title: Frequency and clinical features of the JAK2 V617F mutation in pediatric patients with sporadic essential thrombocythemia.
abstract: BACKGROUND
  Pediatric essential thrombocythemia (ET) is a rare and heterogenous disease entity. While several recent studies have focused on the role of the JAK2 V617F mutation in pediatric ET, the frequency of pediatric ET cases with this mutation and the associated clinical features remain unclear.
  
  
  METHODS
  We examined six childhood cases who had been diagnosed with ET according to WHO criteria (onset age: 0.2-14 years) for the presence of the JAK2 V617F mutation, MPLW515L mutation and JAK2 exon 12 mutations. Two sensitive PCR-based methods were used for the JAK2 V617F genotyping. We also examined the expression of polycythemia rubra vera-1 (PRV-1), which is a diagnostic marker for clonal ET.
  
  
  RESULTS
  We found that three of the six cases had the JAK2 V617F mutation and that all six cases expressed PRV-1 in their peripheral granulocytes. Neither MPL W515L mutation nor JAK2 exon 12 mutations was detected in the patients without JAK2 V617F mutation. The two patients who developed thrombocythemia during infancy were JAK2 V617F-negative.
  
  
  CONCLUSIONS
  These findings suggest that the JAK2 V617F mutation is not rare in childhood sporadic ET cases, and that these cases might be older and myeloproliferative features.
authors.affiliation: Department of Pediatrics, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Kyoto, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Nakatani
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Imamura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ishida
authors.forename: Katsuji
authors.initials: K
authors.lastname: Wakaizumi
authors.forename: Tohru
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Otabe
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Ishigami
authors.forename: Souichi
authors.initials: S
authors.lastname: Adachi
authors.forename: Akira
authors.initials: A
authors.lastname: Morimoto
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005091:Exons / Q000235:genetics; D005260:Female; D058851:GPI-Linked Proteins; D006801:Humans; D007223:Infant; D007519:Isoantigens / Q000097:blood / Q000235:genetics; D053614:Janus Kinase 2 / Q000235:genetics*; D008297:Male; D008562:Membrane Glycoproteins / Q000097:blood / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D009504:Neutrophils; D016133:Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000097:blood / Q000235:genetics; D013920:Thrombocythemia, Essential / Q000097:blood / Q000175:diagnosis / Q000235:genetics*
chemical_list: D015415:Biomarkers; C407242:CD177 protein, human; D058851:GPI-Linked Proteins; D007519:Isoantigens; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C507924:JAK2 protein, human; D053614:Janus Kinase 2