scholarly journals The study of Jak2 V617F mutation in polycythemia vera with zebrafish model

Cell Research ◽  
2008 ◽  
Vol 18 (S1) ◽  
pp. S141-S141
Author(s):  
Alvin CH Ma ◽  
Alice MS Cheung ◽  
Alister C Ward ◽  
Wing-Yan Au ◽  
Yok-Lam Kwong ◽  
...  
Keyword(s):  
Polycythemia Vera ◽  
Jak2 V617f ◽  
Jak2 V617f Mutation ◽  
Zebrafish Model ◽  
V617f Mutation

Relation between JAK2 (V617F) mutation status, granulocyte activation, and constitutive mobilization of CD34+ cells into peripheral blood in myeloproliferative disorders

Blood ◽  
2006 ◽  
Vol 107 (9) ◽  
pp. 3676-3682 ◽  
Author(s):  
Francesco Passamonti ◽  
Elisa Rumi ◽  
Daniela Pietra ◽  
Matteo G. Della Porta ◽  
Emanuela Boveri ◽  
...  
Keyword(s):  
Polycythemia Vera ◽  
Gene Dosage ◽  
Jak2 V617f ◽  
Myeloproliferative Disorders ◽  
Jak2 V617f Mutation ◽  
Disease Category ◽  
Mutation Status ◽  
Cell Counts ◽  
Cd34 Cells ◽  
V617f Mutation

We studied the relationship between granulocyte JAK2 (V617F) mutation status, circulating CD34+ cells, and granulocyte activation in myeloproliferative disorders. Quantitative allele-specific polymerase chain reaction (PCR) showed significant differences between various disorders with respect to either the proportion of positive patients (53%-100%) or that of mutant alleles, which overall ranged from 1% to 100%. In polycythemia vera, JAK2 (V617F) was detected in 23 of 25 subjects at diagnosis and in 16 of 16 patients whose disease had evolved into myelofibrosis; median percentages of mutant alleles in these subgroups were significantly different (32% versus 95%, P < .001). Circulating CD34+ cell counts were variably elevated and associated with disease category and JAK2 (V617F) mutation status. Most patients had granulocyte activation patterns similar to those induced by administration of granulocyte colony-stimulating factor. A JAK2 (V617F) gene dosage effect on both CD34+ cell counts and granulocyte activation was clearly demonstrated in polycythemia vera, where abnormal patterns were mainly found in patients carrying more than 50% mutant alleles. These observations suggest that JAK2 (V617F) may constitutively activate granulocytes and by this means mobilize CD34+ cells. This exemplifies a novel paradigm in which a somatic gain-of-function mutation is initially responsible for clonal expansion of hematopoietic cells and later for their abnormal trafficking via an activated cell progeny.

scholarly journals JAK1 and Tyk2 Activation by the Homologous Polycythemia Vera JAK2 V617F Mutation

2005 ◽  
Vol 280 (51) ◽  
pp. 41893-41899 ◽  
Author(s):  
Judith Staerk ◽  
Anders Kallin ◽  
Jean-Baptiste Demoulin ◽  
William Vainchenker ◽  
Stefan N. Constantinescu
Keyword(s):  
Polycythemia Vera ◽  
Jak2 V617f ◽  
Jak2 V617f Mutation ◽  
V617f Mutation

Relationship between JAK2 V617F Mutation Status, Granulocyte CD177 mRNA Expression and CD177 Soluble Protein Level in Patients with Polycythemia Vera.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2578-2578
Author(s):  
Daniela Pietra ◽  
Alessandra Balduini ◽  
Carmela Marseglia ◽  
Matteo G. Della Porta ◽  
Luca Malcovati ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Polycythemia Vera ◽  
Protein Level ◽  
Mononuclear Cells ◽  
Jak2 V617f ◽  
Myeloproliferative Disorders ◽  
Jak2 V617f Mutation ◽  
Serum Samples ◽  
Close Relationship ◽  
V617f Mutation

