[Is hypereosinophilic syndrome a potentially malignant condition?]

The existence of eosinophilic leukemia (EL) has been controversial since it was first described. Recently, some authors have suggested that EL is part of a spectrum of eosinophilic diseases termed hypereosinophilic syndrome (HS). EL diagnosis is very difficult, especially if abnormal chromosome are not present, because HS comprises multiple disease entities of unclear etiology with the common features of prolonged eosinophilia of undetectable cause and organ system dysfunction. We present a case of HS whose findings are consistent with a leukemic process. For two years the patient showed only sharp hypereosinophilia; his clinical course was then marked by signs and symptoms of granulocytic sarcoma (GS), an extramedullary tumor composed of granulocytic precursor cells. GS as a complication of EL was described and in some cases the diagnosis of leukemia was made only on the basis of the GS complication. The formation of eosinophilic GS also suggests a diagnosis of LE in our case of HS. Finally, we always consider HS as a potential malignant disease.