Eosinophilic myeloid neoplasmsNoel, Pierre; Mesa, Ruben A.Current Opinion in Hematology: March 2013 - Volume 20 - Issue 2 - p 157–162 doi: 10.1097/MOH.0b013e32835d81bf MYELOID DISEASE: Edited by Martin S. Tallman Abstract Author Information Purpose of review: In 2012, idiopathic hypereosinophilic syndrome (HES) is still the prevalent diagnosis in patients with persistent eosinophilia, in which a primary or secondary cause of eosinophilia has not been identified. HES is considered a provisional diagnosis until a primary or secondary cause of hypereosinophilia is established. The discovery of imatinib-sensitive fusion proteins in a subset of patients with hypereosinophilia has changed the way we approach the diagnosis and treatment of eosinophilic myeloid neoplasms [eosinophilic myeloproliferative neoplasms (MPNs)]. Despite the recent diagnostic developments, diagnosis of hypereosinophilic MPN is only made in 10–20% of patients with persistent primary hypereosinophilia. Recent findings: In 2008 the World Health Organization (WHO) established a semi-molecular classification of hypereosinophilic MPNs. The discovery of PDGFRA, PDGFRB, FGFR1, JAK-2, and FLT3 fusion proteins in patients with eosinophilic MPNs provide opportunities for targeted therapy. Patients with hypereosinophilic MPNs associated with PDGFRA and PDGFRB fusion genes are responsive to imatinib. Summary: Ongoing research continues to expand our understanding of the pathophysiology of persistent primary hypereosinophilia and clarify the boundaries between some of these disorders. A key challenge is to identify new targets for therapy and limit the number of patients who are classified as having HES. Division of Hematology Oncology, Mayo Clinic Arizona, Scottsdale, Arizona, USA Correspondence to Pierre Noel, MD, Division of Hematology Oncology, Mayo Clinic Arizona, 13400 East Shea Boulevard, Scottsdale, AZ 85259, USA. Tel: +1 480 301 8000; e-mail: Noel.Pierre@Mayo.edu © 2013 Lippincott Williams & Wilkins, Inc.