Propensity for hemorrhage and thrombosis in chronic myeloproliferative disorders

Von Willebrand factor activity levels are influenced by driver mutation status in polycythemia vera and essential thrombocythemia patients with well-controlled platelet counts

Von Willebrand factor ristocetin cofactor (VWF activity) and platelet count (PLT) are negatively correlated in patients with polycythemia vera (PV) and essential thrombocythemia (ET). However, VWF activity does not always normalize upon controlling PLT in those patients. To address this issue, we investigated the correlation between VWF activity and PLT in PV and ET patients. The negative correlation between VWF activity and PLT was stronger in calreticulin mutation-positive (CALR+) ET than in Janus kinase 2 mutation-positive (JAK2+) PV or ET groups. When PLT were maintained at a certain level (<600 × 10⁹ /L), low VWF activity (<50%) was more frequently observed in JAK2+ PV patients than in JAK2+ ET (p=0.013) or CALR+ ET (p=0.013) groups, and in PV and ET patients with ≥50% JAK2+ allele burden than in those with allele burden <50% (p=0.015). High VWF activity (>150%) was more frequent in the JAK2+ ET group than in the CALR+ ET group (p=0.005), and often associated with vasomotor symptoms (p=0.002). This study suggests that some patients with JAK2+ PV or ET have VWF activity outside the standard range even with well-controlled PLT, and that the measurement of VWF activity is useful for assessing the risk of thrombosis and hemorrhage.

The association between coagulopathies such as thrombophilia or rare bleeding disorders with the development of gestational vascular complications

The association between coagulopathies, more specifically thrombophilia, and the development of gestational vascular complications was established in the 1990s. Ever since, huge efforts have been invested into gaining a better understanding of the role played by clotting factors, both prothrombotic and hemorrhagic, in those complications, not least because hypertensive disorders and venous thromboembolism are among the most common causes of maternal mortality in the Western world.

Use of Viscoelastography in Malignancy-Associated Coagulopathy and Thrombosis: A Review

The relationship between malignancy and coagulopathy is one that is well documented yet incompletely understood. Clinicians have attempted to quantify the hypercoagulable state produced in various malignancies using common coagulation tests such as prothrombin time, activated partial thromboplastin time, and platelet count; however, due to these tests' focus on individual aspects of coagulation during one specific time point, they have failed to provide clinicians the complete picture of malignancy-associated coagulopathy (MAC). Viscoelastic tests (VETs), such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM), are whole blood analyses that have the advantage of providing information related to the cumulative effects of plasma clotting factors, platelets, leukocytes, and red cells during all stages of the coagulation and fibrinolytic processes. VETs have gained popularity in the care of trauma patients to objectively measure trauma-induced coagulopathy (TIC), but the utility of VETs remains yet unrealized in many other medical specialties. The authors discuss the similarities and differences between TIC and MAC, and propose a mechanism for the hypercoagulable state of MAC that revolves around the thrombomodulin-thrombin complex as it switches between activating the protein C anticoagulation pathway or the thrombin activatable fibrinolysis inhibitor coagulation pathway. Additionally, they review the current literature on the use of TEG and ROTEM in patients with various malignancies. Although limited research is currently available, early results demonstrate the utility of both TEG and ROTEM in the prediction of hypercoagulable states and thromboembolic complications in oncologic patients.

Hemostatic disorders in a JAK2V617F-driven mouse model of myeloproliferative neoplasm

