RESUMEN
INTRODUCTION: Hypereosinophilic syndrome (HES) is a group of idiopathic disorders associated with single or multiple organ system dysfunction. HES must be distinguished from reactive eosinophilia in parasitic infections, allergic diseases, and especially from hematological diseases of clonal origin. REACTIVE EOSINOPHILIA DUE TO INFECTIOUS AND PARASITIC DISEASES: Tissue helminth infections, especially toxocariasis, cause severe and long-standing hypereosinophilia. Despite specific therapy, eosinophilia may persist for over a year after diagnosis, and decreases slowly. Other helminth infections, such as trichinellosis, strongyloidosis, and rarely taeniasis and cysticercosis may also be diagnosed in patients with eosinophilia. HEMATOLOGIC AND OTHER NEOPLASTIC DISEASES: Numerous neoplastic diseases, like Hodgkin's and other malignant lymphomas, myeloproliferative diseases, systemic mastocytosis etc., may be associated with marked eosinophilia. We had two patients with clinical and histological features resembling chronic eosinophilic leukemia, and many others with T-cell lymphoma, planocellular or adenocarcinoma etc. where eosinophilia persisted DRUG-INDUCED EOSINOPHILIA: Drugs associated with eosinophilia include penicillins, tetracyclines, especially minocycline, clarithromycin, tetrazepam, mefloquine, and many, others. Toxins associated with L-tryptophan cause eosinophilia-myalgia syndrome and toxic oil syndrome, also belonging in this group. Treatment includes drug discontinuation and administration of corticosteroids. HYPEREOSINOPHILIA WITH ORGAN DYSFUNCTION: Many severe diseases, such as sarcoidosis, Churg-Strauss syndrome, pemphigus vulgaris, eosinophilic gastrointestinal diseases, inflammatory bowel disease and many others are associated with hypereosinophilia and target organ damage, e.g. involvement of the heart, lungs, skin, or nervous tissue. CONCLUSION: Eosinophilia can be classified as either familial or acquired. Hypereosinophilic syndrome is a subcategory of idiopathic eosinophilia. If the differential diagnosis of hypereosinophilia fails to resolve the etiology succesfully, the diagnosis of idiopathic HES remains.
