title: Essential versus reactive thrombocythemia in children: retrospective analyses of 12 cases.
abstract: BACKGROUND
  Essential thrombocythemia (ET) rarely occurs in the pediatric population and little is known about the clinical course and the molecular characteristics.
  
  
  METHODS
  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.
authors.affiliation: Division of Pediatric Hematology and Oncology, Department of Pediatrics and Adolescent Medicine, University of Freiburg, Germany.
authors.forename: Abeer Abd
authors.initials: AA
authors.lastname: El-Moneim
authors.forename: Christian P
authors.initials: CP
authors.lastname: Kratz
authors.forename: Silke
authors.initials: S
authors.lastname: Böll
authors.forename: Manfred
authors.initials: M
authors.lastname: Rister
authors.forename: Heike L
authors.initials: HL
authors.lastname: Pahl
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: Niemeyer
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease; D005260:Female; D006801:Humans; D053614:Janus Kinase 2 / Q000235:genetics / Q000378:metabolism; D008297:Male; D055728:Primary Myelofibrosis / Q000175:diagnosis* / Q000628:therapy; D012189:Retrospective Studies; D013920:Thrombocythemia, Essential / Q000175:diagnosis* / Q000628:therapy; D013997:Time Factors
chemical_list: C507924:JAK2 protein, human; D053614:Janus Kinase 2