Abstract A unique gain-of-function mutation of the Janus kinase 2 (JAK2) gene has been recently described in patients with polycythemia vera (PV), essential thrombocythemia and chronic idiopathic myelofibrosis [N Engl J Med. 2005 Apr 28;352(17):1779–90]. Although the currently available data clearly demonstrate that the JAK2 V617F mutation participates in the pathogenesis of myeloproliferative disorders, the mutation’s precise place in the hierarchical order of pathogenetic events remains to be established. We have recently reported that altered gene expression in myeloproliferative disorders correlates with activation of signaling by the V617F mutation of JAK2 (Blood. 2005 Aug 4; Epub ahead of print). Granulocyte CD177 (PRV1) mRNA overexpression has been initially reported as a potential marker of PV but later shown by us to rather be a marker of neutrophil activation [Br J Haematol. 2004 Sep;126(5):650–6]. In this study, we analyzed the relationship between JAK2 V617F mutation status, granulocyte CD177 mRNA expression and CD177 soluble protein level in 72 patients with PV. We also investigated the ontogeny of CD177 expression by hematopoietic cells with the aim of defining the stage of mRNA expression during myeloid, erythroid and megakaryocytic cell differentiation. Finally we studied the effect of soluble CD177 protein on hematopoietic cell proliferation and differentiation. Granulocyte CD177 mRNA expression and percentage of JAK2 V617F alleles were evaluated by quantitative Real Time PCR (qRT-PCR), while serum CD177 protein level was measured by a flow cytometry-based competitive antibody-binding assay. Liquid cultures were performed by culturing peripheral blood mononuclear cells obtained from healthy individuals and PV patients in the presence of high CD177-expressing, low CD177-expressing or CD177-depleted sera. After 12 days of culture, cells were collected, counted and evaluated for colony growth, and for flow cytometry analysis of myeloid, erythroid, megakaryocytic and CD34-positive cell subpopulations. qRT-PCR studies showed a close relationship between CD177 mRNA level and percentage of JAK2 V617F alleles (r=0.412, P&lt;0.001). CD177 mRNA expression was almost undetectable in cell populations other than granulocytes. Studies of CFU-GM growth and differentiation indicated that CD177 mRNA expression is a late event restricted to the neutrophil stage of differentiation. Analysis of serum samples showed variable values for mean fluorescence intensity (MFI), indicating variable levels of the soluble CD177 protein in the patients studied. A very close relationship was found between granulocyte CD177 mRNA expression and soluble CD177 protein level (r=0.56, P=0.02). Incubation of mononuclear cells with serum samples showing high levels of soluble CD177 protein resulted in increased numbers of CD34-positive cells (P&lt;0.02) and of erythroid progenitors (P&lt;0.03). This effect was not detectable when low CD177-expressing or CD177-depleted sera were employed. These observations clearly indicate that the JAK2 V617F mutation is associated with enhanced granulocyte CD177 mRNA expression, and that this latter results in high levels of soluble CD177 protein. These elevated levels might contribute to the increased red cell production that characterizes polycythemia vera.

In Vitro Expansion of Polycythemia Vera Progenitors Favors Expansion of Erythroid Precursors without JAK2 V617F Mutation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3506-3506 ◽  
Author(s):  
Josef T. Prchal ◽  
Ko-Tung Chang ◽  
Jaroslav Jelinek ◽  
Yongli Guan ◽  
Amos Gaikwad ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Polycythemia Vera ◽  
Peripheral Blood ◽  
Jak2 V617f ◽  
Jak2 V617f Mutation ◽  
Erythroid Progenitors ◽  
Erythroid Precursors ◽  
In Vitro Expansion ◽  
V617f Mutation

