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PubMed1999

Ehrlich tumor stimulates extramedullar hematopoiesis in mice without secreting identifiable colony-stimulating factors and without engagement of host T cells.

Tumor growth is associated with neutrophilia, thrombocytosis, and extramedullar hematopoiesis. The mechanism(s) accounting for these phenomena is unclear, although granulocyte-macrophage colony-stimulating factor (GM-CSF) and/or granulocyte colony-stimulating factor (G-CSF) released by tumor cells have been involved. We studied whether CSF released by Ehrlich tumor (ET) may play a role. A comparative study was performed with two cell variants (ET and ET/0) growing in euthymic, nude, and SCID mice. Extramedullar hematopoiesis was assessed in the spleen by scoring organ enlargement, wheat germ agglutinin ve+ cells, and interleukin 3-dependent granulocyte-macrophage colony-forming unit (GM-CFU). Both cell lines showed the same cytokine profile by reverse transcriptase polymerase chain reaction, including GM-CSF, G-CSF, and macrophage colony-stimulating factor (M-CSF); yet, only ET cells produced detectable colony-stimulating activity in vitro, mainly due to GM-CSF. No differences in tumorigenicity were noted between ET and ET/0 cells inoculated to normal or immunodeficient mice. An increase in extramedullar hematopoiesis, accompanied by neutrophilia and thrombocytosis, was associated with tumor progression irrespective of the cell line. A strong correlation was obtained between the increase in splenic GM-CFU and tumor mass (r = 0.96, p < 0.0001) that was independent on the tumor cell line, strain of mice, or stage of tumor development. The results point against CSF released by tumor cells and/or reactive host T cells as the only factors involved in the extramedullar hematopoiesis in this tumor model. The remarkable correlation between splenic GM-CFU and the tumor mass still suggests that a factor(s) of tumor origin may play a critical role.

Animals↗
PubMed1996

Thrombotic and hemorrhagic complications in chronic myeloproliferative disorders.

Bleeding and thrombosis are major causes of morbidity and mortality in patients with chronic myeloproliferative disorders. We retrospectively evaluated 101 consecutive patients affected by primary thrombocytosis (46 male, 55 female, aged 18-84 years; mean +/- SD 61 +/- 15) followed for a period ranging from 6 months up to 10 years (median 5 years) at our hematological unit. At the time of diagnosis 48 patients were asymptomatic; 26 had clinical evidence of atherothrombosis (cerebral ischemic attacks, ischemic heart disease, peripheral occlusive arterial disease), ten had venous thrombosis, four experienced major hemorrhages, 23 presented microvascular ischemic manifestations namely erythromelalgia, paresthesias, acrocyanosis and dizziness. At presentation 51.2% of the patients had elevated serum lactic dehydrogenase, 34.5% hyperuricemia, and 23.4% serum creatinine > 1.2 mg/dL. Color Doppler ultrasound provided evidence of vascular stenosis or medium-intimal hyperplasia of epiaortic vessels in 48.9% of patients studied, and similar alterations of lower limb arteries in 23.8% of cases. Therapy modality included an antiplatelet agent (picotamide 300 mg/bid); a cytoreductive agent (busulphan, hydroxyurea, pipobroman or melphalan) was used when platelet count was > 800000/microL. Symptoms due to microvascular ischemia promptly regressed after picotamide and cytoreductive therapy. During follow-up. nine patients suffered from atherothrombotic events (transient ischemic attacks, ischemic stroke, unstable angina pectoris) and five developed deep vein thrombosis or superficial thrombophlebitis. Five patients experienced major hemorrhages (two melena, two hematuria, one perioperative bleeding); the two gastrointestinal hemorrhages occurred in patients self-medicated with non steroidal anti-inflammatory drugs, and the two episodes of hematuria occurred on oral anticoagulant therapy and aspirin respectively. No major bleeding occurred in patients on continuative therapy with picotamide, even in the presence of upper digestive tract disorders. Seven patients died: mortality resulted from one sudden coronary death, three solid neoplasia, one blast crisis, one anile, and one massive hemorrhage due to abdominal aortic prosthesis tearing. Our study suggests that a long-term antithrombotic prophylaxis with picotamide may be of benefit in patients affected by primary thrombocytosis; a controlled clinical trial is warranted to assess whether picotamide can ameliorate the natural history of the disease.

