A prospective study of haemostatic parameters in relation to the clinical course of myeloproliferative disorders

Prospective evaluation of variables affecting platelet function in patients with newly diagnosed chronic myeloid leukemia

: Platelet function in chronic myeloid leukemia (CML) could be affected by either hyperleucocytosis, clonal megakaryopoiesis, or tyrosine kinase inhibitors. However, these variables have never been prospectively evaluated. We conducted a prospective study over a period of 1.5 years in a tertiary care center of north India. Patients with CML in chronic phase, more than 18 years, and treated with imatinib were enrolled (n = 32). Age, and sex-matched controls were also included. Platelet function test was performed using two-channel Chrono-Log aggregometer 490 at four time-points: first, at diagnosis; second, after leucoreduction (total leucocyte count, <10 × 10/l) achieved with hydroxycarbamide; third, on-imatinib at BCR-ABL less than 1%; and fourth, in an independent cohort (off-imatinib) at deep molecular response (DMR) (BCR-ABL < 0.01%). Statistical analysis was performed using IBM SPSS statistics (version 22.0). Median age of patients was 42 years (15-65), and M : F ratio was 1 : 1. At diagnosis, platelet function correlated negatively with total leucocyte count, but not with platelet count. As compared with baseline, platelet aggregation with ADP (2.5 μl), and collagen (2.5 μl) improved significantly after leucoreduction (P = 0.05 and 0.009, respectively). Imatinib further caused significant impairment of aggregation with ADP (2.5 μl), collagen (2.5 μl), and collagen (1 μl) (P = 0.04, 0.008, and 0.02, respectively). Patients in DMR also demonstrated a significant impairment of platelet aggregation with all the agonists as compared with controls. While leucoreduction alone can improve the baseline platelet function derangement in CML, imatinib further impairs it. Residual CML stem cells, or effect of imatinib on normal common myeloid progenitors might account for platelet function derangement at DMR.

Do we need antiplatelet therapy in thrombocytosis? Contra. Proposal for an individualized risk-adapted treatment

Thrombocytosis is a frequent laboratory finding but not a diagnosis. Therefore, elevated platelet counts (>450 x 10⁹/l) require careful diagnostic work-up to differentiate between reactive thrombocytosis (RT), caused by various conditions, and essential thrombocythemia (ET), a myeloproliferative neoplasm (MPN). In either setting, aspirin is widely used in clinical practice. However, RT (even at platelet counts >1000 x 10⁹/l) has never been shown to cause thrombosis or bleeding due to acquired von Willebrand factor defects in association with high platelet counts. Identification of reactive conditions and appropriate therapy of the underlying disorder are most relevant. By contrast to RT, ET and related MPN can be associated with thrombosis and/or hemorrhage. Current recommendations suggest the use of low-dose aspirin in all patients with ET unless contraindicated. However, the strength of this recommendation is weak, i. e. evidence level IIb grade B. A potential benefit of aspirin used for primary thromboprophylaxis in ET is mostly derived from the ECLAP study in polycythemia vera (PV). However, translating study results from PV to ET appears to be highly questionable and may be biased. In the absence of robust data regarding the benefit-risk balance of aspirin in ET, it appears reasonable (1) to stratify patients according to their individual thrombotic and bleeding risk, (2) to restrict the use of aspirin to high-risk categories and patients with microcirculatory disturbances, (3) to test for pharmacological efficacy (COX-1 inhibition; measurement of TXB₂), and (4) to modify the aspirin dosing regimen (twice instead of once daily) if required.

Obstetric Complications and Management in Chronic Myeloid Leukemia

Chronic myeloid leukaemia (CML) is amongst the most common haematological malignancies encountered in adults. The younger age of onset and increased incidence of CML in Indians leads to higher chances of encountering it in pregnancy. Pregnancy in CML is a complex situation as first line therapy with tyrosine kinase inhibitors (TKI), is fraught with multiple fetal safety issues. The fetal aspects have been elucidated in literature, but there is scarcity of information on the obstetric outcome per se in presence of CML, excluding the influence of TKI. Obstetric outcomes of 5 pregnancies in four patients with CML are being reported. Literature on interplay of CML and bleeding or thrombotic manifestations is reviewed. The major complications encountered were antepartum (APH) and postpartum haemorrhage (PPH), preterm labour, intrauterine growth retardation and intrauterine fetal death. Patients in the reproductive age group with diagnosis of CML should be carefully counseled regarding the effect of disease and TKI on the maternal-fetal health. Bleeding complications, particularly APH and PPH may be encountered in CML patients. Close coordination of the obstetrician, haematologist, and neonatologist is required in managing these cases successfully. The need for absolute contraception till the remission of disease needs to be emphasized for further pregnancies.

Acquired von Willebrand syndrome in a case of polycythemia vera resulting in recurrent and massive bleeding events in the pleural and abdominal cavity

A 52-year-old woman was admitted to the hospital three times in a span of 5 years in hypovolemic shock because of spontaneous and massive bleeding in the pleural and abdominal cavity. Blood tests revealed a high number of blood cells, and bone marrow smears showed trilineage myeloproliferation. Serum erythropoietin level was decreased. Analysis revealed a V617F mutation in the JAK2 protein. Her activated partial thromboplastin time was slightly prolonged, the ratio between von Willebrand factor (vWF) propeptide and vWF antigen was in the normal range, but the ratio between vWF and ristocetin cofactor was decreased dramatically. Further investigation revealed the absence of large and intermediate vWF-multimers. She was diagnosed with polycythemia vera with acquired von Willebrand syndrome. The bleeding was stopped using a transfusion of freshly thawed plasma and cryoprecipitate.