Abstract A single acquired point mutation of JAK2 1849G&gt;T (V617F), a tyrosine kinase with a key role in signal transduction from growth factor receptors, is found in 70%–97% of patients with polycythemia vera (PV). In the studies of tyrosine kinase inhibitors on JAK2 1849G&gt;T (see Gaikwad et all abstract at this meeting) we decided to study the possible therapeutic effect of these agents using native in vitro expanded cells from peripheral blood. To our surprise, the in vitro expansion of PV progenitors preferentially augmented cells without JAK2 1849G&gt;T mutation. We used a 3 step procedure to amplify erythroid precursors in different stages of differentiation from the peripheral blood of 5 PV patients previously found to be homozygous or heterozygous for the JAK2 1849G&gt;T mutation. In the first step (days 1–7), 106/ml MNCs were cultured in the presence of Flt-3 (50 ng/ml), Tpo (100 ng/ml), and SCF (100 ng/ml). In the second step (days 8–14), the cells obtained on day 7 were re-suspended at 106/ml in the same medium with SCF (50 ng/ml), IGF-1 (50 ng/ml), and 3 units/ml Epo. In the third step, the cells collected on day 14 were re-suspended at 106/ml and cultured for two more days in the presence of the same cytokine mixture as in the step 2 but without SCF. The cultures were incubated at 37oC in 5% CO2/95% air atmosphere and the medium renewed every three days to ensure good cell proliferation. The expanded cells were stained with phycoerythrin-conjugated anti-CD235A (glycophorin) and fluorescein isothiocyanate-conjugated anti-human-CD71 (transferrin receptor) monoclonal antibodies and analyzed by flow cytometry. The cells were divided by their differential expression of these antigens into 5 subgroups ranging from primitive erythroid progenitors (BFU-Es and CFU-Es) to polychromatophilic and orthochromatophilic erythroblasts; over 70% of harvested cells were early and late basophilic erythroblasts. The proportion of JAK2 1849G&gt;T mutation in clonal PV granulocytes (GNC) before in vitro expansion and in expanded erythroid precursors was quantitated by pyrosequencing (Jelinek, Blood in press) and is depicted in the Table. These data indicate that in vitro expansion of PV progenitors favors expansion of erythroid precursors without JAK2 V617F mutation. Since three PV samples were from females with clonal granulocytes, erythrocytes, and platelets, experiments were underway to determine if the in vitro expanded erythroid cells were clonal PV cells without JAK2 V617F mutation, or derived from polyclonal rare circulating normal hematopoietic progenitors. The Proportion of JAK2 T Allele Patients GNC T Allele (%) Expanded Cells T Allele (%) PV1 (Female) 81 10 PV2 (Male) 77 28 PV3 (Male) 44 42 PV4 (Female) 78 19 PV5 (Female) 78 28

Presence of JAK2 V617F Mutation in Peripheral Blood of Blood Donors with Upper-Limit Hematocrit and Platelet Values.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2533-2533
Author(s):  
Paola Bianchi ◽  
Elisa Fermo ◽  
Fulvio Mozzi ◽  
Maurizio Marconi ◽  
Alberto Zanella
Keyword(s):  
Polycythemia Vera ◽  
Blood Donors ◽  
Jak2 V617f ◽  
Jak2 V617f Mutation ◽  
Myeloid Metaplasia ◽  
Specific Pcr ◽  
Upper Limit ◽  
Allele Specific ◽  
V617f Mutation ◽  
Allele Specific Pcr

