[Idiopathic hypereosinophilic syndrome. Current clinico-therapeutic state]

Idiopathic hypereosinophilic syndrome is a term labelling clinical illnesses characterized by blood hypereosinophilia and widespread infiltration of organs and tissues by mature eosinophils. Although any tissue can be affected the involvement of the nervous system and of the myocardium usually indicates worse prognosis. Histopathological studies carried out on myocardial tissues of hypereosinophilic patients, suggest that eosinophils are the main inducers of tissue damages. These cells seem to affect first the coronary endothelial cells, so leading to thrombi formation and then fibrosis. Eventually restrictive cardiomyopathy may occur. The pathogenetic events are not fully understood. However several studies have been focused on two eosinophil proteins: the major basic protein (MBP) as possible mediator of tissue damages and the cationic eosinophil protein (ECP) involved in thrombotic events. In the bone marrow a marked hyperplasia of the eosinophil series is usual, while in the blood only mature eosinophils circulate. Non specific abnormalities either of the cellular or humoral immunity have been described. Previous reports of a definitely incurable disease have been improved by modern therapeutic programs.