Thrombocytosis in children with Hemophilus influenzae meningitis

A retrospective study of thrombocytosis in children with Hemophilus influenzae meningitis was performed. Forty-five percent of patients had a platelet count greater than 500 X 10(9)/l during hospitalization. The mean platelet count was 284 X 10(9)/l on admission, and gradually increased to 648 X 10(9)/l on day 11 of hospitalization. These results document that thrombocytosis is common among children with H. influenzae meningitis and suggest that it is probably a recovery phenomenon.     

Thrombocytosis Associated with Solid Tumors in Children

The association between thrombocytosis and malignant disease was first described by Levin and Conley in 1964¹ but its pathogenesis remains unknown. We have studied the platelet counts in 108 children with solid tumors presenting to this hospital over the last 5 years. Thrombocytosis was defined as a platelet count over 400 × 10⁹/L and was noted in 43 children (40%) at presentation; in the great majority of cases the thrombocytosis could not be ascribed to infection or hemorrhage. The platelet counts in relation to the six commonest diagnoses are shown in Figure 1. The association was particularly marked in the case of hepatic tumors, where 8 out of 10 patients had platelet counts at presentation above 400 × 10⁹/L with a mean of 647 ± 306 (SD) × 10⁹/L (range 294-1310). Thrombocytopenia (platelet count less than 150 × 10⁹/L) was noted in 5 children at presentation; 2 of these had morphological evidence of bone marrow infiltration.     

Thrombocytosis Associated with Solid Tumors in Children

The association between thrombocytosis and malignant disease was first described by Levin and Conley in 1964¹ but its pathogenesis remains unknown. We have studied the platelet counts in 108 children with solid tumors presenting to this hospital over the last 5 years. Thrombocytosis was defined as a platelet count over 400 × 10⁹/L and was noted in 43 children (40%) at presentation; in the great majority of cases the thrombocytosis could not be ascribed to infection or hemorrhage. The platelet counts in relation to the six commonest diagnoses are shown in Figure 1. The association was particularly marked in the case of hepatic tumors, where 8 out of 10 patients had platelet counts at presentation above 400 × 10⁹/L with a mean of 647 ± 306 (SD) × 10⁹/L (range 294-1310). Thrombocytopenia (platelet count less than 150 × 10⁹/L) was noted in 5 children at presentation; 2 of these had morphological evidence of bone marrow infiltration.     

Mechanism of Thrombocytosis in Hepatoblastoma: A Case Report

Although thrombocytosis has long been recognized as a common finding in children with hepatoblastoma, its mechanism is still unknown. In this study, to confirm the role of throm-bopoietin (Tpo) in the thrombocytosis in hepatoblastoma, the expression of Tpo mRNA in tumor cells was examined and the serum Tpo level was analyzed during the course of the disease. A 1-year, 6-month-old girl was diagnosed as having advanced hepatoblastoma. At diagnosis, she had marked thrombocytosis with 1220 × 10⁹μlL. After resection of the tumor and after four courses of chemotherapy, the level of α-fetoprotein normalized but the platelet count remained high. However, after the fifth course of chemotherapy, the platelet count decreased and normalized within 3 months. By enzyme-linked immunosorbent assay, the serum Tpo level was not high at diagnosis, whereas high Tpo levels were observed after chemotherapy. By polymerase chain reaction, Tpo mRNA was detected in both normal liver and tumor tissues, but the level of expression was not different between them. Therefore, in hepatoblastoma the serum Tpo level is not correlated with a high platelet count, and there is no difference in Tpo expression between normal liver and tumor tissues. Other unknown factors and their production sites to induce thrombocytosis should be examined in further studies.     

Thrombocytosis in children

In healthy pediatric subjects normal count platelet ranges between 250,000 μL and 450,000 μL. An elevated platelet count greater than 2 SD defines a condition of thrombocytosis. On a clinical level, thrombocytosis is classified "mild" at a platelet count between >500,000 μL and <700,000 μL; "moderate" at a platelet count between >700,000/μL and <900,000/μL; "severe" at a platelet count >900,000/μL; and "extreme" at a platelet count >1,000,000/μL. Thrombocytosis can be classified as primary or secondary. Primary thrombocytosis is divided into familial and essential. Primary thrombocytosis is an extremely rare clonal disease in childhood with incidence of one per million children, i.e., 60 times lower than in adults. It is classified as a myeloproliferative disorder with polycythemia vera, chronic myeloid leukaemia and myelofibrosis and may be associated with thrombotic or haemorrhagic events. Platelet count is generally above 1,000,000/μL. The median age at diagnosis is about 11 years. On the contrary, secondary or reactive thrombocytosis (RT) is very common in pediatric age, occurring in 3-13% of hospitalized children because of several causes. Generally, it is a reactive process caused by infection, chronic inflammation, iron deficiency, tissue damage, cancer, drugs and surgical or functional splenectomy. Thrombocytosis is mild in 72-86% of children, moderate in about 6-8%, and extreme in 0.5-3%. Consultation with a pediatric hematologist is required if elevation of platelet count persists, is unexplained or symptomatic. In the majority of cases no treatment is necessary, and the patient must be only closely monitored.     

