Quantification of PRV-1 mRNA distinguishes polycythemia vera from secondary erythrocytosis. (41/454)

To date, the diagnosis of polycythemia vera (PV) relies on clinical criteria. We have recently described the overexpression of a hematopoietic receptor, polycythemia rubra vera-1 (PRV-1), in patients with PV. Here, we report a quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay for the measurement of PRV-1 mRNA levels. We have determined PRV-1 expression in 71 patients with PV, 11 patients with secondary erythrocytosis (SE), as well as in 80 healthy controls. PV patients express significantly higher amounts of PRV-1 than healthy controls or patients with SE (P <.0001). Because there is no overlap between the PRV-1 expression in PV patients versus healthy controls or SE patients, the assay has a very high sensitivity and specificity for the diagnosis of PV in our population. In patients with erythrocytosis, the quantitative RT-PCR assay described here therefore provides a rapid, highly specific and sensitive tool for the diagnosis of PV.  (+info)

Allogeneic hematopoietic stem cell transplantation for myelofibrosis. (42/454)

Fifty-six patients, 10 to 66 years of age, with idiopathic myelofibrosis (IMF) or end-stage polycythemia vera or essential thrombocythemia received allogeneic hematopoietic cell transplants from related (n = 36) or unrelated (n = 20) donors. Forty-four patients were prepared with busulfan plus cyclophosphamide and 12 with total body irradiation plus chemotherapy. The source of stem cells was marrow in 33 and peripheral blood in 23 patients. All but 3 patients achieved engraftment. While 50 patients showed complete donor chimerism, 3 patients were found to be mixed chimeras at 26, 48, and 86 months after transplantation, respectively. Two patients died from relapse/progressive disease, and 18 died from other causes. There are 36 patients surviving at 0.5 to 11.6 (median, 2.8) years, for a 3-year Kaplan-Meier estimate of 58% (CI, 43%-73%). Dupriez score, cytogenetic abnormalities, and degree of marrow fibrosis were the most significant risk factors for posttransplantation mortality. Patients conditioned with a regimen of busulfan targeted to plasma levels of 800 to 900 ng/mL plus cyclophosphamide had a higher probability of survival (76% [CI, 62%-91%]) than other patients. Results with unrelated donors were comparable with those with HLA-identical sibling transplants. Thus, allogeneic hematopoietic cell transplantation offers long-term relapse-free survival for patients with myelofibrosis.  (+info)

PTP-MEG2 is activated in polycythemia vera erythroid progenitor cells and is required for growth and expansion of erythroid cells. (43/454)

Polycythemia vera (PV) is a human clonal hematologic disorder. Previously we demonstrated that erythroid colony-forming cells (ECFCs) from PV patients contained a hyperactive membrane-associated tyrosine phosphatase. We now show that this phosphatase corresponded to protein tyrosine phosphatase (PTP)-MEG2, an intracellular enzyme with a putative lipid-binding domain. The increased activity of PTP-MEG2 in PV cells is due to its elevated distribution in the membrane fraction. With the development of ECFCs to mature red cells, the protein level of PTP-MEG2 decreased gradually, but membrane-associated PTP-MEG2 was sustained for a longer period of time in PV cells, which correlated with an enhanced colony-forming capability of the cells. Importantly, expression of dominant-negative mutant forms of PTP-MEG2 suppressed in vitro growth and expansion of both normal and PV ECFCs. The data indicate that PTP-MEG2 has an important role in the development of erythroid cells.  (+info)

Increased thromboxane biosynthesis in patients with polycythemia vera: evidence for aspirin-suppressible platelet activation in vivo. (44/454)

Increased thromboxane (TX) production and modified aspirin sensitivity has been detected in vitro in platelets isolated from patients with polycythemia vera. To verify the relevance of these capacity-related measurements to the actual rate of TXA2 biosynthesis in vivo and its suppression by oral aspirin, we have investigated the urinary excretion of major enzymatic metabolites of TXB2 in 17 patients with polycythemia vera and 23 gender- and age-matched controls. Urinary 11-dehydro-TXB2 and 2,3-dinor-TXB2 were measured by previously validated radioimmunoassays. In addition, urinary immunoreactive leukotriene (LT) E4 was measured to explore the 5-lipoxygenase pathway of arachidonate metabolism. Polycythemic patients had significantly (P < .001) higher excretion rates of both 11-dehydro-TXB2 (1,033 +/- 1,050 v 117 +/- 45 pmol/mmol creatinine; mean +/- SD) and 2,3-dinor-TXB2 (725 +/- 676 v 82 +/- 43 pmol/mmol creatinine) than controls. In contrast, urinary LTE4 was not significantly different. Enhanced metabolite excretion did not correlate with the platelet count or with the hematocrit value, and was not related to the current treatment or to a clinical history of thrombotic complications. Platelet TX receptor studies did not show any significant changes in the binding characteristics of two different ligands. A platelet-selective regimen of aspirin therapy (50 mg/d for 7 to 14 days) was associated with greater than 80% suppression in metabolite excretion in nine patients. These results are consistent with abnormal stimuli operating in polycythemia vera to induce a selective enhancement in the platelet biosynthesis of TXA2 without changes in receptor binding. This in vivo abnormality in platelet biochemistry can be largely suppressed by low doses of aspirin.  (+info)

