Aetiology and clinical significance of thrombocytosis: analysis of 732 patients with an elevated platelet count

Incidence and etiology of thrombocytosis in an adult Turkish population

The aim of the study was to determine the incidence and etiology of thrombocytosis in an adult Turkish population. The medical records of 2000 patients were reviewed retrospectively to determine (i) the etiology of elevated platelet counts, (ii) additional laboratory parameters (i.e., complete blood counts), and (iii) the presence of thromboembolic complications. Within 5 years, 174 678 platelet counts had been performed for 124,340 patients. Of the 124,340 patients, 2000 (1.6%; mean age, 55.2 +/- 17.4 years; range 16-94 years; male-to-female ratio, 3.6:1 [1570:430]) had one or more platelet counts of 500 x 10(3)/mm3 or higher during the study period. Secondary thrombocytosis was the most frequent cause of an elevated platelet count and occurred in 1934 cases (96.7%). Infection was the most common cause of secondary thrombocytosis, occurring in 1001 patients (50.1%). Compared with secondary thrombocytosis, primary thrombocytosis was significantly associated with a higher rate of thromboembolic complications. It is concluded that a high platelet count may have both diagnostic and therapeutic implications. Secondary thrombocytosis is a common finding and mostly secondary to infection. Primary thrombocytosis has a higher risk for thromboembolic events than does secondary thrombocytosis.

Thrombosis of the splenoportal axis after splenectomy

BACKGROUND AND AIMS

Thrombosis of the portal system is a potentially life-threatening complication after splenectomy. The reported incidence is low (approximately or = 1%), however may be underestimated due to difficult in making the diagnosis. The factors associated with its development and the clinical outcome are poorly characterized. The aim of this study was to assess the incidence, risk factors, treatment, and outcome in series of consecutive cases.

MATERIALS AND METHODS

All patients who had undergone a splenectomy (both open and laparoscopic) between January 1997 and December 2004 at the Department of Surgery of University of Milan Bicocca were retrospectively reviewed. Twelve cases of thrombosis (7.6%) among 158 splenectomies were identified. No significant differences were noted in age, gender, and surgical approach between patients who developed thrombosis and those who did not. Indication for splenectomy in patients with thrombosis were myeloproliferative disorders (n=5), hemolytic disease (n=4), and lymphoproliferative disorder (n=3). All patients had splenomegaly (mean 1.380 kg, range 0.400-3.120 kg).

RESULTS

Among patients with myeloproliferative disorders, five (33%) developed the complication, compared with 4 of 35 (11.5%) with hemolytic disease. Patients with both splenic weight >2.500 kg and myeloproliferative disorders had 80% incidence of portal thrombosis. Preoperative prophylactic anticoagulant therapy with low molecular weight heparin was administered in each case. All these patients had fever, abdominal pain, or leukocytosis. All diagnoses were made by contrast-enhanced computed tomography (CT) scan and ecocolordoppler ultrasonography, and anticoagulation therapy was initiated immediately. Treatment within 15 days after splenectomy was successful in all patients, while delayed treatment was ineffective.

CONCLUSIONS

Portal thrombosis should be suspected in patients with fever or abdominal pain after splenectomy. Patients with myeloproliferative disorders and hemolytic diseases are at higher risk, as well as patients with marked splenomegaly. A high index of suspicion, early diagnosis, and prompt anticoagulation therapy are the keys to a successful outcome.

A critical reappraisal of the WHO classification of the chronic myeloproliferative disorders