Essential versus reactive thrombocythemia in children: retrospective analyses of 12 cases

BACKGROUND: Essential thrombocythemia (ET) rarely occurs in the pediatric population and little is known about the clinical course and the molecular characteristics. PROCEDURE: In this retrospective multi-institutional study we examine the clinical, hematological, and molecular features of 12 children aged 5-16 years with thrombocytosis and a suspected diagnosis of ET. RESULTS: Median follow-up was 59 months (range 10-72). Seven patients presented with clinical symptoms potentially related to thrombocytosis. The remaining five patients were diagnosed incidentally. Median platelet count at diagnosis was 1,325 x 10(9)/L (range 600-3,050). In 11 out of 12 cases bone marrow morphology was consistent with ET, the remaining patient had chronic idiopathic myelofibrosis. Cytogenetic analyses were normal in all studied cases and only one out of nine analyzed cases harbored a JAK(V617F) allele. Within 6 months after initial presentation one patient who was initially asymptomatic developed thrombosis and another patient had mild bleeding. Eight patients were treated with acetylsalicylic acid, one patient received hydroxyurea, and two patients received anagrelide. At last follow-up, all patients were alive and none had developed leukemia. Five patients experienced hematological remission. Two children had not received any therapy. During the course of their disease, nine patients developed symptoms possibly attributable to an elevated platelet count. CONCLUSIONS: In JAK2 mutation negative cases, long-term follow-up is helpful to distinguish between primary and secondary thrombocytosis. Secondary cases are not associated with organomegaly but may present with unspecific symptoms. Indications for treatment in children remain unclear.     

Secondary thrombocytosis

To estimate the incidence and causes of secondary thrombocytosis in children, a 12 month study of all patients attending a children's hospital and discovered to have a platelet count over two times the upper normal limit (> 800 x 10(9)/l) was undertaken. Data so obtained were analysed both separately and together with those from two previous studies to gain as broad a perspective as possible. Of 7916 children who had platelet counts during the study period, 36 (0.5%) produced a value > 800 x 10(9)/l; there were 19 boys and 17 girls. There was a preponderance of young infants (median age 13 months). Twenty seven of the 36 had some sort of associated infection, bacterial in 18 and viral in nine. The other nine were either recovering from anti-neoplastic chemotherapy (n = 6), were post-operative (n = 2), or simply iron deficient (n = 1). Combining these patients with those described in previous studies allowed a review of 139 unselected children with very high platelet counts. Fifty three (38%) had infections, 29 (20%) had traumatic or surgical tissue damage, 16 (11%) had malignant disease undergoing chemotherapy or surgery, and 13 (9%) had connective tissue or autoimmune disorders. Secondary thrombocytosis is not rare and is most frequently seen in very young infants after infection. It can arise in a wide variety of other circumstances including rebound from myelosuppression, iron lack, or as part of an acute phase response. It is clinically unimportant in terms of morbidity and requires no treatment other than that for the primary condition.     

Essential thrombocythemia in a child with elevated thrombopoietin concentrations and skeletal anomalies

Essential thrombocythemia is a rare myleoproliferative disorder in pediatrics. This myleoproliferative disorder is characterized by excessive proliferation of megakaryocytes and sustained elevation of platelet count. Reactive thrombocytosis is a more common cause of elevated platelet counts among children. We describe a 2-year-old child with essential thrombocythemia, skeletal anomalies, and elevated thrombopoietin concentrations. The child's mother was also subsequently diagnosed with essential thrombocythemia and had elevated thrombopoietin concentrations. Chromosomal studies on the mother, child and other family members were normal.     

