Criteria

• WBC > 25, predominantly segs and bands (over 80%)
  • immature forms < 10%
  • blasts < 1%
• hypercellular marrow
  • increased neutrophilic lineage but normal maturation
  • blasts < 5%
• hepatosplenomegaly
• diagnosis of exclusion, rule out:
  • reactive neutrophilia (clonality)
  • CML (Bcr-Abl)
  • other MPNs: PCV, PMF, ET
  • MDS
  • PDGFRA, PDGFRB, FGFR1