Eosinophilia: secondary, clonal and idiopathic

Abstract

SummaryBlood eosinophilia signifies either a cytokine-mediated reactive phenomenon (secondary) or an integral phenotype of an underlying haematological neoplasm (primary). Secondary eosinophilia is usually associated with parasitosis in Third World countries and allergic conditions in the West. Primary eosinophilia is operationally classified as being clonal or idiopathic, depending on the respective presence or absence of a molecular, cytogenetic or histological evidence for a myeloid malignancy. The current communication features a comprehensive clinical summary of both secondary and primary eosinophilic disorders with emphasis on recent developments in molecular pathogenesis and treatment.

Association of the blood eosinophil count with hematological malignancies and mortality

“…Blood eosinophilia, traditionally defined for use in clinical practice as an eosinophil count of 0.5 3 10 9 /l, is encountered in all areas of medicine and in both primary and secondary care. The degree of blood eosinophilia may be arbitrarily categorized as mild (from 0.5 3 10 9 /l and up to 1.5 3 10 9 /l), moderate (from 1.5 3 10 9 /l and up to 5.0 3 10 9 /l) and severe (from 5.0 3 10 9 /l) and may arise from either clonal intrinsic disorders or from reactive extrinsic conditions [2][3][4]. Reactive causes account for the vast majority of cases.…”

Eosinophilia in routine blood samples and the subsequent risk of hematological malignancies and death

“…The eosinophil is a multifunctional cell, which can store and secrete biologically active substances relevant for its effects in infections, allergy, and inflammation [2,3]. An increased number of eosinophils in peripheral blood (eosinophilia, >0.5 3 10 9 /L) may accompany various conditions like invasive parasitic disease, asthma, drug reactions, connective tissue diseases, or malignancies.…”

“…Rare cases of eosinophilia are classified as primary or non-reactive and arise from an autonomous cell production, caused by clonal disorders of lymphoid or myeloid origin. A residual small group of patients are termed idiopathic because the suspected clonal origin is missing [3][4][5]. Irrespective of the cause of eosinophilia, activation of eosinophils may cause a diverse organ involvement [3,5,6].…”

“…A residual small group of patients are termed idiopathic because the suspected clonal origin is missing [3][4][5]. Irrespective of the cause of eosinophilia, activation of eosinophils may cause a diverse organ involvement [3,5,6]. Thus, blood eosinophilia may arise from intrinsic eosinophilic disorders caused by cytogenetic mechanisms or extrinsic eosinophilic reactions caused by cytokines [3][4][5]7,8].…”

“…Irrespective of the cause of eosinophilia, activation of eosinophils may cause a diverse organ involvement [3,5,6]. Thus, blood eosinophilia may arise from intrinsic eosinophilic disorders caused by cytogenetic mechanisms or extrinsic eosinophilic reactions caused by cytokines [3][4][5]7,8]. Hodgkin's lymphoma (HL) is a classic example of a hematologic, extrinsic disorder accompanied by blood eosinophilia in about 15% of cases.…”