide clinical decisions in these settings still remain largely empirical.

Interferon-alfa treatment of essential thrombocythemia during pregnancy

We report on 2 successful pregnancies in a young woman who has essential thrombocythemia. The platelet count remained well controlled with interferon-alfa administration together with acetylsalicylic acid in each pregnancy. The present case and the published series suggest that close monitoring of the platelet count is crucial and that interferon may be the preferred therapeutic option in the management of pregnancy in patients with essential thrombocythemia.