Abstract The somatic mutation V617F of JAK2 gene has been identified as a pathogenic factor in typical chronic myeloproliferative diseases (MPDs), in particular polycythemia vera, essential thrombocythemia, and myelofibrosis with myeloid metaplasia. Recently, two studies showed the presence of this mutation also in 37/3935 subjects with non haematological diseases (Xu et al, 2006) and 5/52 healthy donors (Sidon et al, 2006), suggesting that V617F mutation may occur in the absence of MPD phenotype and that probably is not sufficient per se to induce MPDs. The aim of this study was to search for the presence of JAK2 V617F mutation in healthy blood donors with confirmed upper-limit Hct and/or Plts values. Actually, previous studies indicated that some subjects with upper-limit Hct levels have early stages of polycythemia vera (Zanella et al, 1987). We studied 177 consecutive repeat blood donors (92 M, 85 F; median age 45 years, range 19–66) displaying Hct and/or Plts values higher than the 75° percentile of the normal reference distribution (Hct &gt; 0.47 for M and &gt; 0.42 for F; Plts &gt; 300×109/L), confirmed on at least two different occasions in the last 12 months. All subjects had been accepted for blood donation on the basis of negative clinical history and normal results on both physical examination and routine laboratory testing. 83 of them (55 M and 28 F) had upper-limit Hct levels (median 0.48, range 0.47-0.51 for M; 0.43, range 0.42-0.47 for F); 85 had Plts &gt; 300×109/L (median 338×109/L, range 300–454), and 9 donors had both upper-limit Hct and Plts. DNA was extracted from whole blood; all samples were analyzed by allele-specific polymerase chain reaction (PCR) according to Baxter et al (2005), and by fluorescent allele specific PCR (McClure et al, 2006) on ABI PRISM 310 Genetic Analyzer. Ten subjects were found to be positive for V617F mutation by fluorescent PCR, showing a positive signal when compared to a positive control corresponding to 2% of V617F mutated allele. Six of them showed a positive band also on agarose gel when analyzed with allele specific PCR. The presence of mutation was confirmed by enzymatic digestion with BsaXI. Hematological data of mutated subject are reported in the table. No statistically significant differences of hematological parameters were present between V617F positive and negative subjects. In conclusion, the presence of a V617F positive clone (albeit in a small amount), was found in 4% (3 F and 1 M) donors with upper-limit Hct and in 6% (2 F, 4 M) donors with Plts &gt; 300×109/L. The follow up of these subjects will ascertain whether V617F mutation is a prelude to a myeloproliferative disease. Sex Age (years) Hb (g/dl) Hct Plts (×109/L) WBC (x109/L) Upper-limit Hct 1 F 66 15.1 0.45 202 4.85 2 F 51 14.4 0.43 235 6.40 3 F 64 15.7 0.45 198 7.75 4 M 58 15.9 0.48 220 7.30 Plts &gt; 300×109/L 5 F 53 13.7 0.40 360 6.97 6 F 63 13.5 0.40 301 9.2 7 M 47 15.2 0.45 334 8.64 8 M 47 13.8 0.41 316 6.35 9 M 19 15.2 0.44 321 8 10 M 37 16.1 0.45 379 7.9

JAK2 Mutation Status in Granulocytes, Platelets and Erythrocytes Differs Between Polycythemia Vera and Essential Thrombocythemia

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 5228-5228
Author(s):  
Kohtaro Toyama ◽  
Norifumi Tsukamoto ◽  
Akio Saito ◽  
Hirotaka Nakahashi ◽  
Yoko Hashimoto ◽  
...  
Keyword(s):  
T Cells ◽  
Polycythemia Vera ◽  
Essential Thrombocythemia ◽  
Mononuclear Cells ◽  
Rna Extraction ◽  
Jak2 V617f ◽  
Janus Kinase ◽  
Jak2 V617f Mutation ◽  
Mutation Status ◽  
V617f Mutation