Following the introduction of the WHO classification of chronic myeloproliferative disorders (MPDs), after approximately 5 years, a critical reappraisal appears to be warranted. Retrospective clinico-pathological evaluations conducted in the meantime, as well as the detection of new biomarkers, may aid in testing the validity of these new criteria. Based on a large series of patients with chronic myeloid leukemia (CML), an analysis of bone marrow (BM) features and risk classifications revealed that the fiber content exerted a most important and independent impact on prognosis. This finding was also supported in a prospective randomized study and therefore myelofibrosis should be included in any staging system in CML related to survival. Moreover, it is important to emphasize the dynamics of the disease process in MPDs, especially in polycythemia vera (PV) and chronic idiopathic myelofibrosis (CIMF). Latent-stage PV is difficult to recognize when adhering to the proposed limits for hemoglobin (or red cell mass) without regarding the erythropoietin (EPO) level, endogenous erythroid colonies (EECs) or BM histopathology. Initial PV may firstly present with complications and, when accompanied by a high platelet count, mimics essential thrombocythemia (ET). Consequently, BM morphology and EPO level should be entered as major diagnostic criteria for PV. To document more accurately the progress of disease, a simplified scoring system concerning myelofibrosis has to be included in the histological description of CIMF. The diagnostic guidelines of BM features in ET should be improved because, usually, there is neither a significant proliferation nor left-shifting of the granulo- and erythropoiesis detectable and no relevant increase in reticulin. A comparison of clinical data and BM morphology reveals that biomarkers (EPO, EECs, PRV-1, JAK2) show an overlapping pattern of positivity between the different subtypes of MPDs.

Platelet counts are persistently increased following simultaneous pancreas and kidney transplantation

BACKGROUND

Increased platelet counts has been reported to be a sequela of pancreas transplantation and even incriminated in the increased rate of thrombosis of pancreas grafts. The aim of the study was to measure the platelet counts after simultaneous kidney-pancreas transplantations compared to kidney transplants alone in diabetic patients.

METHODS

This retrospective case-control study included 57 patients who received simultaneous pancreas and kidney transplants (SPK), from 1985 to 2000 and had functioning grafts for more than 1 month. The control patients were 38 type I diabetic recipients of kidney transplants alone (KTA), matched for sex, era, and immunosuppression. The platelet counts, white cell counts, and hemoglobin were analyzed on the preoperative day, weeks 1 to 6, 3 months, 6 months and 1 year.

RESULTS

The mean age of the SPK group was significantly lower than that of the KTA group (39.8+/-8.3 versus 48.2+/-11.7, P<.01). Significantly higher platelet counts were demonstrated during weeks 2 to 6, which persisted at 3 months and at 1 year among the SPK compared to the KTA group. Although significantly higher white cell counts and lower hemoglobin levels were seen among the SPK versus KTA group during weeks 3 to 6, it did not persist after 3 months.

CONCLUSION

The mean platelet counts of patients with simultaneous pancreas and kidney transplantation was significantly higher than that of diabetic patients with kidney transplants alone. This thrombocytosis persisted up to the first year and cannot be explained by an increased amount of blood loss or higher infectious complications in the SPK group. Routine antiplatelet prophylaxis is recommended in this group of patients.

Molecular basis of the diagnosis and treatment of polycythemia vera and essential thrombocythemia

Recent insights into the molecular mechanisms of polycythemia vera (PV) and essential thrombocythemia (ET) are challenging the traditional diagnostic classification of these myeloproliferative disorders (MPDs). Clonality analysis using X-chromosome inactivation patterns has revealed apparent heterogeneity among the MPDs. The recently discovered single somatic activating point mutation in the JAK2 gene (JAK2-V617F) is found in the great majority of patients with PV, but also in many patients with phenotypically classified ET and other MPDs. In contrast to the acquired MPDs, mutations of the erythropoietin receptor and thrombopoietin receptor have been identified in familial forms of nonclonal erythrocytosis and thrombocytosis, respectively. The mechanisms of major clinical complications of PV and ET remain poorly understood. Quantitative or qualitative abnormalities of red cells and platelets do not provide clear explanations for the thrombotic and bleeding tendency in these MPDs, suggesting the need for entirely new lines of research in this area. Recently reported randomized clinical trials have demonstrated the efficacy and safety of low-dose aspirin in PV, and an excess rate of arterial thrombosis, major bleeding, and myelofibrotic transformation, but decreased venous thrombosis, in patients with ET treated with anagrelide plus aspirin compared to hydroxyurea plus aspirin.

