Eosinophil disorders

Kim, Sun Young

Abstract

Blood eosinophilia can be classified as either familial or acquired. Familial eosinophilia is a rare autosomal dominant disorder characterized by a stable eosinophil count. Acquired eosinophilia is classified further into a primary or secondary phenomenon depending on whether eosinophils are considered integral to the underlying disease. Primary eosinophilia is considered clonal in the presence of either a cytogenetic abnormality or bone marrow histological evidence of classified hematologic malignancies. Causes of secondary eosinophilia include infections, allergic or immunologic disorders, and drugs. Idiopathic eosinophilia belongs to a category of primary eosinophilia, and this is a diagnosis of exclusion. Cases with eosinophilia that lack evidence of clonality may be diagnosed as idiopathic hypereosinophilic syndrome after all causes of reactive eosinophilia have been eliminated. Genetic mutations involving the platelet-derived growth receptor genes (PDGFRA and PDGFRB) have been pathogenetically linked to clonal eosinophilia, and their presence predicts the treatment response to imatinib. In this review, I will present a clinical summary of both familial and acquired eosinophilia with emphasis on recent developments in molecular pathogenesis and treatment.