Idiopathic hypereosinophilic syndrome.

Idiopathic hypereosinophilic syndrome is a rare but clearly defined cause of peripheral eosinophilia. The cardiovascular and hematopoietic systems are most severely affected. The clinical manifestations are a result of eosinophilic infiltration into tissues, release of eosinophilic products, and induction of a hypercoagulable state. Treatment is aimed at reducing absolute numbers of eosinophils to prevent tissue damage and halt progression of the disease.