Adolescent↗
PubMed1998

Haematopoietic progenitors and signal transduction in polycythaemia vera and primary thrombocythaemia.

While significant progress has been made in understanding the cellular defect and molecular basis of polycythaemia vera (PV), elucidation of the primary mutation leading to PV remains elusive. While clinically useful, the PV diagnostic criteria put forward by the Polycythemia Vera Study Group are not based on the pathophysiology of this disorder and in some instances may lead to false diagnosis or may not be sufficient to diagnose an early PV. In diagnostically unclear situations, clinical and laboratory findings must take into account the acquired nature of PV, its clonality, and the presence of endogenous erythroid colony formation in serum-containing media. It is likely that other simpler assays may be developed based on the rapidly emerging knowledge of the cellular pathology of PV. Several intriguing observations of abnormalities pertaining to the erythroid signal transduction have been recently reported; these remain to be validated in other laboratories and to be proven specific for PV. The clinical concept of primary thrombocythaemia (PT) lags behind what we know about PV. While the diagnosis of PT is still based on the exclusion of other known causes of thrombocytosis, new knowledge is emerging. Recent clonality studies of a large number of PT females show that the majority are clonal. It is our belief that thrombocythaemic subjects who are not found to be clonal are those with secondary thrombocytosis. Multiple in vitro-based assays of megakaryocytic and erythroid progenitors have been developed and conflicting data published. It is likely that standardized assays of megakaryocytic progenitors will soon become available and a reproducible PT specific defect will be found. Such a specific test would be of immense diagnostic value in this most elusive of all myeloproliferative disorders.

Cells, Cultured↗
PubMed2003

Thrombocythaemia and pregnancy.

The diagnosis of essential thrombocythaemia (ET) is considered when all causes of reactive (secondary) thrombocytosis have been excluded in a patient with a persistent thrombocytosis. Among the chronic myeloproliferative disorders, ET has the highest proportion of young as well as female patients affected. As such, the optimal management of ET during pregnancy becomes an important issue. Although ET is not a contraindication to childbearing, the risks to both the fetus and mother are increased, and would-be-parents should be counselled regarding these. Obstetric complications occurring at higher than expected rates include spontaneous abortion in the first-trimester. Maternal complications, both haemorrhagic and thrombotic, are reported relatively infrequently. It is generally difficult to make specific management recommendations because of the relative rarity of the association between ET and pregnancy, which has precluded adequately powered controlled trials. In this communication, we review our own experience as well as that of other investigators on the subject matter and provide management guidelines that are based on best available information.

Disease Management↗
PubMed1998

Interleukin 6 and its relationship to clinical parameters in patients with malignant pleural mesothelioma.

The relationship between interleukin 6 (IL-6) levels and clinical parameters was studied in 25 patients with malignant pleural mesothelioma. The serum levels of IL-6, C-reactive protein, alpha1-acid glycoprotein and fibrinogen were significantly higher in mesothelioma than in lung adenocarcinoma with cytology-positive pleural effusion. Serum IL-6 levels correlated with the levels of the acute-phase proteins. We demonstrated a high incidence of thrombocytosis (48%) and a significant correlation between platelet count and the serum IL-6 level. The level of IL-6 in the pleural fluid of patients with mesothelioma was significantly higher than in the pleural fluid of patients with adenocarcinoma, and was about 60-1400 times higher than in the serum. However, even higher levels of IL-6 in the pleural fluid and of thrombocytosis were found in patients with tuberculous pleurisy. These results indicate that large amounts of IL-6 from the pleural fluid of patients with mesothelioma leak into the systemic circulation and induce clinical inflammatory reactions. These profiles are not specific to mesothelioma as similar profiles are found in patients with tuberculous pleurisy. However, the detection of a markedly increased level of IL-6 in pleural fluid argues against a diagnosis of adenocarcinoma.

