State of the art; the hypereosinophilic syndromes.

Many disease states such as parasitic infestations, malignancies, collagen vascular diseases, and allergies are associated with eosinophilia. The diagnosis of idiopathic hypereosinophilic syndrome (HES) requires a persistent elevation in the total eosinophil count (greater than 1500/mm3) for over 6 months, associated organ damage and no detectable underlying cause. This review provides an updated summary of the cytokine cascade that controls eosinophil production and delineates our current understanding of the clinical features of hypereosinophilic states. We also examine the central role of T-lymphocyte activation in eosinophilia, and have attempted to integrate current treatment strategies for HES with the physiology of eosinophilopoiesis.