Platelet Dysfunction in Patients with Chronic Myeloid Leukemia: Does Imatinib Mesylate Improve It?

Objective:

The aim of this study was to investigate the effects of imatinib mesylate on platelet aggregation and adenosine triphosphate (ATP) release in chronic myeloid leukemia patients.

Materials and Methods:

Platelet aggregation and ATP release induced by 5.0 mM adenosine diphosphate, 0.5 mM arachidonic acid, 1.0 mg/mL ristocetin, and 2 µg/mL collagen were studied by whole blood platelet lumi-aggregometer in 20 newly diagnosed chronic myeloid leukemia patients before and after imatinib mesylate treatment.

Results:

At the time of diagnosis, 17/20 patients had abnormal platelet aggregation results; 8 (40%) had hypoactivity, 6 (30%) had hyperactivity, and 3 (15%) had mixed hypo- and hyperactivity. Repeat platelet aggregation studies were performed after a mean of 19 months (min: 5 months-max: 35 months) in all patients who received imatinib mesylate during this period. After therapy, 18/20 (90%) patients had abnormal laboratory results; 12 (60%) had hypoactive platelets, 4 (20%) had mixed hypo- and hyperactive platelets, and 2 (10%) had hyperactive platelets. Three of the 8 patients with initial hypoactivity remained hypoactive, while 2 developed a mixed picture, 2 became hyperactive, and 1 normalized. Of the 6 patients with initial hyperactivity, 4 became hypoactive and 2 developed a mixed pattern. All of the 3 patients with initial hypo- and hyperactivity became hypoactive. Finally, 2 of the 3 patients with initial normal platelets became hypoactive while 1 remained normal. There was a significant decrease in ristocetin-induced platelet aggregation after therapy (p<0.001), while platelet aggregation and secretion induced by other agonists showed no difference after treatment (p>0.05).

Conclusion:

These findings indicate that a significant proportion of chronic myeloid leukemia patients have different patterns of platelet function abnormalities and imatinib mesylate has no effect on these abnormalities, with a significant impairment in ristocetin-induced platelet aggregation.

Normal platelet counts mask abnormal thrombopoiesis in patients with chronic myeloid leukemia

Increased platelet heterogeneity has been reported in myeloproliferative neoplasms (MPN) with thrombocytosis. However, whether abnormal thrombopoiesis occurs in patients with chronic myeloid leukemia (CML) who have normal platelet counts, remains unclear. In order to explore this question, 25 patients with CML with normal platelet counts (CML-N), 40 patients with CML with elevated platelet counts (CML-E) and 33 healthy adults were recruited. The association of platelet count with mean platelet volume (MPV), platelet large cell ratio (P-LCR) and platelet distribution width (PDW) was examined. Bone marrow smears were also reviewed to assess the proliferation and abnormal lobation of megakaryocytes. The results showed that the two CML groups exhibited higher MPV, P-LCR and PDW values than those of the controls (P<0.05). Furthermore, the CML-N group was more heterogeneous in terms of thrombopoiesis than the CML-E group, as demonstrated by a higher PDW (P<0.05) and higher ratio of multinucleated dysmegakaryocytes (12.17 vs. 4.69%; χ²=29.79; P=0.000). In addition, no correlation between platelet count and MPV, P-LCR or PDW was observed in the CML-N group (r=-0.102, -0.051 and -0.049, and P=0.619, 0.828 and 0.810, respectively). The results suggested that patients in the CML-N group have more heterogeneous thrombopoiesis of megakaryocytes and platelets, and that apparently normal platelet counts may mask the abnormal thrombopoiesis in these patients.

Target hematologic values in the management of essential thrombocythemia and polycythemia vera

Treatment of essential thrombocythemia (ET) and polycythemia vera (PV) is aimed at preventing vascular complications, which are the main cause of morbidity and mortality in these diseases. Over the years, clinical trials have demonstrated that the incidence of thrombosis and bleeding can be reduced by controlling the blood cell counts, but the target hematological levels have varied across the studies. In this article, we review the evidence supporting the use of predefined target hematologic values for the management of ET and PV in routine clinical practice. At present, the recommended target hematocrit in PV is below 45%, regardless of the patients' risk profile. Concerning platelet counts, no direct correlation has been demonstrated with thrombotic risk in either ET or PV. Thus, although cytoreductive treatment reduces the rate of vascular complications in high-risk patients, no particular threshold of the platelet counts has been shown to be more protective against thrombosis. Extreme thrombocytosis is a risk factor for bleeding, particularly when aspirin or anagrelide are given. Leukocytosis at baseline or during follow-up appears to be a risk factor for thrombosis, mostly in high-risk patients. However, the clinical benefit of strictly controlling this parameter is not yet established. Finally, standardized definitions of response to cytoreductive treatment in ET and PV have recently been published. Nevertheless, they have been produced to compare the efficacy of new therapies in clinical trials, whereas its relevance in clinical practice has been questioned in retrospective studies showing that such response definitions do not correlate with the patients' clinical outcome.

