Prevalence of overt myeloproliferative neoplasms and JAK2 V617F mutation in Korean patients with splanchnic vein thrombosis

Introduction: Myeloproliferative neoplasm (MPN) is known to be a major risk factor of splanchnic vein thrombosis (SVT). Recent studies revealed that a significant proportion of patients with SVT harbor a gain‐of‐function mutation in the JAK2 gene (V617F) with or without MPN. In this study, the authors investigated the prevalence of MPN and JAK2 V617F mutation in Korean patients with SVT. Methods: The study subjects were 26 patients diagnosed as having SVT based on Doppler ultrasound and/or computed tomography from January 2008 to January 2010 (16 men and 10 women; mean age 44 years, range 15–75 years). The clinical and laboratory data were reviewed. The JAK2 V617F mutation was detected by allele‐specific polymerase chain reaction and direct sequencing analyses using DNA from peripheral blood leukocytes. Results: Among 26 study patients, 12 had portal vein thrombosis, five had hepatic vein thrombosis, three had mesenteric, and two had splenic vein thrombosis. Four patients had thrombosis involving more than one splanchnic vein. Two patients (7.7%; 2/26) had overt MPN (essential thrombocythemia). JAK2 V617F was detected in three patients (11.5%) including the two patients with overt MPN. Thus, the prevalence of the JAK2 V617F mutation in patients with SVT but without overt MPN was 4.2% (1/24). Conclusion: The prevalence of overt MPN and that of JAK2 V617F were lower in Korean patients with SVT than in previous reports. Data from a larger number of patients with long‐term follow‐up are needed to reveal the clinical relevancy of JAK2 V617F in Korean patients with SVT.     

The JAK2 46/1 haplotype in Budd-Chiari syndrome and portal vein thrombosis

The germline JAK2 46/1 haplotype has been associated with the development of JAK2(V617F)-positive as well as JAK2(V617F)-negative myeloproliferative neoplasms (MPNs). In this study we examined the role of the 46/1 haplotype in the etiology and clinical presentation of patients with splanchnic vein thrombosis (SVT), in which MPNs are the most prominent underlying etiological factor. The single-nucleotide polymorphism rs12343867, which tags 46/1, was genotyped in 199 SVT patients. The 46/1 haplotype was overrepresented in JAK2(V617F)-positive SVT patients compared with controls (P < .01). Prevalence of the 46/1 haplotype in JAK2(V617F)-negative SVT patients did not differ from prevalence in the controls. However, JAK2(V617F)-negative SVT patients with a proven MPN also exhibited an increased frequency of the 46/1 haplotype (P = .06). Interestingly, 46/1 was associated with increased erythropoiesis in JAK2(V617F)-negative SVT patients. We conclude that the 46/1 haplotype is associated with the development of JAK2(V617F)-positive SVT. In addition, our findings in JAK2(V617F)-negative SVT patients indicate an important role for the 46/1 haplotype in the etiology and diagnosis of SVT-related MPNs, independent of JAK2(V617F), that requires further exploration.     

Prevalence of the JAK2V617F mutation in Chinese patients with Budd-Chiari syndrome and portal vein thrombosis: a prospective study

Background and Aim: Whether routine screening for the JAK2V617F mutation should be performed in Chinese patients with Budd‐Chiari syndrome (BCS) and portal vein thrombosis (PVT) is unclear. Therefore, we aimed to evaluate the prevalence of the JAK2V617F mutation in such patients and to explore the risk factors associated with the mutation. Methods: All consecutive patients with BCS and PVT diagnosed between September 2009 and May 2011 were prospectively enrolled in the observational study and underwent the JAK2V617F mutation detection. Results: Prevalence of the JAK2V617F mutation was 4.3% (4/92) in patients with primary BCS, 26.6% (17/64) in non‐malignant and non‐cirrhotic patients with PVT, and 1.4% (1/71) in cirrhotic patients with PVT. All BCS patients with the JAK2V617F mutation had both platelet count (PLT) of above 100 × 10⁹/L (range, 107–188 × 10⁹/L) and splenomegaly. In non‐malignant and non‐cirrhotic patients with PVT, higher PLT and older ages were the independent predictors of the JAK2V617F mutation. Further, the difference in PLT between the patients with and without the mutation displayed greater significance in the subgroup of patients with splenomegaly (P < 0.0001), but the statistical significance disappeared in the subgroup of patients with splenectomy (P = 0.1312). Conclusions: The low prevalence of the JAK2V617F mutation in patients with BCS suggests that myeloproliferative neoplasm should be an uncommon etiological factor of BCS in China. Routine screening for the JAK2V617F mutation might be recommended in non‐malignant and non‐cirrhotic patients with PVT, but not in cirrhotic patients with PVT. The coexistence of higher PLT and splenomegaly might be closely associated with the JAK2V617F mutation.     