Adenocarcinoma↗
PubMed1999

Platelet number and interleukin-6 correlate with VEGF but not with bFGF serum levels of advanced cancer patients.

We have compared the platelet number and the serum concentration of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and interleukin-6 (IL-6) in 80 blood samples of 50 patients with advanced cancer. We have also measured the mitogenic effect of patient sera on endothelial cells in vitro in order to estimate the biological activity of serum VEGF. Serum VEGF concentration correlated with platelet number (r = 0.61; P < 10(-4)). Serum IL-6 levels correlated with platelet count (r = 0.36; P < 10(-3)), with serum VEGF levels (r = 0.55; P < 10(-4)) and with the calculated load of VEGF per platelet (r = 0.4; P = 3 x 10(-4)). Patients with thrombocytosis had a median VEGF serum concentration which was 3.2 times higher (P < 10(-4)) and a median IL-6 serum level which was 5.8 times higher (P = 0.03) than in other patients. Serum bFGF did not show an association with any of the other parameters. Patient sera with high VEGF and bFGF content stimulated endothelial cell proliferation significantly more than other sera (P = 4 x 10(-3)). These results support the role of platelets in the storage of biologically active VEGF. Platelets seem to prevent circulating VEGF from inducing the development of new blood vessels except at sites where coagulation takes place. IL-6, besides its thrombopoietic effect, also seems to affect the amount of VEGF stored in the platelets. This is in accordance with the indirect angiogenic action of IL-6 reported previously. The interaction of IL-6 with the angiogenic pathways in cancer might explain the stimulation of tumour growth occasionally observed during IL-6 administration. It also conforms to the worse outcome associated with high IL-6 levels and with thrombocytosis in several tumour types and benign angiogenic diseases.

Angiogenesis Inducing Agents↗
PubMed1998

Major effects of TPO delivered by a single injection of a recombinant adenovirus on prevention of septicemia and anemia associated with myelosuppression in mice: risk of sustained expression inducing myelofibrosis due to immunosuppression.

Adenoviral vectors may be useful tools to deliver a cytokine in vivo. A single intravenous injection of an adenovirus vector containing the human thrombopoietin (TPO) cDNA (AdRSVhuTPO) was able to induce a thrombocytosis for more than 6 weeks in SCID mice, associated with a megakaryocyte (MK) hyperplasia in different organs. A marrow and spleen fibrosis was observed at 6 weeks. In immunocompetent mice, a single AdRSVhuTPO injection led to a moderate and transient thrombocytosis without myelofibrosis. To evaluate the usefulness of TPO for the prevention of secondary side-effects during an aplastic period, mice were subjected to a myeloablative regimen 7 days after the intravenous AdRSVhuTPO injection. In this setting, TPO prevented mortality by accelerating hematological recovery. Survival was essentially related to an improvement in the leukopenia since all control mice died from septicemia. However, the effects of TPO may be potentiated by the release of inflammatory cytokines following the adenovirus infection; AdRSV beta galactosidase injected-mice had higher numbers of BFU-E and CFU-GM in the marrow than PBS-injected mice. Myelosuppression induced transient immunosuppression responsible for a sustained expression and elevation of platelet numbers for at least 5 months. These results further suggest that TPO may be an effective therapy in diminishing hematological complications related to myeloablative regimens, but emphasize that immunosuppression secondary to myelosuppression may lead to sustained expression associated with a risk of thrombosis and myelofibrosis when delivered by adenovirus vectors.

Adenoviridae↗
PubMed1996

Acute-phase response and the hypercoagulable state in pulmonary tuberculosis.