Polycythemia vera and essential thrombocythemia: 2013 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Polycythemia Vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms (MPN) primarily characterized by erythrocytosis and thrombocytosis, respectively. Other disease features include leukocytosis, splenomegaly, thrombohemorrhagic complications, vasomotor disturbances, pruritus and a small risk of disease progression into acute myeloid leukemia or myelofibrosis.

DIAGNOSIS

Almost all patients with PV harbor a JAK2 mutation. When PV is suspected, the presence of a JAK2 mutation highly suggests the diagnosis and its absence, combined with normal or increased serum erythropoietin level, excludes the diagnosis. Differential diagnosis of ET should include reactive thrombocytosis, chronic myeloid leukemia, prefibrotic myelofibrosis and RARS-T (refractory anemia with ring sideroblasts associated with marked thrombocytosis). A JAK2 mutation is found in 50-70% of patients with ET, myelofibrosis or RARS-T and is capable of distinguishing reactive from clonal thrombocytosis.

RISK STRATIFICATION

Current risk stratification in PV and ET is designed to estimate the likelihood of thrombotic complications: high-risk is defined by the presence of age >60 years or presence of thrombosis history; low-risk is defined by the absence of both of these two risk factors. Recent data considers JAK2V617F and cardiovascular (CV) risk factors as additional risk factors for thrombosis. Presence of extreme thrombocytosis (platelet count >1,000 × 10(9) /L) might be associated with acquired von Willebrand syndrome (AvWS) and, therefore, risk of bleeding. Risk factors for shortened survival in both PV and ET include advanced age, leukocytosis, and history of thrombosis.

RISK-ADAPTED THERAPY

Survival is near-normal in ET and reasonably long in PV. The 10-year risk of leukemic/fibrotic transformation is <1%/1% in ET and <3%/10% in PV. In contrast, the risk of thrombosis exceeds 20%. The main goal of therapy is therefore to prevent thrombohemorrhagic complications. In low risk patients, this is effectively and safely accomplished by the use of low-dose aspirin in both PV and ET and phlebotomy (hematocrit target of <45%) in PV. In high risk patients, treatment with hydroxyurea is additionally recommended, although not mandated in older patients without JAK2V617F or CV risk factors. Treatment with busulfan or interferon-α is usually effective in hydroxyurea failures. Screening for clinically significant AvWS is recommended before administrating aspirin in the presence of extreme thrombocytosis.

Polycythemia vera and essential thrombocythemia: 2012 update on diagnosis, risk stratification, and management

DISEASE OVERVIEW

Polycythemia vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms primarily characterized by erythrocytosis and thrombocytosis, respectively. Other disease features include leukocytosis, splenomegaly, thrombohemorrhagic complications, vasomotor disturbances, pruritus, and a small risk of disease progression into acute myeloid leukemia or myelofibrosis.

DIAGNOSIS

Almost all patients with PV harbor a JAK2 mutation. When PV is suspected, the presence of a JAK2 mutation confirms the diagnosis and its absence, combined with normal or increased serum erythropoietin level, excludes the diagnosis. Differential diagnosis of ET had to include chronic myelogenous leukemia and prefibrotic myelofibrosis. A JAK2 mutation is found in approximately 60% of patients with ET.

RISK STRATIFICATION

Current risk stratification in PV and ET is designed to estimate the likelihood of thrombotic complications: high-risk is defined by the presence of age >60 years or presence of thrombosis history; low-risk is defined by the absence of both of these two risk factors. Presence of extreme thrombocytosis (platelet count >1,000 × 10(9)/L) might be associated with acquired von Willebrand syndrome (AvWS) and, therefore, risk of bleeding. Risk factors for shortened survival in both PV and ET include advanced age, leukocytosis, and history of thrombosis.

RISK-ADAPTED THERAPY

Survival is near-normal in ET and reasonably long in PV. The 10-year risk of leukemic/fibrotic transformation is <1%/1% in ET and <3%/10% in PV. In contrast, the risk of thrombosis exceeds 20%. The main goal of therapy is therefore to prevent thrombohemorrhagic complications and this is effectively and safely accomplished by the use of low-dose aspirin (PV and ET), phlebotomy (PV) and hydroxyurea (high risk PV and ET). Treatment with busulfan or interferon-α is usually effective in hydroxyurea failures. Screening for clinically significant AvWS is recommended before administrating aspirin in the presence of extreme thrombocytosis.

Annual Clinical Updates in Hematological Malignancies: a continuing medical education series: polycythemia vera and essential thrombocythemia: 2011 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Polycythemia vera (PV) and essential thrombocythemia (ET) are myeloproliferative neoplasms primarily characterized by erythrocytosis and thrombocytosis, respectively. Other disease features include leukocytosis, splenomegaly, thrombohemorrhagic complications, vasomotor disturbances, pruritus, and a small risk of disease progression into acute leukemia or myelofibrosis.

DIAGNOSIS

Diagnosis is based on JAK2 mutation status (PV and ET), serum erythropoietin (Epo) level (PV), and bone marrow histopathology (ET). The presence of a JAK2 mutation and subnormal serum Epo level confirm a diagnosis of PV. Differential diagnosis in ET should include chronic myelogenous leukemia and prefibrotic myelofibrosis.