Abstract Background The gain-of-function point mutation in Janus kinase 2 exon 14 gene (JAK2-V617F) influences the diagnosis of bcr/abl-negative chronic myeloproliferative disorders (CMPDs). We previously reported that analyzing platelets is advantageous in detecting the JAK2-V617F mutation, particularly in essential thrombocythemia (ET), when compared to granulocytes. However, there have been few reports analyzing the JAK2-V617F mutation in erythroid lineage cells, and comparing the mutation status in all three lineages. Method Study protocols were approved by the Institutional Review Board of Gunma University Hospital, and written informed consent was obtained from all the patients. Heparinized peripheral blood was obtained from 113 patients with CMPDs (82 with ET, 25 with polycythemia vera (PV), and 6 with primary myelofibrosis (PMF). After centrifugation, platelets were collected from the upper plasma layer. Remaining blood was mixed with Hank’s Balanced Salt Solution and was subjected to Ficoll-Hypaque density gradient centrifugation. Granulocytes were obtained from the pellet. Mononuclear cells were resuspended in RPMI 1640 medium; 5 × 105 cells were plated in duplicate in 1 ml of methylcellulose medium and cultured in a humidified atmosphere of 5 % of carbon dioxide at 37°C for 14 days in the presence of erythropoietin to obtain erythroid colonies (BFU-E). T-cells were obtained from the remaining mononuclear cells using anti-CD3 immunoconjugated magnetic beads. After extraction of DNA from granulocytes, T-cells and BFU-E, and RNA extraction from granulocytes and platelets, PCR amplification and sequencing of exon 14 of the Jak2 gene was performed to confirm the presence of JAK2-V617F mutations. To confirm the mutation status of granulocytes, T-cells and BFU-E, allele-specific PCR (AS-PCR) was performed. Results For ET, 57 out of 82 patients (69.5%) had the JAK2-V617F mutation. In the 57 patients with the JAK2-V617F mutation, 38 (67%) had the mutation in all three lineages, 5 had the mutation in granulocytes and platelets, 2 had the mutation in platelets and BFU-E, 10 patients had the mutation only in platelets and 2 patients had the mutation only in BFU-E. In contrast, for PV, 22/25 patients (88%) had the JAK2-V617F mutation. Of note, in 22 patients having JAK2-V617F mutation, 20 (91%) were JAK2-V617F mutation-positive in all three lineages; the remaining two patients had the mutation in either platelets or BFU-E. The frequency of JAK2-V617F in all three lineages was significantly higher in PV than in ET (p &lt; 0.05). For PMF, 5 of 6 patients had the mutation in granulocytes, and 3 of these had it in all three lineages. Conclusion Among JAK2-V617F mutation-positive CMPDs, most PV patients had the JAK2-V617F mutation in all three lineages, thus suggesting that the JAK2-V617F mutation occurs in progenitor cell(s) common to granulocytes, platelets and erythrocytes. In contrast, only 67% of ET patients had the JAK2-V617F mutation in three lineages; in the remaining cases, not all of the three lineages have the mutation. This difference in lineages showing the JAK2-V617F mutation between the ET and PV may be related to the pathophysiological differences in ET and PV. Furthermore, the heterogeneous mutation status in ET may be related to its heterogeneous clinical manifestation.

LY2784544, a Novel JAK2 Inhibitor, Decreases In Vitro Growth of Hematopoietic Human Progenitors From JAK2 V617F Positive Polycythemia Vera Patients

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 5054-5054 ◽  
Author(s):  
Lourdes Florensa ◽  
Beatriz Bellosillo ◽  
Leonor Arenillas ◽  
Liandong Ma ◽  
Richard Walgren ◽  
...  
Keyword(s):  
Polycythemia Vera ◽  
Peripheral Blood ◽  
Mononuclear Cells ◽  
Jak2 V617f ◽  
Jak2 V617f Mutation ◽  
Dependent Manner ◽  
In Vitro Growth ◽  
Vitro Assay ◽  
V617f Mutation