In our experience, severe pulmonary tuberculosis (PTB) is often complicated by deep venous thrombosis (DVT). Because of the association between inflammation and haemostatic changes that can result in a hypercoagulable state, we have prospectively examined such predisposing factors in representative patients. Sequential analyses in a control group with active PTB showed anaemia, thrombocytosis, elevations in plasma fibrinogen, fibrin(ogen) degradation products (FDP), tissue plasminogen activator (t-PA) and inhibitor (PAI-1) with depressed antithrombin III levels. Age, sex and disease matched individuals with venographically proven DVT had higher FDP (15.8 +/- 14.3 v 3.2 +/- 1.7 micrograms/ml:P < 0.01), t-PA (19.4 +/- 14.9 v 11.3 +/- 0.8 ng/ml:P < 0.01), and functional PAI-1 activity (11.6 +/- 6.3 v 4.2 +/- 4.1:P < 0.01) with lower platelet counts (347 +/- 110 v 563 +/- 230 x 10(9)/1:P < 0.01). Fibrinogen levels in all patients rose during the first 2 weeks of therapy and, together with related disturbances, corrected within 12 weeks. In conclusion, elevated plasma fibrinogen with impaired fibrinolysis coupled with a decrease in antithrombin III and reactive thrombocytosis would appear to favour the development of DVT in PTB.

Acute-Phase Reaction↗
PubMed1999

Spontaneous and cytokine-induced thrombocytopenia in myelodysplastic syndromes: serum thrombopoietin levels and bone marrow morphology. Scandinavian MDS Group, Sweden and Norway.

Thrombocytopenia is a substantial clinical problem for patients with myelodysplastic syndromes (MDS). Cytokine treatment for granulocytopenia and anaemia may further reduce the platelet counts. We studied serum thrombopoietin levels (S-TPO) in 52 patients with MDS and 96 healthy controls and related the results to clinical and morphological variables. S-TPO was also assessed after treatment with granulocyte-CSF (G-CSF) and erythropoietin (EPO) in 30 of these patients. S-TPO in MDS was not a normally distributed variable; mean value was 394 pg/ml, SD +/-831 and median value 123 (12-5000 pg/ml). The controls showed lower S-TPO levels than the patients (median 78 pg/ml, P = 0.003) whereas no differences between the MDS subgroups were observed (P = 0.86). Patients with ringed sideroblastic anaemia (RARS) showed the highest platelet counts and higher S-TPO levels than the controls (P = 0.005). No association between platelet counts and S-TPO levels was found in the patients (P = 0.67). TPO levels were generally low in patients with refractory anaemia with an excess of blasts (RAEB), but very high levels were found in five patients. Patients with a high transfusion need had higher S-TPO levels, whereas bone marrow blast counts, cellularity or megakaryocytes showed no correlation with S-TPO. Patients with 5q- showed lower TPO levels than the other patients, indicating that thrombopoietin is not a mediator of thrombocytosis in these cases. Treatment with G-CSF + EPO significantly reduced the platelet counts (P = 0.0002), but this change was not related to significant changes in S-TPO levels or morphology. Patients with RARS and thrombocytosis who normalized their platelet counts showed a concomitant reduction in S-TPO. This may suggest that the increased platelet counts observed in RARS may be caused by increased S-TPO levels. In conclusion, our study shows that platelet, megakaryocyte and thrombopoietin regulation is rather complex in myelodysplastic syndromes and that spontaneous or induced thrombocytopenia are not usually mirrored by increased S-TPO levels.

Aged↗
PubMed1999

Platelet c-mpl expression is dysregulated in patients with essential thrombocythaemia but this is not of diagnostic value.

Essential thrombocythaemia (ET) can be difficult to discriminate from an occult case of reactive thrombocytosis (RT). Since thrombopoietin (TPO) is the primary regulator of thrombopoiesis, we have investigated whether levels of TPO and/or its receptor, c-mpl, are of value in the differential diagnosis of ET. Plasma TPO levels in patients with ET, RT and other myeloproliferative disorders (MPDs) did not differ significantly from normal controls. However, surface c-mpl expression was significantly reduced in platelets from 18 ET patients, 0-65.5% of controls (P < 0.001). Immunoblots on five of these and five additional patients were consistent with absent or reduced c-mpl protein levels. The surface c-mpl expression results were significantly different from those in eight RT patients (21. 3-95.5%, P = 0.0015), but there was considerable overlap between the two groups and a reduced level was not restricted to ET. Furthermore, c-mpl expression in ET patients was not different from eight patients with other MPDs (0-87.6%, P = 0.06), nor could it differentiate between ET patients with monoclonal and polyclonal haemopoiesis. Although a low or absent c-mpl level is suggestive of a primary rather than a secondary thrombocytosis, it is insufficiently discriminatory to be used as a diagnostic marker for ET.