JAK2 (V617F) Positive Latent Myeloproliferative Neoplasm Presenting with Splanchnic Vein Thrombosis

Myeloproliferative neoplasms (MPNs) are chronic clonal hematopoietic stem cell disorders characterized by proliferation of one or more of the granulocytic, red cell or platelet lineages in the bone marrow, with fairly normal maturation, resulting in increase in the leukocyte, erythrocytes and platelets in the blood. They also represent a common cause of splanchnic vein thrombosis (SVT). Herein, we describe a case of SVT as a presenting symptom of latent MPN. The patient has had normal complete blood counts since presentation. 3 ½ years later, she was found to have JAK2 (V617F) mutation and bone marrow biopsy was consistent with MPN. Five years later, her platelet count started to rise. In patients with a first episode of SVT, thrombophilia workup including JAK2 (V617F) mutation is warranted. Anticoagulation with heparin and warfarin is the treatment of choice for SVT.     

Relevance of the JAK2V617F mutation in patients with deep vein thrombosis of the leg

Venous thromboembolism (VTE) can be the first presenting symptom in myeloproliferative neoplasms (MPN). Studies have demonstrated a high prevalence of the JAK2V617F mutation in patients with splanchnic vein thrombosis. Fewer studies have been done in patients with thrombosis outside the splanchnic area, showing a lower prevalence although the clinical relevance of the mutation in these patients, e.g., progression to overt MPN, remains unknown. The objective of this study was to determine the effect size of JAK2V617F in prospectively collected DNA samples of patients objectively diagnosed with deep vein thrombosis (DVT) of the leg and controls without DVT, with follow-up on JAK2V617F-positive patients to assess clinical relevance. Presence of JAK2V617F was determined in DNA samples from 187 patients with DVT and 201 controls, using quantitative RT-PCR. Hematological parameters were also analyzed. All initially JAK2V617F-positive patients were reassessed. Of 187 patients with DVT, 178 were analyzed for JAK2V617F, and in four (2.3%; 95% CI 0.1–4.4), JAK2V617F was present. Of 201 controls, 198 were analyzed; one was JAK2V617F positive (0.5%; 95% CI −0.5–1.5, OR 4.5; 95% CI 0.5–40.9). None had MPN features, nor upon reassessment after a median follow-up of 68.5 months. Four JAK2V617F-positive patients with DVT and one control without DVT did not develop overt MPN after a median follow-up of nearly 6 years. Thus, in patients with non-splanchnic venous thrombosis, JAK2V617F appears not to be clinically relevant.     

The impact of JAK2 and MPL mutations on diagnosis and prognosis of splanchnic vein thrombosis: a report on 241 cases

Myeloproliferative diseases (MPDs) represent the commonest cause of splanchnic vein thrombosis (SVT), including Budd-Chiari syndrome (BCS) and portal vein thrombosis (PVT), but their diagnosis is hampered by changes secondary to portal hypertension, while their influence in the outcome of SVT remains unclear. We assessed the diagnostic and prognostic value of JAK2 and MPL515 mutations in 241 SVT patients (104 BCS, 137 PVT). JAK2V617F was found in 45% of BCS and 34% of PVT, while JAK2 exon 12 and MPL515 mutations were not detected. JAK2V617F was found in 96.5% of patients with bone marrow (BM) changes specific for MPD and endogenous erythoid colonies, but also in 58% of those with only one feature and in 7% of those with neither feature. Stratifying MPD diagnosis first on JAK2V617F detection would have avoided BM investigations in 40% of the patients. In BCS, presence of MPD carried significantly poorer baseline prognostic features, required hepatic decompression procedures earlier, but had no impact on 5-year survival. Our results suggest that JAK2V617F testing should replace BM investigations as initial test for MPD in patients with SVT. Underlying MPD is associated with severe forms of BCS, but current therapy appears to offset deleterious effects of MPD on the medium-term outcome.      