Thrombosis is common in patients suffering from myeloproliferative neoplasm (MPN), whereas bleeding is less frequent. JAK2(V617F), the main mutation involved in MPN, is considered as a risk factor for thrombosis, although the direct link between the mutation and hemostatic disorders is not strictly established. We investigated this question using conditional JAK2(V617F) knock-in mice with constitutive and inducible expression of JAK2(V617F) in hematopoietic cells, which develop a polycythemia vera (PV)-like disorder evolving into myelofibrosis. In vitro, thrombosis was markedly impaired with an 80% decrease in platelet-covered surface, when JAK2(V617F) blood was perfused at arterial shear over collagen. JAK2(V617F) platelets presented only a moderate glycoprotein (GP) VI deficiency not responsible for the defective platelet accumulation. In contrast, a decreased proportion of high-molecular-weight von Willebrand factor multimers could reduce platelet adhesion. Accordingly, the tail bleeding time was prolonged. In the FeCl3-induced thrombosis model, platelet aggregates formed rapidly but were highly unstable. Interestingly, vessels were considerably dilated. Thus, mice developing PV secondary to constitutive JAK2(V617F) expression exhibit a bleeding tendency combined with the accelerated formation of unstable clots, reminiscent of observations made in patients. Hemostatic defects were not concomitant with the induction of JAK2(V617F) expression, suggesting they were not directly caused by the mutation but were rather the consequence of perturbations in blood and vessel homeostasis.

Outcome of patients with splanchnic venous thrombosis presenting without overt MPN: a role for the JAK2 V617F mutation re-evaluation

INTRODUCTION

Although investigation for JAK2 V617F mutation is recommended in patients presenting with splanchnic venous thrombosis (SVT), no specific clinical advice is given to SVT patients presenting without myeloproliferative neoplasms (MPN) and JAK2 V617F mutation. In MPN-free SVT patients, to investigate the clinical outcome, the clinical impact of re-evaluation for the JAK2 V617F mutation, and relationships with the occurrence and time to diagnosis of MPN.

MATERIALS AND METHODS

A cohort of non-cirrhotic SVT patients, enrolled at a single centre and prospectively analyzed.

RESULTS

In 121 SVT patients prospectively followed from 1994 to 2012, a MPN was present in 28 (23.1%). Additional 13 patients (10.7%) showed only the JAK2 V617F mutation. During the follow-up, the JAK2 V617F mutation and/or MPN were identified in 8 patients (median time of development: 21 months, range 6-120), whereas 72 remained (MPN and JAK2 V617F)-free until the end of the observation. The mortality rate was higher among patients presenting with MPN and/or the JAK2 V617F mutation than in patients who developed later or remained disease-free (p=0.032). The thrombosis-free survival was lower in patients with (p=0.04) or developing later MPN and the JAK2 V617F mutation (p=0.005) than in patients (MPN and JAK2 V617F)-free. The incidence of bleeding was similar among groups.

CONCLUSIONS

MPN with or without circulating positive clones for JAK2 V617F mutation can occur long after a SVT, identifying at risk patients for new thrombotic events. If confirmed in other studies, re-evaluation for JAK2 V617F mutation may be of help in early MPN detection and clinical management of SVT patients.

Myeloproliferative disorders and the hyperviscosity syndrome

Myeloproliferative disorders and the serum hyperviscosity syndrome can rapidly manifest with emergent presentations. Hyperviscosity occurs from pathologic elevations of either the cellular or acellular (protein) fractions of the circulating blood. Classic hyperviscosity syndrome presents with the triad of bleeding diathesis, visual disturbances, and focal neurologic signs. Emergency medicine providers should be aware of these conditions and be prepared to rapidly initiate supportive and early definitive management, including plasma exchange and apharesis. Early consultation with a hematologist is essential to managing these complex patients.

The prevalence of the activating JAK2 tyrosine kinase mutation in chronic porto-splenomesenteric venous thrombosis

BACKGROUND

Occult myeloproliferative disorders (MPD) are present in 25% of patients with chronic portal, splenic and mesenteric venous thrombosis (PSMVT). A somatic mutation of JAK2 (JAK2V617F) can be used to identify patients with latent MPD.

AIM

We evaluated the prevalence and clinical significance of JAK2V617F in patients with chronic PSMVT.

METHODS

Allele-specific polymerase chain reaction was performed to screen for JAK2V617F.