Blood Platelets↗
PubMed2000

Features of essential thrombocythaemia in childhood: a study of five children.

Essential thrombocythaemia (ET) is usually considered a disease of the middle-aged but, with the advent of automated platelet counting, ET is diagnosed with increasing frequency in young adults and, even more rarely, in children. We report five paediatric patients (four girls and one boy, mean age 89 months) diagnosed with ET in agreement with Polycythaemia Vera Study Group criteria. The patients had a persistent thrombocytosis over 900 x 10(9)/l and, at the time of diagnosis, their platelet count ranged between 1,112 and 3,178 x 10(9)/l. A 9-month-old girl had thrombosis of the inferior cava vein, two children had headaches and two others remained asymptomatic throughout the follow-up period. Megakaryocytes in the bone marrow were increased in number. The chromosomal analysis was normal, and bcr rearrangement was always negative. None of the patients had spontaneous BFU-E or altered levels of serum erythropoietin and thrombopoietin. Two patients showed alteration of platelet aggregation, and all had decreased levels of intraplatelet serotonin. In spite of the diagnosis of ET in our patients, we are not sure that the cases reported here are really myeloproliferative disorders. The features could suggest that the cases observed may be affected by an 'idiopathic thrombocytosis' without myeloproliferation. Possible variants of ET are described in young adults, and the heterogeneous nature of ET is also suggested by our paediatric patients. Only careful long-term follow-up of patients such as these will clarify the natural history of these disorders and suggest therapeutic management.

Bone Marrow Cells↗
PubMed2001

Sudden infant death caused by a ruptured coronary aneurysm during acute phase of atypical Kawasaki disease.

This article describe's a case of atypical Kawasaki disease (AKD) with lack of typical clinical signs and rapid fatal course in a 2-month-old infant, who 1 week before hospitalization demonstrated rhinitis, coughing without fever, and later conjunctival hyperemia and allergic exanthema on chest and arms. On admittance, labwork highlighted the following: leukocytosis, thrombocytosis, elevated sedimentation rate, and positive C-reactive protein. General conditions remained mediocre for 7 days until sudden death occurred. The autopsy confirmed death caused by cardiac tamponade caused by a ruptured inflammated aneurysm of the left anterior descending coronary artery. We believe that the currently accepted clinical diagnostics criteria for KD in infants 2 years of age or younger can cause missed in vita diagnosis of AKD. For such, any typical clinical sign of KD whenever associated with thrombocytosis and elevated indices of phlogosis, should led to suspicion of KD and permit cardiovascular examination, and thus early treatment.

Acute Disease↗
PubMed2005

Bone marrow histopathology in myeloproliferative disorders--current diagnostic approach.

Current diagnostic issues in chronic myeloproliferative disorders (MPDs) include the differentiation of essential thrombocythemia (ET) from its mimics: early (prefibrotic) stages of chronic idiopathic myelofibrosis (CIMF) and early polycythemia vera (PV), both of which can be associated with thrombocytosis. Applying a systematic evaluation of bone marrow histopathology, in accordance with the current World Health Organization (WHO) classification system, it is possible to identify cases of true ET as opposed to false ET, usually early-stage CIMF accompanied by an excess of platelets. This distinction is important because the frequency of complications such as progression to overt myelofibrosis, blastic crisis, and overall prognosis are significantly different in the two conditions. The diagnostic criteria of the Polycythemia Vera Study Group (PVSG) do not adequately define the initial stages of PV, nor do they distinguish PV with thrombocytosis from ET. Differentiation of the two is possible by bone marrow histopathology, which also is highly predictive (96%) in distinguishing PV from secondary polycythemia. In conclusion, bone marrow biopsy is an important diagnostic tool for distinguishing specific subtypes of MPD and should be a mandatory step for entry evaluation and follow-up of patients enrolled in prospective studies and/or clinical trials.