Abstract Abstract 5054 Introduction: The discovery of JAK2 V617F mutation in patients with myeloproliferative disorders (MPD) has opened new perspectives for the development of targeted therapies. We have studied the efficacy of a novel molecule LY2784544 with JAK2 inhibitory activity in the in vitro growth of myeloid progenitors from JAK2 V617F-positive polycythemia vera (PV) patients. Objectives: To investigate the efficacy of LY2784544 in the inhibition of endogenous(e)BFU-E and CFU-GM growth in PV patients. Methods: In vitro cultures in semisolid media were performed from peripheral blood mononuclear cells (PBMC) of 6 PV patients who had never received cytoreductive treatment (4 patients with homozygous JAK2 V617F and 2 patients with heterozygous JAK2 V617F). PBMC were suspended in methylcellulose (Methocult. StemCell, Vancouver, Canada) without the addition of EPO and containing 0–30.0 μM LY2784544 drug. Concurrent plates containing EPO were plated as control cultures. The medium was distributed in multidishes and they were incubated at 37° with 5% CO2 and 95% humidity. Hemoglobinized colonies and granulomonocytic colonies were counted on day 14 by standard criteria (BFU-E defined by an aggregate of >50 hemoglobinized cells or three or more erythroid subcolonies and CFU-GM was defined by an aggregate of >50 cells). Each in vitro assay was performed in duplicate. DNA was obtained from peripheral blood granulocytes from each patient to quantify the JAK2 V617F allele burden at the time of culture assay. Results: LY2784544, at concentrations ranging from 0.03–30.0 μM, inhibited growth of unselected peripheral blood eBFU-E and CFU-GM from PV patients carrying the JAK2 V617F mutation in a dose-dependent manner, although without achieving complete inhibition of all colonies (fig.1). Conclusions: In vitro studies show that LY2784544 decreases the eBFU-E and CFU-GM growth in therapy-naive JAK2 V617F positive PV patients. Our data suggest that LY2784544 may be a candidate for the treatment of MPD carrying the JAK2 V617F mutation. Disclosures: Ma: Eli Lilly and Company: Employment. Walgren:Eli Lilly and Company: Employment.

Analysis of JAK2 V617F Mutation and Its Clinical Significance in Patients with Thrombocythemia and Other Myeloproliferative Neoplasms in Chinese

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4687-4687
Author(s):  
Yue Xu ◽  
Changxin Yin ◽  
Han He ◽  
Lingling Shu ◽  
Fuqun Wu ◽  
...  
Keyword(s):  
Polycythemia Vera ◽  
Essential Thrombocythemia ◽  
Conflicts Of Interest ◽  
Myeloproliferative Neoplasms ◽  
Jak2 V617f ◽  
Jak2 V617f Mutation ◽  
Jak2 Mutation ◽  
Western Countries ◽  
Arms Pcr ◽  
V617f Mutation

Abstract Abstract 4687 JAK2 mutation is commonly found in Philadelphia-negative myeloproliferative neoplasms (MPNs). In Western countries, this mutation is found in approximately 96 percent of people with polycythemia vera, half of individuals with essential thrombocythemia or primary myelofibrosis. We used the method of amplification refractory mutation PCR (ARMS-PCR) to investigate MPN patients in China. We focused our study on patients with essential thrombocythemia (ET). ARMS-PCR was used to detect JAK2 V617F mutation in the bone barrow (BM) or peripheral blood of 37 MPN patients, which consisting of 7 ET, 5 polycythemia vera (PV), 5 chronic myeloid leukemia (CML), 5 chronic idiopathic myelofibrosis (CIMF), as well as 15 suspected MPNs. 17 cases of JAK2 V617F mutation (45.9%) were found in 37 patients, including 4 ET (57.1%), 4 PV (80.0%), 3 CIMF (60.0%), 6 suspected MPNs (40.0%). We did not find JAK2 V617F in the patients with CML. Our results indicated that the frequency of JAK2 V617F mutation in bcr/abl-negative MPNs in Chinese is similar to that in MPN patients in Western countries. At the same time, ARMS-PCR can distinguish the mutation is heterozygous or homozygous. Most patients were heterozygous for JAK2 but only a few were homozygous. In conclusion, our study showed that JAK2 V617F mutation frequency in Chinese MPN patients is similar to that in patients with this disorder in the West. It is the major molecular genetic abnormality in bcr-abl negative MPN and it can be used for diagnosis of MPN in China. Disclosures: No relevant conflicts of interest to declare.