Reactive thrombocytosis: an early manifestation of Takayasu arteritis

A woman with Takayasu arteritis is reported who presented with constitutional symptoms and persistent thrombocytosis documented since 3 years before the diagnosis. Disease-specific symptoms such as arm claudication, transient loss of vision, and self-remitting eye ptosis present at the time were apparently missed, because she is a non-English-speaking Hispanic woman whose history was obtained through an interpreter. Extensive workup done at the time failed to reach a definite etiology. A computed tomography scan of the chest done because of midthoracic back pain and an elevated erythrocyte sedimentation rate showed circumferential wall thickening and mild surrounding edema throughout the thoracic and abdominal aorta and both carotid arteries consistent with Takayasu arteritis. Prednisone at a dosage of 1 mg/kg twice a day decreased the platelet count within 45 days of its initiation. Takayasu arteritis should be considered in the differential diagnosis of unexplained thrombocytosis, particularly in young women.

The molecular mechanisms that control thrombopoiesis

Our understanding of thrombopoiesis--the formation of blood platelets--has improved greatly in the last decade, with the cloning and characterization of thrombopoietin, the primary regulator of this process. Thrombopoietin affects nearly all aspects of platelet production, from self-renewal and expansion of HSCs, through stimulation of the proliferation of megakaryocyte progenitor cells, to support of the maturation of these cells into platelet-producing cells. The molecular and cellular mechanisms through which thrombopoietin affects platelet production provide new insights into the interplay between intrinsic and extrinsic influences on hematopoiesis and highlight new opportunities to translate basic biology into clinical advances.

Thrombocytosis accompanying urinary tract infection suggests obstruction or abscess

OBJECTIVE

Reactive thrombocytosis can be found in patients with different types of infections, including upper urinary tract infection (UTI). In this study, we determined whether thrombocytosis in patients with upper UTI is a random phenomenon or is related to complications associated with the UTI.

METHODS

We reviewed the charts of patients admitted to the urology department with a diagnosis of upper UTI and thrombocytosis (platelet count >500 x 10(9)/L) in the years 1991 to 2003 (study group). Patients admitted to the urology department in the year 2003 with a diagnosis of upper UTI without thrombocytosis served as the control group.

RESULTS

The study group consisted of 83 patients admitted to the urology department with a diagnosis of upper UTI and thrombocytosis (mean platelet count, 593 x 10(9)/L; SD, 88; range, 501-949). The control group consisted of 99 patients. An obstructed kidney was found in 54 patients (65%) of the study group and in 18 patients (18%) of the control group (P < .00001). Perinephric abscess was found in 7 patients (8%) in the study group compared with none in the control group (P < .003). The positive predictive value of thrombocytosis for kidney obstruction or abscess in patients with upper UTI was 71%. Nephrectomy of a nonfunctioning infected kidney was required in 6 patients of the study group (7%) and 2 of the control group (P = .14). In 26 patients (31%) of the study group, the finding of thrombocytosis preceded the diagnosis of the complication (by a median period of 3 days). In these patients, thrombocytosis was essentially an early marker for the complication.

CONCLUSIONS

Thrombocytosis in a patient with upper UTI is not a random phenomenon. It is a marker of kidney obstruction or perinephric abscess. The finding of thrombocytosis in a patient with upper UTI should alert the attending physician to actively search for these complications. Cross-sectional imaging study (abdominal ultrasonography or computed tomography) should be performed.

Thrombocytosis During Antifungal Therapy of Candidemia

BACKGROUND

Secondary, “reactive,” thrombocytosis has been attributed to bacterial infection and treatment with multiple pharmaceuticals and may be associated with an increase in the incidence of gastrointestinal tract bleeding and thrombotic events (eg, stroke).

OBJECTIVE

To characterize the dynamics of thrombocytosis in patients with candidemia receiving antifungal therapy.

METHODS

We initiated a retrospective observational description of patients with candidemia who were treated with antifungal agents. A total of 108 patients diagnosed with candidemia between August 1995 and September 2003 at our teaching hospital were enrolled. Three groups (candidemia with antifungal therapy, candidemia without antifungal therapy, antifungal therapy without candidemia) of patients >18 years of age were evaluated for the resence of thrombocytosis. Platelet administration, pharmacologic or pathologic contributors to thrombocytosis, and other pertinent details related to an elevation of platelet counts were scrutinized.