RESULTS

Thirty-five patients were tested for JAK2V617F. The underlying pro-coagulant condition was MPD in seven of 35 (20.0%) patients; other aetiologies included hereditary thrombophilia (n = 5), chronic pancreatitis (n = 2), liver abscess (n = 1) and umbilical vein sepsis (n = 3). The remainder were labelled idiopathic, i.e. 17/35 (48.6%) patients. JAK2V617F was detected in 16/35 (45.7%) patients: seven of seven (100%) with MPD, two of 11 (18.1%) with non-MPD acquired conditions and seven of 17 (41.2%) with 'idiopathic' chronic PSMVT. Mean haemoglobin concentration (P = 0.04), haematocrit (P = 0.04), white cell count (P = 0.002) and platelet count (P = 0.05) were significantly higher in patients with JAK2V617F. None of the seven patients with latent MPD have progressed to overt MPD over median follow-up of 85 months.

CONCLUSION

JAK2V617F occurs in 41% of patients with idiopathic chronic portal, splenic and mesenteric venous thrombosis, confirming the presence of latent myeloproliferative disorders, and should form part of the routine pro-coagulant screen.

Recommended timing for surveillance ultrasonography to diagnose portal splenic vein thrombosis after laparoscopic splenectomy

BACKGROUND

Symptomatic portal or splenic vein thrombosis (PSVT) is a rare but potentially lethal complication of laparoscopic splenectomy (LS). While routine postoperative duplex ultrasound surveillance can be used for early detection, the optimal timing is unknown. The aim of this study is to investigate the incidence and progression of asymptomatic PSVT 1 week and 1 month after LS.

METHODS

Consecutive patients scheduled for LS for hematologic disease participated in this study. Patients underwent surveillance for PSVT using duplex ultrasonography 1 week and 1 month postoperatively.

RESULTS

43 of 48 patients planning to undergo LS in the study period were enrolled, with 3 subsequently excluded, leaving 40 for further analysis. The indications for LS were benign disease in 31 [19 had immune thrombocytopenia purpura (ITP)] and malignant disease in 9. A hand-assisted technique was used in 12 cases. PSVT was diagnosed in 9/40 patients (22.5%). Seven (77.8%) were diagnosed by 1 week with ultrasound, of whom one had mild symptoms (fever and diarrhea). After anticoagulation, subsequent ultrasounds showed resolution or improvement in all seven patients. Thirty-three patients had a normal ultrasound result at 1 week. One of these patients also had a computed tomography (CT) scan that found a PSVT not seen on ultrasound. Twenty-seven patients returned for follow-up after normal 1-week imaging: 26 patients had an ultrasound at 1 month, with no new PSVT found. One additional patient did not return for subsequent ultrasound until 2 months later, when a new distal SVT was found; ultrasound at 6 months showed complete resolution without treatment.

CONCLUSION

The 1-week incidence of PSVT after LS was 8/40 (20%). The high incidence justifies ultrasonographic screening on postoperative day 7. If asymptomatic PSVT has not developed at this time, it is unlikely to develop by 1 month, and subsequent screening ultrasound at 1 month is not required.

The JAK2 V617F mutation frequently occurs in patients with portal and mesenteric venous thrombosis

BACKGROUND

Myeloproliferative disorders (MPDs) represent a risk factor for thrombosis in the portal, mesenteric, and hepatic districts.

OBJECTIVE

We aimed to assess whether the Janus kinase 2 (JAK2) V617F mutation, an acquired mutation that occurs in MPD patients, is a risk factor for portal and mesenteric venous thrombosis (PMVT) independently of the presence of overt MPDs.

PATIENTS AND METHODS

The medical histories of 99 patients presenting with PMVT were obtained. The presence of the JAK2 V617F and VHL 598C > T mutations was determined by polymerase chain reaction followed by restriction enzyme analysis and direct cycle sequence analysis.

RESULTS

Over a 10-year period of observation, of the 99 patients presenting with PMVT, the JAK2 V617F mutation was detected in heterozygous state in 17 individuals [17.2%; 95% confidence interval (95% CI) 10.9-25.9]. None of the patients presenting with the JAK2 V617F mutation carried an inherited thrombophilic risk factor. Seven patients with (43.8%; 95% CI 19.8-70.1) and two without (2.4%; 95% CI 0.3-8.4) the JAK2 V617F mutation had a diagnosis of MPD at the occurrence of the venous thrombotic event. After a median follow-up of 41 months (range 3-114 months), three out of the 10 patients carrying the JAK2 V617F mutation were then diagnosed as having idiopathic myelofibrosis (n = 2) or polycythemia vera (n = 1), whereas in seven patients a MPD was not detected. Two of the 83 patients without the JAK2 V617F mutation went on to develop MPDs.