Polycythaemia vera and Christmas disease with slightly prolonged prothrombin time. (45/454)

A family is reported in which Christmas disease in one member and polycythaemia in another were associated with prolongations of the one-stage prothrombin time of the factor-VII deficiency type. Changes in the prothrombin time were present in the siblings of the case of Christmas disease and in a number of unrelated cases of polycythaemia vera. The use of "mixing procedures" did not reveal any significant mutual correction of the changes in prothrombin time.  (+info)

The myeloproliferative disorders. Current clinical and laboratory considerations. (46/454)

The various hemopoietic and supportive cells of the marrow may proliferate beyond physiologic boundaries in response to a number of stimuli. In certain instances, the stimuli are known, and upon their removal the myeloproliferation returns to normal boundaries. These, the reactive myeloproliferations, are best represented by the leukemoid states and the secondary polycythemias. In other cases, the stimuli responsible for the myeloproliferation remain unknown and the clinical disease ends fatally. These, the neoplastic myeloproliferations, include the granulocytic, monocytic and red cell leukemias, as well as the polycythemia vera and myelofibrosis syndrome. In clinical practice it is important to identify the various myeloproliferative syndromes. This task has been facilitated by cytochemical tests that have recently become available, among which the estimation of the leukocyte alkaline phosphatase (LAP) in peripheral blood is a technically simple and extremely useful example. The LAP is normal in secondary polycythemias and decidedly elevated in polycythemia vera, myelofibrosis and leukemoid states. It is greatly decreased in the granulocytic leukemias.  (+info)

POLYCYTHEMIA VERA: PERIPHERAL VASCULAR MANIFESTATIONS. (47/454)

The presenting manifestations of polycythemia vera are often complications involving the vascular system. These include myocardial infarction, cerebro-vascular accidents and ischemic changes in the extremities.The concept of increased atherogenesis in cases of polycythemia vera has been questioned. A possible mechanism by which small, otherwise subclinical atheromatous plaques produce ischemic symptoms in patients with polycythemia vera is discussed. The blood in polycythemic patients has been shown to have an increased viscosity resulting in a prolonged circulation time. If a small atheromatous plaque is present in association with increased blood viscosity, this combination may well produce ischemic symptoms. This explains why treatment of polycythemia vera, with restoration of blood to normal viscosity, often reverses the patient's ischemic symptoms. Two cases of polycythemia vera here reported, in which the presenting manifestations were gangrenous extremities, emphasize the need for prompt diagnosis and treatment of polycythemia vera. In the first case, early recognition and treatment of polycythemia vera successfully reversed the ischemic changes in the extremities, while failure of early recognition and treatment in the second case resulted in two major amputations.  (+info)

Clinical utility of the absolute number of circulating CD34-positive cells in patients with chronic myeloproliferative disorders. (48/454)

BACKGROUND AND OBJECTIVES: Flow cytometry enumeration of peripheral blood CD34-positive cells provides reliable measurements of circulating hematopoietic progenitors in humans. Since the absolute number of circulating CD34-positive cells has been previously found to be elevated in myelofibrosis with myeloid metaplasia (MMM), we prospectively studied the clinical utility of this parameter in the work-up of patients with chronic myeloproliferative disorders. DESIGN AND METHODS: Of the 248 consecutive patients enrolled in this study, 106 had polycythemia vera (PV), 90 essential thrombocythemia (ET), and 52 myelofibrosis with myeloid metaplasia (MMM). The study population included both newly diagnosed and established cases, and of these latter some patients were on cytoreductive treatment while others were chemotherapy naive. Both cross-sectional and longitudinal investigations were carried out. Flow cytometry enumeration of CD34-positive cells was performed using a single-platform assay. RESULTS: Median numbers and ranges of circulating CD34-positive cells were 2.3x10(6)/L (0-5) in 20 control subjects, 2.2x10(6)/L (0-14) in those with PV, 2.4x10(6)/L (0-14) in those with ET, and 114x10(6)/L (6-2,520) in MMM patients. Analysis of variance demonstrated that values were markedly higher in MMM patients than in the remaining groups, and counts did not appear to fluctuate over short periods of follow-up. In both cross-sectional and longitudinal investigations on patients at clinical onset and/or out of cytoreductive treatment, a CD34-positive count of > or = 15x10(6)/L was always associated with MMM, clearly indicating a disease-related specificity. INTERPRETATION AND CONCLUSIONS: The absolute number of circulating CD34-positive cells is normal or anyhow lower than 15x10(6)/L in patients with uncomplicated PV or ET, whereas it is equal or above this cut-off in those with MMM, likely reflecting abnormal hematopoietic progenitor cell trafficking. Thus, enumeration of circulating CD34-positive cells may be useful in the work-up of patients with myeloproliferative disorders.  (+info)