Bone Marrow↗
PubMed2005

Polycythemia vera: scientific advances and current practice.

Polycythemia vera (PV) is a clonal disorder of unknown etiology involving a multipotent hematopoietic progenitor cell that is characterized by the accumulation of phenotypically normal red blood cells, white blood cells, and platelets in the absence of a definable cause; extramedullary hematopoiesis, marrow fibrosis, and, in a few patients, transformation to acute leukemia can also occur. First described in 1892, the cause of the disease remains unknown and no potentially curative therapy other than bone marrow transplantation is currently available. It is commonly held that PV is a rare disorder, when in fact with a minimum incidence of 2.6 per 100,000 it is more common than chronic myelogenous leukemia (CML) and is particularly prevalent in persons of Ashkenazi Jewish ancestry. However, the incidence of PV is not as high as that of erythrocytosis from other causes collectively, which poses a problem in differential diagnosis when PV presents as isolated erythrocytosis. Characteristic features of PV are erythropoietin (Epo)-independent in vitro erythroid colony formation, as well as hypersensitivity to many other hematopoietic growth factors. Recently, a remarkable association between PV and a somatic point mutation of the JAK2 tyrosine kinase (JAK2 V617F) was described. Functional assays have revealed that JAK2 V617F is capable of inducing constitutive STAT5-mediated signaling in vitro, as well as erythrocytosis in vivo in mice. These data suggest that the JAK2 V617F mutation participates in the pathogenesis of PV. In current clinical practice, two different clinical approaches have been used to diagnose PV. One approach requires establishing the presence of absolute erythrocytosis by directly determining the red cell mass (RCM). A second approach utilizes a RCM-independent diagnostic algorithm based on the serum Epo level and bone marrow histology. Screening for JAK2 V617F can now be added to both diagnostic algorithms. However, it is very clear that some patients with classical PV lack the JAK2 V617F mutation, while some patients with other chronic myeloproliferative disorders such as idiopathic myelofibrosis (IMF) and essential thrombocytosis (ET) also express the JAK2 V617F mutation. Therefore, by necessity, any discussion of PV must take into consideration these companion myeloproliferative disorders, and since erythrocytosis is the single clinical feature that sets PV apart from IMF and ET, it is clear that the presence of the JAK2 V617F mutation cannot by itself establish a diagnosis of PV. Phlebotomy remains the mainstay of therapy for PV. In addition, both aspirin and cytoreductive therapy have been employed to control thrombocytosis and in the case of the latter, leukocytosis and extramedullary hematopoiesis as well. Despite recent progress in the field, several important issues remain controversial. In this review, we will present the areas of agreement, but also point out where the authors' personal viewpoints differ.

Erythroid Precursor Cells↗
PubMed1987

Hematological changes associated with marathon running.

Coulter profiles with differential white cell counts, serum ferritin, and haptoglobin levels were determined in venous blood samples obtained from 90 males (M) and 25 females (F) immediately before and after completion of a competitive marathon (42.2 km) race. In an additional 20 male runners, the same measurements were performed serially during the 24 h following their completion of the race. In the pre-race samples from 90 M and 25 F, hypoferritinemia was present in 4/22 M and 1 F found to be mildly anemic. Neutropenia was detected in 4 M and 3 F and mild thrombocytopenia in 2 M. Haptoglobin levels were normal in all the female runners but reduced (less than 0.3 g/l) in 6 M. All post-race samples (88 M and 25 F) were characterized by a reactive neutrophilia and thrombocytosis including those with pre-race neutropenia or thrombocytopenia. An unexpected and incompletely explained sex difference in packed cell volume (PCV) response was observed. In males, the mean PCV increased from 0.425 +/- 0.021 to 0.444 +/- 0.028 (P less than 0.0001) whereas in females it decreased from 0.437 +/- 0.029 to 0.423 +/- 0.036 (P less than 0.05). In the post-race samples, anhaptoglobinemia was found in 13/88 M and 4/25 F. In the 20 male runners studied serially for 24 h after the race, the major changes involved a progressive increase in mean plasma volume (17.4% +/- 12.2% at 24 h) compared with the pre-race value, a progressive and significant increase in MCH and MCHC probably indicating a loss in red cell water and the gradual reversion of the reactive neutrophilia and thrombocytosis to basal levels.