RISK STRATIFICATION

Current risk stratification in PV and ET is designed to estimate the likelihood of thrombotic complications: high-risk-age > 60 years or presence of thrombosis history; low-risk-absence of both of these two risk factors. Presence of extreme thrombocytosis (platelet count > 1,000 x 10⁹/L) might be associated with acquired von Willebrand syndrome (AvWS) and, therefore, risk of bleeding. Risk factors for shortened survival in both PV and ET include age > 60 years, leukocytosis, history of thrombosis, and anemia.

RISK-ADAPTED THERAPY

Survival is near-normal in ET and reasonably long in PV. The 10-year risk of leukemic/fibrotic transformation is < 1%/1% in ET and < 5%/10% in PV. In contrast, the risk of thrombosis exceeds 20%. The main goal of therapy is therefore to prevent thrombohemorrhagic complications and this is effectively and safely accomplished by the use of low-dose aspirin (PV and ET), phlebotomy (PV), and hydroxyurea (high risk PV and ET). Treatment with busulfan or interferon-a is usually effective in hydroxyurea failures.

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.

Thrombosis and haemorrhage in polycythaemia vera and essential thrombocythaemia

Despite decades of clinical and laboratory research, relatively little has been accomplished concerning the pathogenesis as well as the identification of risk factors for thrombosis and bleeding in myeloproliferative disorders. In polycythaemia vera, the pro-thrombotic effect of an elevated haematocrit is well established. In contrast, thrombocytosis per se has not been similarly incriminated in essential thrombocythaemia. In both conditions, advanced age and the presence of a prior event identify thrombosis-prone patients. There is increasing evidence to suggest an additional role by leucocytes that might partly explain the antithrombotic effects of myelosuppressive therapy. A substantial minority of affected patients display reduced levels of high molecular weight von Willebrand protein in the plasma during extreme thrombocytosis and it is believed that this might explain the bleeding diathesis of such patients. Recent controlled studies support the therapeutic value of hydroxyurea and aspirin in essential thrombocythaemia and polycythaemia vera, respectively. The current communication will address the incidence, phenotype, pathogenesis, risk factors, prevention, and treatment of both thrombosis and haemorrhage in these disorders.

The predictive value of megakaryocytic and erythroid colony formation and platelet function tests on the risk of thromboembolic and bleeding complications in essential thrombocythaemia

The predictive value of spontaneous in vitro colony formation of megakaryocytic and erythroid progenitors (154 patients), and defective platelet aggregation responses (55 patients) on the risk of thrombohaemorrhagic complications in patients with essential thrombocythaemia (ET) was evaluated retrospectively. In the in vitro cultures of haematopoietic progenitors, 114/154 patients (74%) showed either spontaneous megakaryocytic or erythroid colony formation or both. Forty-three per cent of patients with any spontaneous colony growth and only 20% of those without this phenomenon had an arterial thrombosis at diagnosis or during the follow-up (P = 0.02). In the whole patient group neither spontaneous megakaryocytic nor spontaneous erythroid colony formation alone predicted the risk of arterial thrombosis. In patients younger than 45 yr of age, the prognostic value of spontaneous megakaryocytic growth was statistically significant: 44% of the patients with spontaneous megakaryocytic colony formation, but only 14% of those without it, experienced arterial thrombosis (P = 0.04). The presence of spontaneous colony formation had no effect on the risk of bleeding complications. Forty-one of the 55 patients (75%) showed abnormalities in the platelet aggregation responses. There was no statistically significant correlation between the platelet function response and the risk of bleeding or thrombotic complications. No correlation was found between the platelet aggregation responses and the presence of spontaneous colony growth. In conclusion, spontaneous colony formation indicated an increased risk of thrombohaemorragic events but the platelet function test had no predictive value for these complications.

Sticky platelet syndrome and thrombocythemia

Platelets are intimately involved in the pathogenesis of thromboembolic disorders, especially arterial forms of thrombosis. Although most arterial thromboses develop on the basis of endothelial injuries, some do not. In these instances "hyperactive" platelets could be the cause. Hyperaggregable platelets have been described in association with a number of acquired disease entities whereby the cause-and-effect relationship is unclear. In contrast, the sticky platelet syndrome is a congenital, autosomal dominant disorder, characterized by hyperaggregable platelets in response to ADP, epinephrine, or both. Patients usually seek treatment for transient or permanent arterial vascular occlusions. These are often precipitated by stressful events. Treatment with low-dose aspirin (81 mg/day) reverses clinical symptoms and hyperaggregability in the laboratory.

Polycythemia vera--a case report and discussion on pathogenic mechanisms of increased thrombosis

Polycythemia vera is a myeloproliferative disorder characterized by increased red cell mass and frequently complicated by venous and arterial thrombosis. The mechanism underlying the increased incidence of thrombotic events remains illusive. Presented in this report are a case of a 77-year-old man diagnosed with polycythemia vera and a review of the current literature on the mechanisms underlying the increased incidence of thrombotic events in polycythemia vera.

