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Hypereosinophilic syndromes: Clinical manifestations, pathophysiology, and diagnosis

Florence Roufosse, MD
Amy D Klion, MD
Peter F Weller, MD, MACP
Section Editor
Bruce S Bochner, MD
Deputy Editors
Anna M Feldweg, MD
Alan G Rosmarin, MD


The hypereosinophilic syndromes (HES) are a group of disorders marked by the sustained overproduction of eosinophils, in which eosinophilic infiltration and mediator release cause damage to multiple organs. Although these disorders had long been considered idiopathic (eg, as in the "idiopathic hypereosinophilic syndrome," IHES), etiologies for some forms of HES have been described.

The clinical features, pathophysiology, and diagnosis of HES will be reviewed here. The treatment of these disorders is discussed separately, as is the initial approach to the patient with unexplained eosinophilia. (See "Hypereosinophilic syndromes: Treatment" and "Approach to the patient with unexplained eosinophilia".)


A panel of experts reached consensus on terminology pertaining to hypereosinophilic conditions and published recommendations in 2012 [1]:

Hypereosinophilia — Hypereosinophilia (HE) in the peripheral blood is defined as an absolute eosinophil count (AEC) >1.5 x 109/L (or >1500 cells/microL) on two examinations separated in time by at least one month and/or pathologic confirmation of tissue HE.

For these purposes, tissue HE is defined by:

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Literature review current through: Nov 2017. | This topic last updated: Aug 17, 2017.
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