Mild eosinophilia with values of less than 1000 eosinophils/µL is commonly seen in the clinical practice and can be secondary to parasitic, inflammatory or allergic diseases or to drug reactions. Additionally, eosinophilia may be due to connective tissue disorders, infections and occasionally to hematopoietic malignancies or solid tumors. The criteria established in the 1970s, for the definition of idiopathic hypereosinophilic syndrome is today unsatisfactory to characterize all conditions described as eosinophilia. Now these conditions are better understood due to the evolution of cellular and molecular biology. This knowledge has helped to characterize distinct disorders involving myeloid and lymphoid lineages. Hence, eosinophilia is categorized as reactive, clonal or idiopathic. With the introduction of anti-tyrosine kinase (imatinib mesylate) therapy, which is effective for the FIP1L1/PDGFRa rearrangement, there is a possibility to control or cure chronic eosinophilic leukemia. For this reason, precise and fast diagnosis is necessary for ideal therapeutic decisions before organic lesions that are irreversible, such as heart injury, become established. The aim of this manuscript is to review eosinophilia and offer an update on diagnostic and therapeutic investigations.
Leukemia, eosinophilic, acute; Receptor, platelet-derived growth factor alpha; Receptor, platelet-derived growth factor beta; Receptors, fibroblast growth factor; Fusion proteins, bcr-abl; Hypereosinophilic syndrome