JAK2 V617F and beyond: role of genetics and aberrant signaling in the pathogenesis of myeloproliferative neoplasms

Dysregulated signaling is a hallmark of chronic myeloproliferative neoplasms (MPNs), as evidenced by the identification of the activating JAK2 V617F somatic mutation in almost all patients with polycythemia vera (PV) and 50-60% of essential thrombocythemia and primary myelofibrosis patients. These disorders are clinically distinct, raising the question of how a single mutation can result in such phenotypic diversity. Mouse models have demonstrated that the level of JAK2 V617F expression can modulate the phenotype, and clinical studies of JAK2 V617F allele burden have reported similar findings. It has also been hypothesized that one or more pre-JAK2 V617F events may modify the MPN phenotype. However, the molecular basis of JAK2 V617F-negative essential thrombocythemia and primary myelofibrosis remains largely unexplained. Mutations in the TET2 gene have been identified in both JAK2 V617F-positive and -negative MPNs and other myeloid neoplasms, but their functional and clinical significance have yet to be clarified. In addition, recent reports have identified a specific germline haplotype that increases the predisposition to MPNs. The role of inhibitory pathways (e.g., SOCS and LNK) in regulating JAK-STAT signaling in MPNs is being increasingly recognized. The implications of these findings and their clinical relevance are the focus of this article.     

Prevalence of the activating JAK2 tyrosine kinase mutation V617F in the Budd-Chiari syndrome

BACKGROUND & AIMS: Budd-Chiari Syndrome (BCS) results from obstruction to hepatic venous outflow, with myeloproliferative disorder (MPD) accounting for up to 40% of cases. A number of BCS cases labelled as "idiopathic" do not fulfill the diagnostic criteria for MPD but have features suggestive of a latent form based on hyperplastic bone marrow and erythroid progenitor cell culture; these cases may subsequently develop overt MPD. A clonal mutation in JAK2 tyrosine kinase (JAK2V617F) occurs in a high proportion of patients with MPD and is of use in the characterization of latent MPD in BCS. METHODS: We performed allele-specific polymerase chain reaction to screen for JAK2V617F in subjects with BCS (n = 41) and polycythemia vera (PV) (n = 20) and in hematologically normal controls (n = 27). RESULTS: AK2V617F was detected in 24 of 41 (58.5%) subjects with BCS, 19 of 20 PV controls, and 0 of 27 hematologically normal controls. Mean hemoglobin concentration and hematocrit were significantly higher in patients with JAK2V617F. Bone marrow was hyperplastic in 16 of 41 subjects (12/16 JAK2V617F positive). Nine of 33 (27.3%) showed endogenous erythroid colony formation (7/9 JAK2V617F positive). Eleven of 41 subjects developed overt MPD (8/11 essential thrombocythemia, 3/11 PV) after the diagnosis of BCS (median, 49 months; range, 8-87 months), and in 90.9% of these JAK2V617F was detected. CONCLUSIONS: JAK2V617F occurs in a high proportion of patients with BCS. Latent MPD was missed in a substantial number of our subjects by using standard techniques. Such cases should be screened for JAK2V617F and carefully observed for the subsequent development of overt MPD.     

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.     