RESULTS

Reactive thrombocytosis was observed in approximately 10% of treated patients with candidemia. Within the subgroup developing reactive thrombocytosis, life-threatening thrombotic complications were uncommon. Mean baseline platelet counts were 393 × 103/mm3, with a mean peak (695 × 103/mm3) occurring an average of 13 days after initiation of therapy. All patients had resolution within 7 days after therapy. The maximum peak (1056 × 103/mm3) was observed in a patient after 14 days of antifungal therapy. The onset of thrombocytosis in this patient was 4 days and lasted 4 days after therapy.

CONCLUSIONS

Reactive thrombocytosis occurs during treatment of candidemia. The causative agent (drug vs disease), the risk associated with this reaction, and evaluation of treatment need to be elucidated by a larger epidemiologic study or controlled, prospective clinical trial.

Engagement of integrin alpha4beta1 enhances thrombopoietin-induced megakaryopoiesis

OBJECTIVE

Studies in numerous adherent cell systems have indicated that engagement of integrins is required for cell survival and proliferation. Although not classically thought of as an adherent cell type, megakaryocytes in the marrow develop in juxtaposition to endothelial cells which display a number of integrin counter-receptors. Moreover, a number of other hematopoietic cell types, including stem cells and erythroid progenitors, have been shown to engage and be affected by integrin ligands.

METHODS

The role of beta1 integrins in thrombopoietin-mediated megakaryopoiesis was studied using both gain-of-function and loss-of-function strategies.

RESULTS

We found that pan-blockade of integrins with a relatively nonspecific disintegrin blocked TPO-induced MK growth, but that an alpha5beta1 disintegrin, and a function-blocking monoclonal antibody, failed to affect megakaryopoiesis in vitro. In contrast, a neutralizing alpha4beta1 monoclonal antibody blocked TPO-induced MK growth, and an integrin alpha4beta1 ligand, the H296 fragment of fibronectin, enhanced MK growth at all concentrations of TPO.

CONCLUSIONS

These findings have important implications for thrombopoiesis in general, and potentially for the enhanced platelet production found in states of systemic inflammation and following the use of therapeutic strategies designed to block alpha4beta1 integrin engagement in states of chronic inflammation and autoimmunity.

Thrombocytopenia in Cardiovascular Patients

Thrombocytopenia is a common problem in cardiovascular patients, but the etiology and management of this condition may be different than those in other populations. Around the time that percutaneous coronary interventions are performed, the drugs most commonly associated with thrombocytopenia are the glycoprotein (GP) IIb/IIIa receptor inhibitors and heparin. Thienopyridines only rarely cause thrombocytopenia. Patients with non-ST-elevation acute coronary syndromes may be exposed to prolonged heparin infusions, GPIIb/IIIa inhibitors, and thienopyridines. After open-heart surgery, as opposed to other surgical procedures, the platelet count falls, primarily due to platelet damage and destruction in the bypass circuit and hemodilution. Heparin is the most common drug to be implicated in thrombocytopenia in ICU patients. Determining the etiology for the low platelet count is important for the implementation of appropriate management. The use of a direct thrombin inhibitor in treatment should be considered early if a diagnosis of heparin-induced thrombocytopenia is possible.

Thrombocytosis after trauma: incidence, aetiology, and clinical significance

BACKGROUND

Our aim was to assess the occurrence, aetiology, and clinical significance of a platelet count greater than 600 x 10(3)/mm(3) in trauma patients.

METHODS

All trauma patients admitted to the intensive care unit (ICU) during a 13-month period were prospectively studied. Platelet counts were performed daily. We recorded the patient's age, sex, nature of trauma, severity of illness scores, episodes of infections in the ICU, acute lung injury, bleeding, and thromboembolic events. Patients with thrombocytosis were also followed during their hospital stay and 1 month after hospital discharge.

RESULTS

A total of 176 patients were included. Thrombocytosis developed in 36 patients (20.4%) at a mean (sd) time of 14.0 (4.0) days and the platelet count normalized 35.0 (13.0) days after admission to the ICU. All patients with thrombocytosis had one or more possible predisposing conditions before the occurrence of thrombocytosis: nosocomial infection occurred in 30 patients (83%), acute lung injury in 17 (47%), bleeding in 27 (75%), and administration of cathecholamines in 24 (67%). Three venous thromboembolic complications occurred in the ICU (1.7%) and one during follow-up. Only one patient presented thrombocytosis at the time of diagnosis. Despite the fact that patients with thrombocytosis had a greater severity of illness, the ICU mortality was comparable among patients with and without thrombocytosis (8 vs 14%, P=0.34).