Extreme thrombocytosis in admissions to paediatric intensive care: no requirement for treatment

Extreme thrombocytosis (ExtThr; platelet count > or =1000x10(9)/l) is uncommon but may have an increased occurrence in critically ill children. The incidence of ExtThr for children on the Paediatric Intensive Care Unit at Bristol Royal Hospital for Children between January 2001 and December 2004 was calculated, and the notes of children identified with ExtThr were reviewed for possible common aetiological factors, potential treatment regimes and outcome.     

Extreme thrombocytosis in admissions to paediatric intensive care: no requirement for treatment.

Extreme thrombocytosis (ExtThr; platelet count > or =1000x10(9)/l) is uncommon but may have an increased occurrence in critically ill children. The incidence of ExtThr for children on the Paediatric Intensive Care Unit at Bristol Royal Hospital for Children between January 2001 and December 2004 was calculated, and the notes of children identified with ExtThr were reviewed for possible common aetiological factors, potential treatment regimes and outcome.     

Thrombocytosis in pediatric HIV infection

Thrombocytopenia has been extensively reported in association with HIV infection. Twenty-four children (6%) from a cohort of 400 children with platelet counts >500,000/mm(3) were reviewed. All had symptomatic disease and 10 (42%) patients died. In 4 children the platelet count exceeded 700,000/mm(3) and in 1 patient the platelet count was 1.5 million/mm(3). There were no thrombotic complications, and no specific therapy was required for the thrombocytosis. Thus HIV-1 infection, a chronic viral infection, is another etiologic agent for thrombocytosis and is associated with severe disease.     

Secondary thrombocytosis.

To estimate the incidence and causes of secondary thrombocytosis in children, a 12 month study of all patients attending a children's hospital and discovered to have a platelet count over two times the upper normal limit (> 800 x 10(9)/l) was undertaken. Data so obtained were analysed both separately and together with those from two previous studies to gain as broad a perspective as possible. Of 7916 children who had platelet counts during the study period, 36 (0.5%) produced a value > 800 x 10(9)/l; there were 19 boys and 17 girls. There was a preponderance of young infants (median age 13 months). Twenty seven of the 36 had some sort of associated infection, bacterial in 18 and viral in nine. The other nine were either recovering from anti-neoplastic chemotherapy (n = 6), were post-operative (n = 2), or simply iron deficient (n = 1). Combining these patients with those described in previous studies allowed a review of 139 unselected children with very high platelet counts. Fifty three (38%) had infections, 29 (20%) had traumatic or surgical tissue damage, 16 (11%) had malignant disease undergoing chemotherapy or surgery, and 13 (9%) had connective tissue or autoimmune disorders. Secondary thrombocytosis is not rare and is most frequently seen in very young infants after infection. It can arise in a wide variety of other circumstances including rebound from myelosuppression, iron lack, or as part of an acute phase response. It is clinically unimportant in terms of morbidity and requires no treatment other than that for the primary condition.     

Thrombocytosis in an infant with high thrombopoietin concentrations

Patients with essential thrombocythemia (ET) usually have normal thrombopoietin (TPO) concentrations because of negative feedback from thrombocytosis. TPO mutations in familial ET cases result in increased translation efficiency with excessive TPO stimulation and thrombocytosis. The authors describe an infant with a high platelet count (1300 x 103/mm3) and an elevated TPO concentration who was successfully treated with anagrelide. Sequencing of TPO revealed no genetic cause. This case may represent a case of atypical ET in which thrombocytosis results from TPO stimulation rather than clonal proliferation. Measuring TPO concentrations may be warranted for children with unexplained extreme thrombocytosis.     

Neonatal thrombocytosis resulting from the maternal use of non-narcotic antischizophrenic drugs during pregnancy

Neonatal thrombocytosis can result from maternal narcotic drug abuse. The case of a male infant is reported who was born to a woman with schizophrenia treated with non-narcotic psychotropic drugs during pregnancy; he developed severe prolonged thrombocytosis. The platelet count reached 1310 x 10(9)/l on day 15. This thrombocytosis persisted for three months. The patient was treated with dipyridamole. A bone marrow aspirate showed normal myeloid and erythroid precursors with an increased number of megakaryocytes. Plasma concentrations of interleukin 6 and thrombopoietin were suppressed. No obvious complications from the thrombocytosis occurred, and the platelet count fell to within the upper limit of normal after 3 months of age. This case indicates that thrombocytosis may occur in infants born to mothers treated with non-narcotic psychopharmaceutical drugs during pregnancy. The thrombocytosis in this case may have been induced by factors other than interleukin 6 or thrombopoietin.     