JAK2 (V617F) mutation is not associated with thrombosis in Behcet syndrome

The Janus kinase 2(V617F) (JAK2 (V617F)) mutation is an acquired genetic defect that is considered to enhance thrombosis in Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs). Thrombosis is also a well-defined component of Behcet syndrome (BS). The aim of this study was to determine the frequency of JAK2 ( V617F ) mutation in BS-associated thrombosis. A total of 152 patients with BS (62 with thrombosis and 90 without thrombosis) were enrolled. An additional 186 patients with MPNs and 107 healthy blood donors were included to serve as diseased and healthy controls, respectively. None of the patients with BS and healthy controls carried the JAK2 (V617F) mutation, whereas 67% of patients with MPNs were positive for JAK2 ( V617F ). The frequency of thrombosis in patients with MPNs was not statistically different between carriers and non-carriers of JAK2 ( V617F ) mutation. Our data suggest that JAK2 (V617F) is not directly related to thrombosis in MPNs and in other thrombotic entities, such as BS.     

Tyrosine 201 is required for constitutive activation of JAK2V617F and efficient induction of myeloproliferative disease in mice

The JAK2V617F mutation has been detected in most cases of Ph-negative myeloproliferative neoplasms (MPNs). The JAK2V617F protein is a constitutively activated tyrosine kinase that leads to transformation of hematopoietic progenitors. Previous studies have shown that several tyrosine residues within JAK2 are phosphorylated on growth factor or cytokine stimulation. However, the role of these tyrosine residues in signaling and transformation mediated by JAK2V617F remains unclear. In this study, we sought to determine the role of tyrosine 201, which is a potential binding site for Src homology 2 domain-containing proteins, in JAK2V617F-induced hematopoietic transformation by introducing a tyrosine-to-phenylalanine point mutation (Y201F) at this site. We observed that the Y201F mutation significantly inhibited cytokine-independent cell growth and induced apoptosis in Ba/F3-EpoR cells expressing JAK2V617F. The Y201F mutation also resulted in significant inhibition of JAK2V617F-mediated transformation of hematopoietic cells. Biochemical analyzes revealed that the Y201F mutation almost completely inhibited constitutive phosphorylation/activation of JAK2V617F. We also show that the Y201 site of JAK2V617F promotes interaction with Stat5 and Shp2, and constitutive activation of downstream signaling pathways. Furthermore, using a BM transduction/transplantation approach, we found that tyrosine 201 plays an important role in the induction of MPNs mediated by JAK2V617F.     

Relationship between JAK2V617F mutation,allele burden and coagulation function in Ph-negative myeloproliferative neoplasms

Objectives: Our aim was to explore the relationship between JAK2V617F mutation allele burden and hematological parameters especially in coagulation function in Chinese population.

Methods: This study included 133 Ph-negative myeloproliferative neoplasms (MPNs) patients between 2013 and 2016. All the clinical and experimental data of patients were collected at the time of the diagnosis without any prior treatment, including blood parameters, coagulation function, splenomegaly, vascular events and chromosome karyotype. PCR and qPCR were used to detect JAK2V617F mutation and JAK2V617F mutation allele burden.

Results: In polycythemia vera patients, a positive correlation between the allele burden of JAK2V617F mutation and PLT counts was found; in essential thrombocythemia (ET) patients, WBC counts, RBC counts, HB, and HCT were higher in mutated patients than in wild-type patients. Furthermore, PT-INR was higher in ET and PMF mutated patients. In addition, a positive correlation between the allele burden of JAK2V617F mutation and activated partial thromboplastin time (APTT) was observed in JAK2V617F mutated ET patients.

Conclusions: Higher hematologic parameters including counts of WBC, RBC, and PLT are closely associated with JAK2V617F mutation and its burden in Ph-negative MPNs; importantly, PT-INR, APTT are also related to JAK2V617F mutation and allele burden. Thus, our data indicate that JAK2V617F mutation allele burden might not only represent the burden of MPN but also alter the coagulation function.     

Evaluation of the prevalence and prospective clinical impact of the JAK2 V617F mutation in coronary patients