CONCLUSIONS

Reactive thrombocytosis is a common finding after severe trauma and was found to be associated with a better survival than predicted by severity of illness score. Unless additional risk factors are present, reactive thrombocytosis is not associated with an increased risk of thromboembolic events.

Significance of thrombocytosis for determining prognosis in patients with localized renal cell carcinoma

OBJECTIVES

To evaluate the significance of thrombocytosis for determining survival in patients with localized renal cell carcinoma (RCC) who underwent radical nephrectomy with curative intent.

METHODS

The study population comprised 151 patients who underwent radical nephrectomy with a diagnosis of localized RCC. The inclusion criteria were at least one preoperative platelet count and a tissue diagnosis of RCC. Thrombocytosis was defined as a platelet count greater than 400,000/mm3. The charts of these patients were retrospectively reviewed and the relationship between the preoperative platelet counts and survival was evaluated according to the histologic variants.

RESULTS

The mean follow-up was 37.1 +/- 24.1 months (median 34, range 3 to 91). Of these 151 patients, 21 had a preoperative platelet count greater than 400,000/mm3. The thrombocytosis rate was significantly greater in those with advanced T stage (P = 0.045). Lymph node positivity also correlated with thrombocytosis (P = 0.028). However, no statistically significant correlation was found between grade and histologic subtypes and thrombocytosis (P = 0.053 and P = 0.354, respectively). Ten (47.6%) of 21 patients with thrombocytosis and 21 (16.2%) of the remaining 130 patients died of disease progression (P = 0.002). The Kaplan-Meier cause-specific survival curves showed that patients who had thrombocytosis had a mean survival of 45.2 months compared with 76.6 months in patients without thrombocytosis (P = 0.0002).

CONCLUSIONS

Preoperative thrombocytosis is a significant predictor for determining prognosis in patients with localized RCC. Thrombocytosis was found more frequently in patients with advanced stage RCC, and patients with preoperative thrombocytosis had a worse survival compared with those with normal platelet counts.

Thromboembolic complications after splenectomy for hematologic diseases

Thromboembolic complications following splenectomy for hematologic diseases occur in up to 10% of patients and may range from portal vein thrombosis (PVT) to pulmonary embolism (PE) and deep vein thrombosis (DVT). Up to now there exist no recommendations for the duration and intensity of prophylactic anticoagulation, which usually follows local institutional protocols. We report on three consecutive patients with severe portal vein thrombosis and/or pulmonary embolism--one with fatal outcome--7 to 35 days after splenectomy for autoimmune hemolytic anemia, immunothrombocytopenia, and indolent lymphoma, respectively. Incidence and pathophysiology of thromboembolic events (TE) in this patient group as well as prophylactic anticoagulation will be discussed, including a review of the current literature on this topic.

Essential thrombocythemia

Essential thrombocythemia is a distinct clinical entity within the spectrum of myeloproliferative disorders. There is as yet no pathognomonic diagnostic test, and patients who currently fall into the category of essential thrombocythemia are likely to be heterogeneous. This article discusses diagnostic criteria, clinical features, prognosis, and management.

Influence of talc dose on extrapleural talc dissemination after talc pleurodesis

This study was designed to ascertain, in a rabbit model, extrapleural talc deposition and the related inflammatory response after talc slurry pleurodesis with two clinical doses, 200 and 50 mg/kg. Histopathologic evaluations revealed that whereas numerous rabbits receiving a high dose had talc in the ipsilateral (70%) and contralateral (55%) lung, mediastinum (90%), pericardium (30%), and liver (25%), a small number of animals treated with a low dose showed talc in the ipsilateral lung (10%) and mediastinum (20%) and none in the contralateral lung, pericardium, or liver. Hematologic and immunocytochemical analyses showed that a systemic inflammatory response develops shortly after pleurodesis with a high talc dose involving massive accumulation of neutrophils and macrophages in lung tissue. Zymography also revealed that the pulmonary expression of matrix metalloproteinases 2 and 9 was up-regulated in both lungs in a dose-dependent manner soon after talc instillation. Furthermore, microscopic examination of lung specimens revealed that the higher the dose of talc, the greater the development of both fibrotic visceral pleural thickening and foreign-body granulomas. These findings show pleurodesis with a high talc dose to be associated with an increased risk of extrapleural talc deposition, which may originate undesirable acute and chronic inflammatory responses.

