title: Essential thrombocytosis: underemphasized cause of large-vessel thrombosis.
abstract: OBJECTIVE
  The purpose of this study was to describe the clinical course of patients seen with large-vessel thrombosis in association with essential thrombocytosis (ET).
  
  
  METHODS
  This study was a retrospective review of all patients treated for large-vessel thrombosis caused by ET during a 2-year period at University of Washington teaching hospitals.
  
  
  RESULTS
  Five patients presented with arterial (femoral-popliteal-tibial: aortic), portal (two cases), or systemic venous (inferior vena cava) thrombosis and required operation. Two were known to have ET; in three others ET was diagnosed after operation when platelet counts persistently in excess of 500,000/mm3 were noted. The diagnosis of ET was established in each case by ruling out causes of reactive thrombocytosis and (in the three new cases) by evidence for megakaryocyte hyperplasia on bone marrow biopsy. Platelet counts in all five patients were reduced to normal levels by cytoreductive therapy, and no further thrombotic episodes have occurred during 18 months (mean) of follow-up. During this 2-year period ET accounted for more large-vessel thrombotic complications in our institutions than all other more frequently described hypercoagulable states combined.
  
  
  CONCLUSIONS
  ET is an underemphasized cause of large-vessel thrombosis.
authors.affiliation: Department of Surgery, University of Washington School of Medicine, Seattle, USA.
authors.forename: M
authors.initials: M
authors.lastname: Johnson
authors.forename: T
authors.initials: T
authors.lastname: Gernsheimer
authors.forename: K
authors.initials: K
authors.lastname: Johansen
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013922:Thrombocytosis / Q000150:complications* / Q000175:diagnosis / Q000628:therapy; D013927:Thrombosis / Q000209:etiology* / Q000601:surgery