The JAK2 V617F mutation is not only found in the majority of patients with myeloproliferative neoplasms (MPN), including essential thrombocythemia (ET), but also has been reported in individuals without overt MPN. A close relation of the JAK2 V617F mutation to atherothrombotic events has been described, at least in patients with MPN. The prevalence of the JAK2 V617F mutation and its clinical impact in coronary patients is unknown. To address this issue, DNA samples from 1,589 subjects undergoing coronary angiography with up to 11 years of follow up were genotyped using allele‐specific real‐time PCR assays. Prevalence of the JAK2 V617F mutation was 1.32% (n = 21) in coronary patients. Two JAK2 V617F positive patients showed baseline platelet counts indicative for ET and a third patient developed ET during follow up, finally resulting in a percentage of 0.188% of ET cases. This corresponds to an up to fivefold accumulation of ET cases in coronary patients compared with the general population. Our study showed no impact of the JAK2 V617F mutation on future atherothrombotic events or overall survival (HR = 1.04 [0.33–3.27]; P = 0.949 and HR = 0.35 [0.05–2.46]; P = 0.288, respectively). Therefore, our data suggest that JAK2 V617F positive coronary patients are not at increased risk for future atherothrombotic complications. Routine mutation screening in coronary patients is, therefore, not warranted. However, number of ET cases appears to be accumulated in coronary patients. For this reason, we recommend JAK2 V617F testing only in coronary patients showing abnormal blood cell counts for further clarification. Am. J. Hematol. 89:295–301, 2014. © 2013 Wiley Periodicals, Inc.     

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.     

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.     

Critical requirement for Stat5 in a mouse model of polycythemia vera

The JAK2V617F mutation has been identified in most cases of Ph-negative myeloproliferative neoplasms (MPNs) including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Expression of JAK2V617F results in constitutive activation of multiple signaling molecules/pathways. However, the key signaling downstream of JAK2V617F required for transformation and induction of MPNs remains elusive. Using a mouse genetic strategy, we show here that Stat5 is absolutely required for the pathogenesis of PV induced by Jak2V617F. Whereas expression of Jak2V617F in mice resulted in all the features of human PV, including an increase in red blood cells, hemoglobin, hematocrit, white blood cells, platelets, and splenomegaly, deletion of Stat5 in the Jak2V617F knockin mice normalized all the blood parameters and the spleen size. Furthermore, deletion of Stat5 completely abrogated erythropoietin (Epo)-independent erythroid colony formation evoked by Jak2V617F, a hallmark feature of PV. Re-expression of Stat5 in Stat5-deficient Jak2V617F knockin mice completely rescued the defects in transformation of hematopoietic progenitors and the PV phenotype. Together, these results indicate a critical function for Stat5 in the pathogenesis of PV. These findings also provide strong support for the development of Stat5 inhibitors as targeted therapies for the treatment of PV and other JAK2V617F-positive MPNs.     

No Evidence for JAK2 Mutation in Monoclonal B Cells in 2 Patients with Polycythaemia Vera and Concurrent Monoclonal B Cell Disorder

Occurrence of Philadelphia chromosome-negative myeloproliferative neoplasms (Ph(-) MPN) and lymphoproliferative disorders, like B cell chronic lymphocytic leukaemia (B-CLL), in the same patient is rare. JAK2(V617F) mutation was recently introduced as a powerful diagnostic tool for Ph(-) MPN. JAK2(V617F) mutation is not present in B-CLL. In 4 previously reported patients with JAK2(V617F)-positive Ph(-) MPN and B-CLL there was no definitive proof of JAK2(V617F) mutation in B-CLL cells, although this was suggested in 1 patient. We present 2 patients with JAK2(V617F)-positive polycythaemia vera who subsequently developed a monoclonal B cell disorder. The granulocytes were separated from the mononuclear cells by centrifugation on density gradient. Using an ARIA-SORP sorter, the CD20+/CD5+ B cells were separated from the CD20+/CD5- B cells, T cells, NK cells and monocytes. On each of the fractions JAK2(V617F) mutation was analysed by allele-specific competitive blocker-PCR. In both patients JAK2(V617F) mutation was present in granulocytes confirming the clinical diagnosis of polycythaemia vera. We did not detect the JAK2(V617F) mutation in the CD20+/CD5+ B cells but detected it in CD20+/CD5- B cells, T and NK cells, indicating a lymphoid subdifferentiation of the JAK2(V617F) MPN clonality. JAK2(V617F) MPN and monoclonal B cell disorder can coexist but there is no evidence that the proliferative behaviour of these B cells is mediated through the JAK2(V617F) mutation.     

