Approach to patients with eosinophilia.

Eosinophilia is commonly seen in medical practice and can underlie a variety of medical conditions. Eosinophilia, defined as peripheral blood eosinophil counts greater than 500 per microliter, may vary from mild-severe. Idiopathic hypereosinophilic syndrome has been identified as an unusual cause of moderate to severe eosinophilia. Progress in treatment of this condition has accompanied greater understanding about the basic biology of eosinophils. This review will highlight the approach to patients with eosinophilia, along with associated conditions and syndromes.