Screening toxicity study in young carp (Cyprinus carpio L.) on feed amended with fumonisin B1

Fumonisin B1 (FB1) is one of several mycotoxins produced by Fusarium moniliforme, a major fungal pathogen of corn and widely spread throughout the world. FB1 produces a wide range of biological effects, some of which are specific for particular organs or species and some are common to all investigated animals. In this study we have evaluated subchronic toxicosis features in young carp (Cyprinus carpio L.) exposed to 0.5 and 5.0 mg FB1 kg(-1) body weight for 42 days through nutritionally balanced diet. During the trial we observed loss of body weight in both treated groups, together with higher incidence of infective bacterial dermatological lesions erythrodermatitis cyprini (Aeromonas salmonicida subsp. nova) in the group treated with the higher FB1 dose. Several hematological parameters (erythrocyte count, platelet count) and serum chemical concentrations (creatinin, total bilirubin) and activities (aspartate aminotransferase, AST and alanine aminotransferase, ALT) were greater in the fumonisin treated groups than in the control group. Our results indicate that long-term dietary exposure to 0.5 and 5.0 mg FB1 kg(-1) body weight is not lethal to young carp, but can produce adverse physiological effects. These findings also suggest that primary target organs of FB1 in the carp are kidney and liver, as it has already been observed in other animal species tested. Specifically changed red blood cell- parameters reveal that FB1 probably causes erythrocyte membrane defect or interferes with carp's respiratory process.

The hematologic system as a marker of organ dysfunction in sepsis

Sepsis with acute organ dysfunction (severe sepsis) results from a systemic proinflammatory and procoagulant response to infection. Organ dysfunction in the patient with sepsis is associated with increased mortality. Although most organs have discrete anatomical boundaries and carry out unified functions, the hematologic system is poorly circumscribed and serves several unrelated functions. This review addresses the hematologic changes associated with sepsis and provides a framework for prompt diagnosis and rational drug therapy. Data sources used include published research and review articles in the English language related to hematologic alterations in animal models of sepsis and in critically ill patients. Hematologic changes are present in virtually every patient with severe sepsis. Leukocytosis, anemia, thrombocytopenia, and activation of the coagulation cascade are the most common abnormalities. Despite theoretical advantages of using granulocyte colony-stimulating factor to enhance leukocyte function and/or circulating numbers, large clinical trials with these growth factors are lacking. Recent studies support a reduction in the red blood cell transfusion threshold and the use of erythropoietin treatment to reduce transfusion requirements. Treatment of thrombocytopenia depends on the cause and clinical context but may include platelet transfusions and discontinuation of heparin or other inciting drugs. The use of activated protein C may provide a survival benefit in subsets of patients with severe sepsis. The hematologic system should not be overlooked when assessing a patient with severe sepsis. A thorough clinical evaluation and panel of laboratory tests that relate to this organ system should be as much a part of the work-up as taking the patient's blood pressure, monitoring renal function, or measuring liver enzymes.

Reactive thrombocytosis without endothelial damage does not affect the microvascular anastomotic patency