Renovascular hypertension associated with JAK2 V617F positive myeloproliferative neoplasms treated with angioplasty: 2 cases and literature review

Myeloproliferative neoplasms (MPNs) with Janus kinase 2 (JAK2) mutation are associated with a high risk for occlusive vascular diseases. We report 2 cases of renovascular hypertension associated with JAK2 V617F mutation‐positive MPNs and provide a literature review. In Case 1, a 63‐year‐old woman had resistant hypertension, massive proteinuria, and erythrocytosis. Evaluations revealed right renal artery stenosis causing renovascular hypertension and polycythemia vera with JAK2 V617F mutation. Renin‐angiotensin system inhibitors and subsequent angioplasty controlled the blood pressure and the proteinuria resolved. In Case 2, a 74‐year‐old woman had resistant hypertension and thrombocytosis. Evaluations confirmed left renal artery stenosis and essential thrombocythemia with JAK2 V617F. Angioplasty cured the hypertension. A literature review of 18 cases revealed the following as the most common characteristics of MPN‐associated renovascular hypertension: manifests primarily in women; is associated with untreated polycythemia vera and essential thrombocythemia, concomitant leukocytosis, and JAK2 mutation positivity; and is responsive to angioplasty. This report demonstrates that JAK2 mutation‐positive MPNs are a less common but important underlying cause of adult renovascular hypertension.     

A comparison of qPCR and ddPCR used for quantification of the <Emphasis Type="Italic">JAK2</Emphasis> V617F allele burden in Ph negative MPNs

Philadelphia-negative myeloproliferative neoplasms (MPNs) are a diverse group of diseases whose common feature is the presence of V617F mutation of the JAK2 gene. In the era of novel therapeutic strategies in MPNs, such as JAK-inhibitor therapy, there is a growing need for establishing high sensitive quantitative methods, which can be useful not only at diagnosis but also for monitoring therapeutic outcomes, such as minimal residual disease (MRD). In this study, we compared the qPCR and ddPCR methods and their clinical utility for diagnosis, prognostication, and treatment monitoring of MPNs with JAK2 V617F mutation in 63 MPN patients of which 6 were subjected to ruxolitinib treatment. We show a high conformance between the two methods (correlation coefficient r?=?0.998 (p?<?0.0001)). Our experiments revealed high analytical sensitivity for both tests, suggesting that they are capable of detecting the JAK2 V617F mutation at diagnosis of MPN with a limit of detection (LoD) of 0.12% for qPCR and 0.01% for ddPCR. The alterations of JAK2 V617F allele burden in patients treated with ruxolitinib were measured by both methods with equal accuracy. The results suggest an advantage of ddPCR in monitoring MRD because of allele burdens below the LoD of qPCR. Overall, the clinical utility of qPCR and ddPCR is very high, and both methods could be recommended for the routine detection of the V617F mutation at diagnosis, though ddPCR will probably supersede qPCR in the future due to cost-effectiveness.     

JAK2V617F mutation status and allele burden in classical Ph-negative myeloproliferative neoplasms in Japan

JAK2V617F, a gain-of-function mutation in the tyrosine kinase JAK2, is frequently detected in classical myeloproliferative neoplasms (MPNs). In the present study, we determined the JAK2V617F allele burden in Japanese MPN patients using alternately binding probe competitive-polymerase chain reaction, a highly quantitative method recently developed by our group. Although we observed strong similarities in terms of epidemiological parameters associated with the JAK2V617F allele burden between our cohort and others, we found a higher JAK2V617F allele burden in Japanese polycythemia vera (PV) patients and lower frequencies of thrombosis in Japanese MPN patients compared with previous reports. In addition, despite the presence of high red blood cell counts, some patients bearing the JAK2V617F mutation were not diagnosed as PV, as their hemoglobin values were lower than the WHO PV criterion. In these patients, the JAK2V617F allele burden was strikingly similar to that in PV patients fulfilling the 2008 WHO criteria, suggesting that these patients can be classified as PV. Although isotopic measurement of red cell mass (RCM) is required for definitive diagnosis of PV, our data suggest that precise measurement of the JAK2V617F allele burden may improve the diagnosis of PV when RCM has not been determined.