Blood eosinophilia: a new paradigm in disease classification, diagnosis, and treatment.
Acquired blood eosinophilia is considered either a primary or a secondary phenomenon. Causes of secondary (ie, reactive) eosinophilia include tissue-invasive parasitosis, allergic or inflammatory conditions, and malignancies in which eosinophils are not considered part of the neoplastic process. Primary eosinophilia is classified operationally into 2 categories: clonal and idiopathic. Clonal eosinophilia stipulates the presence of either cytogenetic evidence or bone marrow histological evidence of an otherwise classified hematologic malignancy such as acute leukemia or a chronic myeloid disorder. Idiopathic eosinophilia is a diagnosis of exclusion (ie, not secondary or clonal). Hypereosinophilic syndrome is a subcategory of idiopathic eosinophilia; diagnosis requires documentation of both sustained eosinophilia (absolute eosinophil count > or = 1500 cells/microL for at least 6 months) and target organ damage (eg, involvement of the heart, lung, skin, or nerve tissue). Genetic mutations involving the platelet-derived growth factor receptor genes (PDGFR-alpha and PDGFR-beta) have been pathogenetically linked to clonal eosinophilia, and their presence predicts treatment response to imatinib. Accordingly, cytogenetic and/or molecular investigations for the presence of an imatinib-sensitive molecular target should accompany current evaluation for primary eosinophilia. In the absence of such a drug target, specific treatment is dictated by the underlying hematologic malignancy in cases of clonal eosinophilia; however, the initial treatment of choice for symptomatic patients with hypereosinophilic syndrome is prednisone and/or interferon alfa.
Tefferi
Ayalew
A
Department of Internal Medicine and Division of Hematology, Mayo Clinic College of Medicine, Rochester, Minn 55905, USA. tefferi.ayalew@mayo.edu
D001549:Benzamides; D004802:Eosinophilia / Q000145:classification* / Q000175:diagnosis / Q000188:drug therapy* / Q000209:etiology; D006801:Humans; D000068877:Imatinib Mesylate; D010879:Piperazines / Q000627:therapeutic use; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D011743:Pyrimidines / Q000627:therapeutic use
D001549:Benzamides; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D000068877:Imatinib Mesylate