Adult↗
PubMedDate not supplied

[Increased thrombocyte count in newborn infants of drug-dependent mothers].

In a retrospective study we analysed clinical findings and hematological data of 16 neonates born from mothers using methadone and other drugs during pregnancy. Most infants presented with symptoms of drug withdrawal and needed medication. Hemoglobin concentration and leucocyte counts were within normal limits, whereas all infants showed thrombocytosis after the first week of life with thrombocyte counts (median) of 566,750 (week 2), 628,500 (week 3), 629,500 (week 4), 617,000 (week 5) and 639,150/mm3 (week 6). No thrombocytosis was found in 18 normal control infants which showed significantly lower platelet counts during the first days (p < 0.05) and by the second week of life (p < 0.001). The cause of this phenomenon is not known. Sudden infant death syndrome occurred in 1 infant. There are speculations that the high incidence of SIDS in this group of patients could be explained by thromboembolic complications in some of the cases.

Birth Weight↗
PubMed1982

Deficiency of platelet lipoxygenase activity in myeloproliferative disorders.

The myeloproliferative disorders are characterized by frequent bleeding and thrombotic complications, which have been attributed to abnormal platelet function. In 24 of 60 patients studied, reduced activity of the platelet lipoxygenase pathway for oxygenation of arachidonic acid was revealed by a new direct assay. This assay measured arachidonic acid-induced oxygen consumption in platelets preincubated with aspirin to block cyclooxygenase activity. Patients with secondary polycythemia or thrombocytosis had normal lipoxygenase activity . In the cells of seven of eight patients with lipoxygenase deficiency arachidonic acid induced increased synthesis of thromboxane, the major cyclooxygenase product. Nevertheless, patients with deficient lipoxygenase activity tended to have episodes of hemorrhage rather than thrombosis. Bleeding complications occurred in 67 per cent of patients with lipoxygenase deficiency, but in only 19 per cent of those with normal lipoxygenase activity (P less than 0.001). In contrast, 13 per cent of lipoxygenase-deficient patients, but 31 per cent of patients with other myeloproliferative disorders, had thromboembolic complications. Measurement of platelet lipoxygenase activity may be of diagnostic value in distinguishing myeloproliferative disorders from secondary thrombocytosis or polycythemia. Lipoxygenase deficiency may prove to be a useful natural model for investigating the role of lipoxygenase products in hemostasis.

Blood Platelets↗
PubMed2004

Factors affecting clinical and therapeutic outcomes of patients with juvenile rheumatoid arthritis.

OBJECTIVE: To investigate clinical features, medications, and therapeutic responses of juvenile rheumatoid arthritis (JRA) among Taiwanese children. METHODS: A retrospective chart review was conducted among all children newly diagnosed with JRA at the National Taiwan University Hospital between 1996 and 2001. RESULTS: Forty boys and 30 girls were enrolled in the study. The mean follow-up was 45 months. Oligoarticular onset was the most common type. A bimodal distribution of age at onset was observed, with peaks at 4 and 10 years. All patients received non-steroidal anti-inflammatory drugs (NSAIDs); 27 (39%) received corticosteroids, and 44 (63%) had second-line drugs during the first course of treatment. Forty-three patients (69%) achieved clinical remission after a mean of 14.8 months of medication, and 19 (31%) were drug-dependent. The major factors related to the failure of first remission were human leukocyte antigen B27 (HLA-B27), high C-reactive protein (CRP) level, and thrombocytosis at diagnosis. CONCLUSION: There are different phenotypic features among Taiwanese children with JRA. Factors related to the failure of first remission were HLA-B27, high CRP level, and thrombocytosis at diagnosis.

Adrenal Cortex Hormones↗