title: MPL W515L/K Mutations in Chronic Myeloproliferative Neoplasms.
abstract: OBJECTIVE
  The MPL gene encodes the thrombopoietin receptor. Recently MPL mutations (MPL W515L or MPL W515K) were described in patients with essential thrombocythemia (ET) and primary (idiopathic) myelofibrosis (PMF). The prevalence and the clinical importance of these mutations are not clear. In the present study, we aimed to investigate the frequency and clinical significance of MPL W515L/K mutations in our patients with ET and PMF.
  
  
  METHODS
  A total of 77 patients (66 were diagnosed with ET and 11 with PMF) and 42 healthy controls were included in the study. Using peripheral blood samples, the presence of MPL W515L/K mutations and JAK-2 V617F mutation were analyzed by real-time polymerase chain reaction.
  
  
  RESULTS
  In our study, MPL W515L/K or JAK-2 V617F mutations were not observed in healthy controls. JAK-2 V617F mutation was present in 35 patients, of whom 29 had ET (43.9%, 29/66) and 6 had PMF (54.5%, 6/11). In the patient group, MPL W515L/K mutations were found in only 2 PMF cases, and these cases were negative for JAK-2 V617F mutation. The prevalence of MPL W515L/K mutations in the patient group was 2.6%, and the prevalence of MPL W515L/K mutations among the cases negative for the JAK-2 V617F mutation was found to be 4.8%. The 2 cases with MPL W515L/K mutations had long follow-up times (124 months and 71 months, respectively), had no thrombotic or hemorrhagic complications, and had no additional cytogenetic anomalies.
  
  
  CONCLUSIONS
  MPL W515L/K mutations may be helpful for identifying clonal disease in MPN patients with no established Ph chromosome or JAK-2 V617F mutation.
  
  
  BACKGROUND
  None declared.
authors.affiliation: İstanbul University, İstanbul Faculty of Medicine, Department of Internal Medicine, Division of Hematology, İstanbul, Turkey.
authors.forename: Timur Selçuk
authors.initials: TS
authors.lastname: Akpınar
authors.affiliation: İstanbul Bilim University, Faculty of Medicine, Department of Medical Biology and Genetics, İstanbul, Turkey.
authors.forename: Veysel Sabri
authors.initials: VS
authors.lastname: Hançer
authors.affiliation: İstanbul University, İstanbul Faculty of Medicine, Department of Internal Medicine, Division of Hematology, İstanbul, Turkey.
authors.forename: Meliha
authors.initials: M
authors.lastname: Nalçacı
authors.affiliation: İstanbul Bilim University, Faculty of Medicine, Department of Internal Medicine, Division of Hematology, İstanbul, Turkey.
authors.forename: Reyhan
authors.initials: R
authors.lastname: Diz-Küçükkaya
keywords: Essential thrombocythemia; JAK-2 V617F mutation; MPL W515L/K mutations; Myeloproliferative neoplasms; Primary myelofibrosis