Frequent occurrence of anticardiolipin antibodies, Factor V Leiden mutation, and perturbed endothelial function in chronic myeloproliferative disorders

Chronic myeloproliferative disorders (MPD) are characterized by a high incidence of thrombohaemorrhagic complications, possibly related to platelet abnormalities and disturbances of the coagulation system. In an attempt to define abnormalities in coagulation and fibrinolysis, we investigated risk markers for venous thromboembolism, fibrinolytic, and haemostatic system activation markers and antiphospholipid antibodies in blood samples from 50 MPD patients and 30 controls. Compared with controls median levels of protein S free and protein C were significantly decreased in the patients (0.27 vs. 0.38 arbitrary units; P < 0.001 and 0.86 vs. 0.99 arbitrary units; P < 0.001, respectively), and activated partial thromboplastin time was significantly prolonged in patients (33 vs. 27 sec; P < 0.001). No differences were observed in levels of antithrombin, thrombin-antithrombin complex, and fibrin D-dimer. In patients the median value of thrombomodulin was significantly increased indicating perturbed endothelial function. Anticardiolipin antibodies of IgM subtype (median 38 U/mL, 33-99) were detected in 11 patients (22%) and only in one control (3%) (P < 0.021; patients vs. controls). Seven patients were heterozygous for the Factor V Leiden, one patient was heterozygous for the prothrombin G20210A mutation, and one patient was homozygous for the Factor V Leiden mutation. Among controls, two were heterozygous for the Factor V Leiden mutation. Comparing the allele frequency of the Factor V Leiden mutation in patients with MPD and the background population disclosed a significantly increased allele prevalence of the Factor V Leiden mutation in the patients (9% vs. 3.4%; P = 0.003). Alterations in the level of anticoagulant proteins, disturbances of endothelial cell function, and the presence of cardiolipin antibodies and Factor V Leiden mutation may increase the cumulative thrombotic risk in MPD besides the risk imposed by platelet activation.

Abnormalities of platelet aggregation in chronic myeloproliferative disorders

A large variety of platelet dysfunctions has been described in chronic myeloproliferative disorders. These abnormalities may be due to deficiency of platelet granules, arachidonic acid metabolism defects or platelet membrane glycoproteins abnormalities. In this study we intend to detect the incidence of platelet function defects in 76 patients with various types of chronic myeloproliferative disorders. The platelet activity was studied in vitro by measuring platelet aggregation in response to ADP, epinephrine, collagen, arachidonic acid and ristocetin. These results were subsequently correlated with bleeding time and clinical aspects (bleeding or thrombosis). We found complex changes in platelet response with all agonists, in varied proportions. These abnormalities include absent, decreased or abnormal platelet aggregation response. In a few cases we found a markedly decreased, almost absent platelet response to all agonists while in some patients a normal platelet aggregation was noted. The correlation between these results and template bleeding time, thrombotic or hemorrhagic events and the type of diseases was difficult to establish and sometimes conflictual. Despite this fact, we consider that investigating platelet aggregation may be useful not only for the assessment of the hemostatic balance in chronic myeloproliferative disorders but also for a better insight into cell abnormalities occurring in these pathologic conditions.

Avascular necrosis of the femoral head in chronic myeloid leukemia patients treated with interferon-alpha: a synergistic correlation?

BACKGROUND

The objectives of this study were to describe cases of avascular necrosis of the femoral head (ANFH) observed in chronic myeloid leukemia (CML) patients who were treated with interferon-alpha and to review the literature.

METHODS

The authors undertook a case review of the M. D. Anderson experience with ANFH occurring in CML patients who were managed with interferon-alpha-based therapy. MEDLINE (from 1966 to November 1999) and CancerLit (from 1983 to November 1999) searches were conducted to identify cases of avascular necrosis (AVN) associated with either CML or interferon-alpha.

RESULTS

Three patients with ANFH were identified from the authors' experience. No common features related to the disease or therapy were seen among them, except for the presence of thrombocytosis and loss of response. A literature review revealed seven cases of ANFH associated with CML with or without interferon-alpha-based therapy. ANFH was not reported in association with interferon-alpha use for indications other than the treatment of patients with CML.

CONCLUSIONS

ANFH may be the result of an interaction between CML and interferon-alpha therapy. ANFH that occurs in patients with CML who are treated with interferon-alpha should be recognized for treatment implications. Thrombocytosis with consequent microvascular thrombi and avascular necrosis manifesting in susceptible vascular or weight-bearing areas (e.g., the femoral head) may be an associated finding along with loss of response to interferon-alpha therapy.

Increased platelet activation and abnormal membrane glycoprotein content and redistribution in myeloproliferative disorders

