Idiopathic hypereosinophilic syndrome and "eosinophilic leukemia".

We report a case of idiopathic hypereosinophilia syndrome (H.E.S.) with a pronounced myeloproliferative disorder, which during the course of the illness has exceeded more than one "blastic crisis". This again proposes the difficult relationship between H.E.S. and myeloproliferative syndromes (M.S.), and is indicative of why some cases of H.E.S. are differentially diagnosed as chronic myeloid leukemia (C.M.L.) with an eosinophilic component.