CONCLUSIONS

Determination of the JAK2 V617F mutation may contribute to the search for genetic determinants of PMVT and may be useful to recognize patients who should be carefully observed for the subsequent development of overt MPDs.

Portal vein thrombosis is a common complication following splenectomy in patients with malignant haematological diseases

BACKGROUND

Elective laparoscopic splenectomy (LS) is performed with increasing frequency rather than open splenectomy (OS) because of reduced morbidity. LS is feasible also in patients with haematological diseases with splenomegaly, a group that is subject to more postoperative complications, such as bleeding, infections and portal vein thrombosis (PVT).

METHOD

We retrospectively reviewed the medical records of 69 patients splenectomised for haematological diseases during a 5-yr period at a single centre with the aim of comparing the results and complications after LS and OS.

RESULTS

Thirty-nine patients underwent LS and 30 OS. The median durations of surgery were 138 and 115 min (ns) in the LS and OS groups respectively. Three conversions (7.7%) from laparoscopic surgery to open surgery were necessary because of bleeding and/or splenomegaly. Thromboembolic complications occurred in totally seven of 69 patients. PVT was diagnosed in five of 37 (13.5%) patients with haematological malignancies (three with indolent lymphoma and two with myeloproliferative disease), one after LS and four after OS. All patients with PVT had splenomegaly and had received thromboembolic prophylaxis with low-molecular-weight heparin of short duration. Two patients were diagnosed with deep vein thromboses in the lower leg. Both had idiopathic thrombocytopenic purpura (ITP) and LS.

CONCLUSIONS

Patients with malignant haematological diseases and splenomegaly seem to have a high risk of developing PVT after splenectomy why careful observation and prolonged thromboprophylaxis is recommended for these patients. Ultrasonography or computerised tomography should be considered in all patients with abdominal symptoms after splenectomy.

Use of whole blood platelet lumi-aggregometry to optimize anti-platelet therapy in patients with chronic myeloproliferative disorders

Twenty-seven patients with chronic myeloproliferative disorders and in vitro evidence of platelet hyperactivity on whole blood platelet lumi-aggregometry were commenced on anti-platelet therapy comprising aspirin, clopidogrel, and/or odorless garlic and the studies were repeated to assess the efficacy of the therapeutic agent(s). Only 8 patients showed clear evidence of anti-platelet effect while receiving the standard low-dose (100 mg/day) aspirin therapy. Thirteen patients required a higher dosage of aspirin and/or an additional anti-platelet agent to achieve therapeutic adequacy. Lumi-aggregometry also proved useful to optimize therapy in the 6 patients who received clopidogrel or odorless garlic because of aspirin intolerance.

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.

Thrombotic complications in essential thrombocythemia (ET): clinical facts and biochemical riddles