Platelet serotonin concentration in children under 5 years of age]

High platelet serotonin concentrations have been reported in children with early infantile autism. However, as yet there are no reference values regarding platelet serotonin in normal infants and young children so that it remains difficult to define the exact significance of this finding. We report here with the platelet serotonin concentration found in 57 infants and children (20 girls, 37 boys) ranging in age from 10 days to 5 years old. Our results show that mean platelet serotonin concentrations in infants and young children are significantly greater than mean values obtained in older children (+11%) and neonates in the umbilical cord (+64%). No significant variations were found relating to sex, leucocyte count and platelet count. There therefore appears to be a physiological elevation of platelet serotonin concentration in infants and young children, and this has to be taken into consideration in the interpretation of the elevated values found in cases of infantile autism.     

Thrombocytosis at an early stage of respiratory tract viral infection

AIM: To determine whether thrombocytosis, a platelet count of more than 500 x 10(9)/l, occurs at an early stage of respiratory tract viral infection. METHODS: The medical records of 345 patients with respiratory syncytial virus (RSV), influenza, measles, adenovirus or human herpes virus 6 infections were retrospectively reviewed. RESULTS: The mean platelet count was significantly higher in RSV patients than in patients with other respiratory infections. Among the 29 patients with thrombocytosis, 24 (82.8%) had RSV infection. CONCLUSION: When thrombocytosis is positive at an early stage of respiratory tract infection, RSV should be taken into account as a causative agent.     

Reactive thrombocytosis in children with upper urinary tract infections

The relationship between reactive thrombocytosis and the level of urinary tract infections was studied in 48 children. Platelets were counted before, during and after treatment. Reactive thrombocytosis was noticed in 74% of children with upper and in 14% with lower urinary tract infections. A significant rise in the platelet count presented in another five children (15%) with upper urinary tract infections. Conclusion: Reactive thrombocytosis was found almost exclusively in the renal parenchymal infections, usually during the recovery phase.     

Tremors and thrombocytosis during treatment of megaloblastic anaemia

In developing countries, a deficiency of cobalamine and folate contributes significantly to megaloblastic anaemia. Neurological observations in infants and young children with megaloblastic anaemia have included hypotonia, developmental regression, tremors and other abnormal movements. Following therapy with vitamin B12, coarse tremors occurred in six of 51 patients (12%) with megaloblastic anaemia. The tremors, which were noticed initially in the hands and feet, gradually became generalised and disappeared during sleep. They subsided within 5-11 days. Thirteen of 25 (52%) patients developed thrombocytosis between day 3 and week 5 of follow-up. In one child, the platelet count increased to >1300 x 10(9)/L. The importance of recognising these clinical findings during treatment of megaloblastic anaemia is emphasised.     

Thrombocytosis after pneumonia with empyema and other bacterial infections in children

Thrombocytosis is seen in association with many conditions, including infectious diseases. We studied thrombocytosis after severe bacterial infections, particularly pneumonia with empyema in children. A systematic survey of the phenomenon was conducted. Twenty-seven children admitted for pneumonia with empyema were studied. Thrombocytosis (platelet counts greater than 500 x 10(3)/microliters) was present in 92.5%. Platelet counts reached their maximum at 15.1 +/- 3.7 days (range, 7 to 25) and declined to normal after 3 weeks of illness. Compared with a healthy control group, significant thrombocytosis, but of lower incidence, was also noted in children with lobar pneumonia without pleural effusion, bacterial meningitis and osteomyelitis. Platelet functions were examined in seven of the children but no abnormalities were observed. Bone marrow aspiration of three children with pneumonia and empyema showed megakaryocytic hyperplasia. We found no correlation between thrombocytosis, neutrophilia, fever, the clinical course, complications, prognosis or treatment. Neither thromboembolic nor hemorrhagic phenomena were observed.     

川崎病患儿外周血中红细胞和血小板参数的变化

川崎病（KD）是一种以全身血管炎为主要病理改变的急性发热、出诊性疾病：多数患儿还可以出现贫血、血小板数升高等改变。本文通过全自动血细胞计数仪对KD患儿的外周血红细胞和血小板参数的观察，发现其贫血患儿的平均红细胞体积（MCV）降低、红细胞分布宽度（RDW）增高，为小细胞不均一性贫血，符合缺铁性贫血的表现。KD患儿血小板数普遍较高，尤其病程早期的平均血小板体积（MPV）增高，提示有血小板增多的趋势和在血管炎性反应中的重要作用。因此，对KD患儿应尽早使用抗血小板药物，在治疗过程中注意对缺铁性贫血的纠正。