Advances in diagnosis and treatment of eosinophilia.
OBJECTIVE
Hypereosinophilic syndromes (HESs) are disorders characterized by sustained blood or tissue hypereosinophilia or both with subsequent damage to various organs due to eosinophilic infiltration and release of mediators. HES are now recognized to include varied eosinophilic disorders for some of which there are recent insights into their pathogenesis and targeted treatment.


RESULTS
Studies have helped delineate two subtypes of HES: the myeloproliferative variants of HES and the lymphocytic variants of HES. Many, but not all, myeloproliferative-HES patients have interstitial deletions on chromosome 4q12 that lead to fusion of the FIP1-like 1 and platelet-derived growth factor receptor alpha genes, with the fusion product encoding a protein that has constitutive tyrosine kinase activity. Lymphocytic-HES is a primary lymphoid disorder characterized by nonmalignant expansion of a T-cell population able to produce eosinophilopoietic cytokines, with the T-cell population being identified by flow cytometry or reverse transcriptase-PCR for T-cell receptor usage or both. Other HES subtypes are of uncertain causes and are included in recent diagnostic algorithms for the spectrum of HES.


CONCLUSIONS
The contemporary definition of the hypereosinophilic syndromes encompasses a range of eosinophilic disorders characterized by chronic blood hypereosinophilia often with eosinophil-mediated damage to various organs.
Sheikh
Javed
J
Division of Allergy and Inflammation, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA. jsheikh@bidmc.harvard.edu
Weller
Peter F
PF
D003936:Diagnosis, Computer-Assisted; D004802:Eosinophilia / Q000175:diagnosis* / Q000628:therapy*; D006801:Humans; D017681:Hypereosinophilic Syndrome / Q000145:classification / Q000175:diagnosis / Q000209:etiology* / Q000628:therapy; D007960:Leukocyte Disorders; D009196:Myeloproliferative Disorders