There is still controversy about the correlation of thrombocytosis and thrombosis complication. Using a rodent splenectomy-induced thrombocytosis model and a thrombogenic endothelial damage model (inverted suture resulting in an intraluminal thrombogenic adventitia of divided femoral artery), the authors investigated whether reactive thrombocytosis with or without endothelial damage contributes to the patency of microvascular anastomosis. Four experimental groups were evaluated in this study: 1) sham operation without thrombogenic anastomosis after femoral artery division; 2) sham operation with thrombogenic anastomosis; 3) thrombocytosis alone without thrombogenic anastomosis; 4) thrombocytosis with thrombogenic anastomosis (each subgroup n = 10, total N = 40). Vascular patency was assessed after immediate operation and on the seventh day postoperatively. Platelet counts and platelet activation (CD62P) were studied in correlation to microvascular patency. In rats without thrombogenic anastomosis groups, there were no significant differences in CD62P expression on platelets (p = 0.09), the patency rates (p = 0.561), or perfusion units (p = 0.746) before and after arterial reanastomosis between rats with and without thrombocytosis, respectively. However, the thrombogenic anastomosis of femoral artery in thrombocytosis and control groups showed significantly increased CD62P expression (p < 0.05), decreased the perfusion unit (p < 0.05), and patency rate (p < 0.001), compared with rats without thrombogenic anastomosis of femoral artery in both groups. In summary, this study demonstrates that microvascular anastomosis can be performed safely with reactive thrombocytosis alone without thrombogenic anastomosis. Meticulous microvascular anastomosis without triggering platelet activation is the most important factor to prevent thrombosed vessels in microsurgical anastomosis.

The molecular and cellular biology of thrombopoietin: the primary regulator of platelet production

The term thrombopoietin (TPO) was first coined in 1958 and used to describe the humoral substance responsible for causing the platelet count to rise in response to thrombocytopenic stimuli. Despite much progress during the 1980s in the purification and characterization of the humoral regulators of lymphocyte, erythrocyte, monocyte and granulocyte production, the successful search to purify and molecularly clone thrombopoietin did not begin until the oncogene v-mpl was discovered in 1990. Since that time the proto-oncogene c-mpl was identified and, based on homology arguments, believed to encode a hematopoietic cytokine receptor, a hypothesis later proven when the cytoplasmic domain was linked to the ligand binding domain of the IL-4 receptor and shown to support the IL-4 induced growth of hematopoietic cells (Skoda et al., 1993). Finally, two different strategies using c-mpl lead to the identification of a novel ligand for the receptor in 1994 (de Sauvage et al., 1994; Lok et al., 1994; Bartley et al., 1994), a protein that displays all the biologic properties of TPO. This review attempts to distill what has been learned of the molecular and cellular biology of TPO and its receptor during the past several years, and links this information to several new insights into human disease and its treatment.

White blood cell count in generalized aggressive periodontitis after non-surgical therapy

BACKGROUND

Periodontal bacteria are known to invade the systemic circulation. Chronic low-level bacteremia and a systemic inflammatory response have been suggested as a pathogenetic link between periodontal disease and atherosclerosis. The purpose of this study was to examine the systemic effect of a non-surgical therapy on white blood cell count (WBC count) and differential blood count in smoking and non-smoking generalized aggressive periodontitis (GAP) patients.

METHODS

27 adult periodontitis patients (13 smokers and 14 non-smokers) with previously untreated GAP were subjected to 3 sessions of oral hygiene procedure. Afterwards, the patients were treated by scaling and root planing under local anaesthesia. Periodontal examinations were performed after supragingival pretreatment and three months after subgingival therapy. Pocket probing depth (PPD) and relative attachment level (RAL) were measured with Florida probe and disc probe. Accompanying clinical evaluation venous blood samples were taken to analyse the WBC counts and differential blood counts. For statistical analysis non-parametric tests were utilized.

RESULTS

No clinical or demographic differences were found between smokers (n=13) and non-smokers (n=14). PPD, bleeding on probing (BoP) and suppuration improved significantly after therapy both in smokers and non-smokers. Following periodontal treatment WBC counts, neutrophil and platelet counts decreased significantly in non-smokers (p< or =0.004), while in smokers only platelet counts were significantly reduced (p=0.006). Non-smokers showed a significantly higher reduction of WBC counts (p=0.005) and neutrophils (p=0.001) compared to smokers.

CONCLUSION

The results indicate that a therapeutical intervention may have a systemic effect on the blood count in GAP patients. This effect seems to differ between smokers and non-smokers.