Hemostatic complications which can occur in the arterial or venous vasculature or in the microcirculation are the major causes of morbidity and mortality in patients with ET. In order to prevent these complications, often platelet reductive drugs are used. These agents are by themselves potentially toxic, i.e. may cause leukemia or cardiac side effects. In order to avoid these adverse effects, a better understanding of the mechanism of thrombus formation which is causative in ET is mandatory. Unfortunately, until now, no biomarkers have been identified which allow the estimation of the risk of thrombotic complications. Platelet number is not a good predictor per se since thrombotic complications can occur in some patients at low platelet numbers whereas others do not encounter a thrombosis even at very high platelet levels. On the other hand, lowering of the platelet count usually results in symptomatic improvement. In ET, morphological alterations of the megakaryocyte in the bone marrow and the circulating platelets are observed: megakaryocyte nuclei show a staghorn appearance, circulating platelets are characterized by anisocytosis and giant size. Functional studies indicate that these anatomically altered platelets function abnormally. When platelets are analyzed with a platelet function analyzer (PFA-100, which uses cartridges that measure how well a patient's platelets adhere and aggregate to form a platelet plug in the first phase of thrombus formation), in many patients with ET, closure time using collagen/ADP and collagen/epinephrine cartridges is prolonged. This seems paradoxical since these patients do not show an increased bleeding time. These results indicate that either receptors and/or consecutive signaling events are abnormal in ET platelets. Proteomic analysis of platelets of ET patients has revealed individual differences but not yet led to the identification of disease-specific proteins. Moreover, the search for alternative risk factors (factor V Leiden, prothrombin gene polymorphism, etc.) has not provided evidence for the contribution of these factors to the generation of the thrombotic risk in ET patients. In summary, despite intensive research over several decades, relatively little is known about the pathogenesis and risk factors for thrombosis in ET. I expect that this conference will contribute to the development of new strategies to identify patients at risk for hemostatic complications.

Condylar resorption following temporomandibular joint arthroscopy in a patient with essential thrombocythemia

Condylar resorption of the temporomandibular joint (TMJ) is a poorly understood phenomenon that is the subject of much controversy. The following case report depicts a unique case of condylar resorption (CR) in a 49-year-old female patient with essential thrombocythemia who underwent arthrocentesis of the TMJ. The exact cause of the CR is unclear but it is speculated that it was likely due to hemorrhagic and thrombotic complications during surgery secondary to an elevated platelet count.

Ex vivo evaluation of erythrocytosis-enhanced platelet thrombus formation using the cone and plate(let) analyzer: effect of platelet antagonists

Red blood cells (RBC) contribute significantly to haemostasis and thrombosis under oscillatory flow conditions, and erythrocytosis has been associated with increased thrombotic risk. To measure the dynamic influences of RBC on platelets, we used a recently described cone and plate(let) analyzer (CPA), evaluating the effect of haematocrit (Hct) on platelet function in whole blood under arterial flow conditions (1800/s, 2 min, 25 degrees C). Anticoagulated blood, reconstituted to varying haematocrits with autologous RBC, demonstrated a significant increase in adherent platelet aggregate formation at Hct levels >45%. This increase was not affected by pretreatment of blood with 0.05 mmol/l aspirin, but was prevented by antagonists of P2Y1, P2Y12, or P2X1, ADP and ATP receptors, and by converting exogenous ADP to ATP with creatine phosphate/creatine phosphokinase. As negligible platelet granule secretion was measured during CPA analysis, but metabolic inhibition of RBC with sodium azide or glutaraldehyde fixation inhibited erythrocytosis-enhanced increases in platelet aggregate size, adenine nucleotides contributing to shear-induced platelet aggregate formation appear to be derived from erythrocytes. These findings support the use of CPA for ex vivo evaluation of the contribution of RBC to platelet function and its inhibition under physiological shear conditions.

PRV-1 , erythroid colonies and platelet Mpl are unrelated to thrombosis in essential thrombocythaemia

Females with the monoclonal type of essential thrombocythaemia (ET), based on the X-chromosome inactivation pattern (XCIP), have previously been shown to present a higher incidence of thrombosis than polyclonal ones. We aimed to assess correlations between XCIP, thrombosis, and three epigenetic markers of ET, namely PRV-1 overexpression, endogenous erythroid colony (EEC) formation, and reduced platelet Mpl content. Fifty-three (60%) of 88 subjects studied had monoclonal myelopoiesis and presented a 32% incidence of major thrombosis compared with 6% of polyclonal subjects (P = 0.009). The frequency of abnormalities of PRV-1, EEC, or Mpl was similar in monoclonal and polyclonal subjects (respectively, 28%, 48%, 75%, and 37%, 27%, 63%), and none of them correlated with thrombosis. We conclude that the exploited epigenetic markers constitute independent phenotypic variations and are not clustered according to monoclonality of myelopoiesis in ET; none of them could serve as a surrogate marker of thrombotic risk in male subjects with ET.