Chronic myeloproliferative disorders (MPDs) are characterized by a high incidence of thrombohaemorrhagic complications, possibly caused by platelet dysfunction. In an attempt to define platelet functional abnormalities, we assessed the expression of activation-dependent membrane proteins in unstimulated and agonist [ADP and thrombin receptor-activating peptide (TRAP)]-stimulated platelets using quantitative whole blood flow cytometry in samples from 50 MPD patients and 30 controls. The receptor densities of activation markers and glycoproteins (GPs) were quantified using standardized fluorescent beads. Compared with controls, the mean percentage of P-selectin-positive (15.3% vs. 7.2%; P < 0.001) and thrombospondin (TSP)-positive (6.6% vs. 3.7%; P = 0.003) platelets was increased in unstimulated platelets from patients. Patients having experienced a thrombotic event had a higher mean percentage of TSP-positive non-stimulated platelets than patients without a history of thrombosis (9.0% vs. 4.6%; P = 0.02) and a higher GPIV molecules of equivalent fluorochrome (MEF) value (33113 vs. 24471 MEF; P = 0.02). Mean MEF values of monoclonal antibodies (mAbs) against GPIb (34055 vs. 38945 MEF; P < 0.001) and GPIIb/IIIa (1416 vs. 1648 MEF; P < 0. 001) were significantly reduced among patients, whereas surface expression of GPIV was increased in patients (28273 vs. 16258 MEF; P < 0.001). In TRAP (10 micromol/l) stimulated whole blood, the MEF of P-selectin (9611 vs. 13293 MEF; P = 0.004) and CD63 (2385 vs. 5177 MEF; P < 0.001) and the ratio of PAC-1/GPIIb/IIIa MEF (0.98 vs. 2. 00; P < 0.001) was reduced in patients, indicating either a reduced granule GP content or an intrinsic cellular defect in receptor-mediated granule secretion and activation of the GPIIb/IIIa complex. Expressed as the relative change of MEF compared with unstimulated platelets, TRAP induced decrease of GPIb (7.8% vs. 45%; P < 0.001) and increase of GPIIb/IIIa (49.1% vs. 95.7%; P < 0.001) and GPIV expression (17.8% vs. 55.2%; P < 0.001) was attenuated in patients.

Thrombosis and bleeding in myeloproliferative disorders: identification of at-risk patients with whole blood platelet aggregation studies

Seventy-five patients with chronic myeloproliferative disorders were studied to investigate platelet function by simultaneous measurement of platelet aggregation by the impedance method and ATP dense granule release using a whole blood platelet lumi-aggregometer, in an attempt to identify patients at risk for thrombosis and bleeding. Thirty-nine patients had at least one abnormal result indicating platelet hyperactivity (i.e. impedance or release with one agonist being above the reference range); 16 patients had platelet hypoactivity (i.e. at least one result was below the reference range), whilst 14 had co-existence of hyper- and hypoactivity. Six patients had normal results. 20/53 patients with platelet hyperactivity (alone or mixed) had a positive history of venous and/or arterial thrombosis; in comparison, only two of the other 22 patients had a positive history. During a median follow-up of 33 months, nine patients with and one patient without platelet hyperactivity respectively developed new thrombotic events before the addition of specific therapy. A total of 50 patients with and eight patients without platelet hyperactivity respectively received specific treatment including aspirin and/or cytotoxic therapy. All but one elderly patient with platelet hyperactivity have remained free of new thrombotic events on specific therapy. Two of the 17 patients with platelet hypoactivity had major clinical bleeding. These observations highlight the need to test platelets for hyper- as well as hypo-function and suggest a useful role for routine whole blood platelet aggregation studies to identify the patients at risk for thrombosis or bleeding.

Functional roles of thrombopoietin-c-mpl system in essential thrombocythemia

Thrombopoietin (TPO) is implicated as a primary regulator of megakaryopoiesis and thrombopoiesis through binding to the cytokine receptor c-Mpl (the product of the c-mpl-proto-oncogene). In addition to its physiologic role, the TPO-c-mpl system has been suggested to participate in the pathophysiology of essential thrombocythemia (ET) which is a clonal disorder characterized by a sustained elevation of the circulating platelet count and bone-marrow hyperplasia with excessive proliferation of megakaryocytes. Recent studies have demonstrated that serum TPO levels are slightly elevated or within normal range in ET patients, whereas serum TPO levels tend to be inversely correlated with platelet mass. Flow cytometric, Western blot, and Northern blot analyses have revealed that the expression of platelet c-Mpl is strikingly reduced in all of patients with ET, possibly due to the decreased expression of c-mpl mRNA. These results suggest that normal or slightly elevated levels of serum TPO in ET patients may be attributable to the impaired uptake and catabolism of TPO owing to the low c-Mpl expression. Furthermore, immunoblotting with anti-phosphotyrosine antibody showed that no aberrant protein-tyrosine phosphorylation was observed in platelets of ET patients before treatment with TPO, and the levels of TPO-induced protein-tyrosine phosphorylation, including c-Mpl-tyrosyl phosphorylation, roughly paralleled those of c-Mpl expression, suggesting that c-Mpl-mediated signaling pathway was not constitutively activated in platelets of ET patients. Although activating mutation in the TPO gene, which leads to overexpression of TPO mRNA, has been reported in familial thrombocythemia, these results suggest that TPO-c-Mpl system may not be directly linked to pathogenesis of sporadic ET.

Reduced in vitro clot lysis and release of more active platelet PAI-1 in polycythemia vera and essential thrombocythemia

Because platelets interact with fibrinolysis in a complex manner, it can be expected that with abnormal platelet numbers and quality this interference can be even more profound. The aim of this work was to study the lysis-resistance of platelet-rich clots in diseases with high platelet counts: polycythemia vera (PV), essential thrombocythemia (ET) and to make comparison with polyglobulia (PG). Platelet-rich plasma (PRP) and platelet-poor plasma (PPP) were analyzed by an in vitro clot lysis test. Plasminogen activator inhibitor-1 (PAI-1) activity was measured in plasma and in the supernatants of the washed and gel-filtered platelets after activation by thrombin. The lysis showed decreased speed of PPP-clots in PV and ET. This phenomenon was even more marked in PRP-clots from PV and ET, but further increased lysis resistance after retraction was not observed in PV and ET, most likely due to abnormal platelet functions. Our results suggest that the fibrinolytic activity is reduced in PV and ET, and may play a role both in the increased aptitude for venous thrombosis and in the arterial complications. These are partly caused by higher plasmatic PAI-1 activity as well as by more active platelet PAI-1. The PAI-1 activity was significantly higher in the supernatants of the washed and gel-filtered platelets of PV after activation by thrombin compared with controls. Other factors might have influenced the reduced fibrinolysis.