Interleukin-6 stimulates thrombopoiesis through thrombopoietin: role in inflammatory thrombocytosis

Baseline platelet production is dependent on thrombopoietin (TPO). TPO is constitutively produced and primarily regulated by receptor-mediated uptake by platelets. Inflammatory thrombocytosis is thought to be related to increased interleukin-6 (IL-6) levels. To address whether IL-6 might act through TPO to increase platelet counts, TPO was neutralized in vivo in C57BL/10 mice treated with IL-6, and hepatic TPO mRNA expression and TPO plasma levels were studied. Transcriptional regulation of TPO mRNA was studied in the hepatoblastoma cell line HepG2. Furthermore, TPO plasma levels were determined in IL-6-treated cancer patients. It is shown that IL-6-induced thrombocytosis in C57BL/10 mice is accompanied by enhanced hepatic TPO mRNA expression and elevated TPO plasma levels. Administration of IL-6 to cancer patients results in a corresponding increase in TPO plasma levels. IL-6 enhances TPO mRNA transcription in HepG2 cells. IL-6-induced thrombocytosis can be abrogated by neutralization of TPO, suggesting that IL-6 induces thrombocytosis through TPO. A novel pathway of TPO regulation by the inflammatory mediator IL-6 is proposed, indicating that the number of platelets by themselves might not be the sole determinant of circulating TPO levels and thus of thrombopoiesis. This regulatory pathway might be of relevance for the understanding of reactive thrombocytosis.

Current opinion in essential thrombocythemia: pathogenesis, diagnosis, and management

A working diagnosis of essential thrombocythemia (ET) is made in the presence of nonreactive thrombocytosis and after the exclusion of another chronic myeloid disorder that may mimic ET in its presentation. Clinically, ET is characterized by vasomotor symptoms, thrombohemorrhagic complications, recurrent fetal loss, and transformation of the disease into either myelofibrosis with myeloid metaplasia or acute myeloid leukemia. Median survival in the majority of patients is close to that of an age-adjusted normal population, and current therapy has not been shown to either retard or hasten leukemic transformation, which is reported to occur in 1% to 20% of patients. The use of hydroxyurea in high-risk patients with ET has reduced the incidence of thrombosis, and recent studies have suggested the value of keeping the platelet count below 400 x 10(9)/L in such cases. The incidence of thrombosis in low-risk patients may not be high enough to warrant the use of cytoreductive therapy. Although effective in controlling vasomotor symptoms, aspirin therapy has not been shown to influence the risk of either recurrent thrombosis or first-trimester miscarriage in ET. Recent laboratory studies have suggested that hematopoiesis in ET may not always be clonal. Similarly, there is substantial heterogeneity in both megakaryocyte/platelet surface expression of the thrombopoietin receptor (c-Mpl) and bone marrow microvessel density. Clinicopathologic correlates to these biologic parameters are currently being defined.

Medical management of a large aortic thrombus in a young woman with essential thrombocythemia

Aortic thrombus formation is rare in the patients with essential thrombocytosis (ET); therefore, no guidelines for its management have been established. Embolism from ET-associated large vessel thrombi is potentially lethal and has been managed surgically in a few reported cases. We describe herein a 45-year-old black woman with ET found to have a 3.5-cm, pedunculated intra-aortic thrombus at the thoracoabdominal junction. How to treat this potentially devastating aortic thrombus was a management dilemma. We believed, based on the patient's diagnosis of ET and the histology of similar thrombi in 1 reported series, that the aortic thrombus was a "white thrombus" consisting primarily of aggregated platelets with a minimal fibrin network and almost no entrapped erythrocytes. The patient was treated with aspirin, 325 mg daily, as a platelet antiaggregating agent and hydroxyurea, 1,500 mg daily, to reduce the platelet count to less than 450 x 10(9)/L. The thrombus resolved without severe thromboembolic events. To our knowledge, this is the first reported case of a large intra-aortic thrombosis associated with ET that has been successfully managed with medical therapy alone.

Extreme Thrombocytosis after Penetrating Femoral Venous Injury

Lower extremity trauma is an uncommon cause of reactive thrombocytosis. A 17-year-old male patient with an extreme increase in platelet count caused by penetrating femoral venous injury is presented. During his stay in hospital, two thrombotic attacks were observed. Such events should be considered as high risk for thrombosis and anticoagulant therapy administered.