The Red Cell Mass (RCM) Value In Polycythaemia Vera Disease In The JAK2 V617F Era

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 5249-5249 ◽  
Author(s):  
Hassan A. Al-Jafar ◽  
Leena M Aytoglu ◽  
Issa Loutfi ◽  
Iman Al-Shemmari ◽  
Salem H Alshemmari
Keyword(s):  
Polycythemia Vera ◽  
Cell Mass ◽  
Jak2 V617f ◽  
Myeloproliferative Disorders ◽  
Jak2 V617f Mutation ◽  
Polycythaemia Vera ◽  
Red Cell ◽  
Red Cell Mass ◽  
V617f Mutation ◽  
Idiopathic Erythrocytosis

Abstract Introduction In Polycythaemia Vera (PV), the RBC lineage is involved with increased haemoglobin, RBC count and haematocrit. WHO diagnostic criteria for PV are JAK2 V617F mutation and elevated red cell mass (RCM) > 25% of mean normal value. In addition, tests of marrow hypercellularity, blood erythropoietin and colony formation, are minor criteria. However, the diagnostic role of RCM test is still controversial and requires clarification. In this work, PV patients who had both an RCM study and JAK2 V617F mutation test, and routine laboratory tests, are evaluated to check if RCM was essential in the diagnostic work up for PV. Methods Over 2 years, 75 patients with abnormal haematocrit (men ≥ 0.50, women ≥ 0.45) had RCM and JAK2 V617F mutation tests (except JAK2 exon 12 mutation). All subjects consented to the study approved by the ethics committee. RCM was done by Cr-51 RBC radiolabeling method (no prior venesection at least 1 month). Statistical analysis involved descriptive statistics and chi-square test. Results There were 71 males and 4 females, mean age 46 y (range 17-75 y). Increased RCM was found in 41/75 (55%). Positive JAK2 V617F was found in 13/75 patients (17%), who also had RCM above the mean normal predicted value, however, when the WHO RCM criteria were applied, only 7/13 (54%) could be considered as having “truly” increased RCM. In the patient group with negative JAK2 V617F test, 12/28 (43%) had RCM results as per WHO criteria. There was no statistical association between presence of JAK2 V617F and the RCM values. Conclusion In patients with negative JAK2 V617F but with high clinical suspicion for PV and all other causes of secondary and idiopathic erythrocytosis excluded, an increase in RCM would support the diagnosis of PV (about 10 % PV cases). In patients with JAK2 positive mutation and high haematocrit but RCM below the WHO cut-off level, an increased RCM would still count to confirm the diagnosis as the current standard level seems too stringent. References James C, Ugo V, Le Couedic JP, Staerk J, Delhommeau F, Lacout C et al. A unique clonal JAK2 mutation leading to constitutive signaling causes polycythaemia vera. Nature 2005; 434(7037): 1144-8. Kralovics R, Passamonti F, Buser AS, Soon-Siong T, Tiedt R, Passweg JR, et al. A Gain-of-Function Mutation of JAK2 in Myeloproliferative Disorders. Merck Manual of Diagnosis and Therapy. 16th Edition, 1992 McMullin MF, Bareford D, Campbell P, Green AR, Claire Harrison C, Hunt B, Oscier D, et al. Guidelines for the diagnosis, investigation and management of polycythaemia/erythrocytosis. British Journal of Haematology 2005; 130(2): 174-95. Scott LM, Tong W, Levine RL, et al. JAK2 exon 12 mutations in polycythemia vera and idiopathic erythrocytosis. N Engl J Med. 2007;356:459-468. Pardanani A, Lasho TL, Finke C, et al. Prevalence and clinicopathologic correlates of JAK2 exon 12 mutations in JAK2V617F-negative polycythemia vera. Leukemia. 2007;21:1960-1963. Pancrazzi A, Guglielmelli P, Ponziani V, et al. A sensitive detection method for MPLW515L or MPLW515K mutation in chronic myeloproliferative disorders with locked nucleic acid-modified probes and real-time polymerase chain reaction. J Mol Diagn. 2008;10:435-441. Disclosures: No relevant conflicts of interest to declare.

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