Markedly Reduced Expression of Platelet c-mpl Receptor in Essential Thrombocythemia

Thrombopoietin (TPO) is implicated as a primary regulator of megakaryopoiesis and thrombopoiesis through binding to the cytokine receptor c-Mpl (the product of the c-mpl proto-oncogene). In an effort to determine the pathophysiological role of TPO-c-Mpl system in essential thrombocythemia (ET), we have examined the levels of serum TPO and the expression and function of platelet c-Mpl in 17 patients with ET. In spite of extreme thrombocytosis, serum TPO levels were slightly elevated or within normal range in most, if not all, patients with ET (mean ± SD, 1.31 ± 1.64 fmol/mL), as compared with normal subjects (0.76 ± 0.21 fmol/mL). Flow cytometric and Western blot analyses revealed that the expression of platelet c-Mpl was strikingly reduced in all patients with ET. Furthermore, the expression of platelet c-mpl mRNA was found to be significantly decreased in the ET patients tested. In contrast, almost identical levels of GPIIb/IIIa protein and mRNA were expressed in platelets from ET patients and normal controls. In addition to expression level, activation state of platelet c-Mpl was investigated in ET patients. Immunoblotting with anti-phosphotyrosine antibody showed that no aberrant protein-tyrosine phosphorylation was observed in platelets of ET patients before treatment with TPO, and the levels of TPO-induced protein-tyrosine phosphorylation, including c-Mpl-tyrosyl phosphorylation, roughly paralleled those of c-Mpl expression, suggesting that c-Mpl–mediated signaling pathway was not constitutively activated in platelets of ET patients. These results suggested that the TPO-c-Mpl system may not be directly linked to pathogenesis of ET, and that gene(s) mutated in ET may be important in regulating the levels of c-mpl gene expression in addition to the growth and differentiation of multipotential hematopoietic stem cells.

Enhanced generation of monocyte tissue factor and increased plasma prothrombin fragment1+2 levels in patients with polycythemia vera: mechanism of activation of blood coagulation

Polycythemia vera (PV) is associated with a high incidence of thrombosis. The association of apparent and secondary polycythemia with thrombosis is not clear. It was suggested that activation of the coagulation system contributes to thrombus formation in PV. However, the mechanism of activation is unknown. Monocytes generate a potent tissue factor (TF) upon stimulation with various substances, which is involved in thrombus formation in various disorders. Therefore, we studied the possibility that the factor is involved in the activation of coagulation and thrombus formation also in PV. Unstimulated peripheral blood mononuclear cells (PBMC) from each of the different types of polycythemia expressed weak TF activity (2 U) and antigen (41.4 to 52.9 pg/ml), which were similar to normal controls. Following stimulation with endotoxin, PBMC from normal controls and from apparent and secondary polycythemia showed a 3.9- to 4.5-fold increase in TF, while cells from PV showed a 21-fold increase (P<0.001). Similar levels were generated by PBMC after treatment of PV and at the spent phase. TF was generated by monocytes but not by lymphocytes. Plasma prothrombin fragment1+2 (F1+2) levels, assayed at the same time, were significantly higher in PV (2.46 nm) compared to normals and apparent and secondary polycythemia (0.22 to 0.32 nm), and were in a significant correlation with monocyte TF activity and antigen levels (r = 0.77, 0.87). The high levels of F1+2 confirm that the coagulation system is activated in PV. The increased capacity of monocytes to generate TF may be responsible for the activation of the coagulation system and thrombus formation. The hypercoagulability state that is induced by this mechanism suggests that long-life oral anticoagulation should be considered once thrombosis has been developed in PV.

Bleeding time and platelet function in essential thrombocythemia and other myeloproliferative syndromes

Bleeding time (BT) and platelet function tests have been widely used in patients with essential thrombocythemia (ET), with the aim to support diagnosis and to identify laboratory predictors of haemorrhagic and thrombotic complications. BT is significantly prolonged in 7-19% of ET patients and several functional abnormalities have been observed in platelet structure, biochemistry and survival. However, the attempt to relate these in vivo and in vitro platelet dysfunctions with diagnosis or clinical sequelae has been generally disappointing. Therefore, BT and platelet function tests are currently not recommended in the initial evaluation or during the follow-up of patients with ET, unless in the setting of a clinical or biological study. A noteworthy exception is represented by a subset of patients characterized by very high platelet count (> 1500 x 10(9)/L) and bleeding symptoms, who can have an acquired von Willebrand disease. In these cases, prolonged BT and abnormal multimeric pattern of von Willebrand factor are useful for diagnosing and monitoring this acquired hemorrhagic disease. BT and platelet function tests should be included in the baseline evaluation of ET patients enrolled in prospective clinical trials aiming assess their predictive role on clinical end-points.

Occlusion of the superior mesenteric artery in a patient with polycythemia vera: resolution with percutaneous transluminal angioplasty

The case is reported of a 46-year-old male patient with polycythemia vera (PV) treated with phlebotomy who developed an occlusive thrombosis of the superior mesenteric artery 2 years after the diagnosis. He was successfully managed with percutaneous transluminal angioplasty. The patient did not develop any other thrombotic phenomena. To our knowledge, there are no previous reports on the use of percutaneous transluminal angioplasty in the management of arterial thrombotic complications in PV patients.

Platelet activation and thrombosis: studies in a patient with essential thrombocythemia

Recent advances permit the detection of activated platelets using specific monoclonal antibodies and flow cytometry. Nevertheless, there are few reports in which activated platelets have been studied over a period of time in patients at risk for thrombosis. Our patient S.D. has essential thrombocythemia and a prothrombotic state manifested in two major thrombotic episodes involving the portal vein and a mesenteric artery. Investigation revealed both spontaneous aggregation and hyperaggregability in response to ADP and the presence of activated platelets in platelet-rich plasma as revealed by flow cytometry. Interestingly, the activated platelets were recognized by an anti-RIBS ("receptor-induced binding site") monoclonal antibody that recognized bound fibrinogen but not by antibodies reactive with antigens whose presence on the platelet surface was secretion dependent. Treatment with aspirin inhibited spontaneous platelet aggregation but had little effect on the activated platelet profile. A change of therapy to ticlopidine suppressed expression of platelet activation markers. Treatment with ticlopidine has continued for 1 year so far without further thrombotic complications.

High plasma levels of plasminogen activator inhibitor 1 (PAI-1) in polycythemia vera and essential thrombocythemia are associated with thrombosis

We attempted to determine if a hypercoagulability state exists in patients with polycythemia vera (PV) and essential thrombocythemia (ET). We studied the hematocrit level, platelet count, use of any antiaggregant drugs, thrombotic or bleeding accidents and plasma levels of antithrombin III, protein C, total protein S, free protein S, vWF:Ag (Von Willebrand's factor related antigen), thrombin-antithrombin complexes, D-dimer, fibrinolytic activity, tissue plasminogen activator, plasminogen and PAI-1 in 33 patients (19 with ET and 14 with PV). PAI-1 plasma concentration was significantly higher in, both ET and PV patients than in the control group, and were higher in those patients with previous thrombotic episodes than in asymptomatic patients or with previous bleeding episodes. Increasing age was associated to more thrombotic episodes while younger patients presented with more hemorrhagic complications. A linear correlation between platelet count and PAI-1 levels in PV patients (r = 0.44, p < 0.05) and ET patients (r = 0.30, p < 0.05) was found. Fibrinolytic activity in patients with ET was significantly decreased when compared to the control group. A hypofibrinolytic state could be an additional factor which could be used as a predictive index of the thrombotic or bleeding tendency in each patient.

Incidence and clinical risk factors for bleeding and thrombotic complications in myeloproliferative disorders. A retrospective analysis of 260 patients

Bleeding and thrombosis are frequent complications in myeloproliferative disorders (MPD) and are associated with severe organ damage and a high mortality. Elevated platelet count, elevated hematocrit, and patient age are regarded as risk factors for bleeding and thromboembolic events in MPD, although the significance of these parameters was not confirmed by clinical studies. We retrospectively analyzed vascular complications in 260 patients with MPD and tried to identify parameters predictive for bleeding and thrombembolic events. Our cohort consisted of 115 patients with chronic myeloid leukemia (CML), 84 patients with polycythemia vera (PV), 26 with essential thrombocythemia (ET), 25 with osteomyelofibrosis (OMF), and 10 patients with unclassifiable MPD. During a median follow-up period of 31 months, 126 patients with chronic MPD suffered bleeding or thrombotic events. Bleeding was observed in 57% of patients with OMF, 23% with PV, 20% with chronic phase CML, and 16% with ET. Thrombotic events were most common in patients with PV (36% of patients), followed by ET, OMF, and chronic phase CML (20%, 17%, and 6% of patients, respectively). Recurrent thrombotic episodes frequently occurred in patients with PV and ET, whereas patients with OMF often had more than one bleeding event. Thirty patients died of thrombohemorrhagic complications during follow-up. Multivariate analysis, including all patients with chronic MPD, revealed that elevated red blood cell count, higher hemoglobin level, and increased percentage of segmented neutrophils at the time of diagnosis were associated with thrombosis, whereas patients with bleeding complications were characterized by low red cell count, lower hemoglobin, and a lower percentage of segmented neutrophils. However, when analyzed by MPD subgroup, none of these parameters retained a predictive value for bleeding or thrombotic events. Moreover, elevated platelet count and patient age were not risk factors for bleeding complications. Thrombotic events were less frequent in patients below the age of 40, and were increased in patients aged 70 and above. However, this was primarily due to the high percentage of elderly patients in subgroups mainly affected by thrombosis (PV and ET). In most MPD subgroups, the rate of bleeding and thrombosis was highest just before and during the first months after diagnosis, and declined thereafter. Thrombohemorrhagic complications were less frequent after phlebotomy in PV and after therapy with alkylating agents in CML. The institution of cytoreductive therapy soon after the diagnosis was made may explain the reduced incidence of complications later in the disease. We conclude that morbidity and mortality from thrombohemorrhagic complications are high in myeloproliferative disorders.(ABSTRACT TRUNCATED AT 400 WORDS)