[Hypereosinophilia: focus on clinical aspects]

Hypereosinophilia may be associated with various clinical disorders. The severity of hypereosinophilia may be related to the underlying disease or to the possible deleterious effects of the eosinophils infiltrating most of the tissues, particularly the heart and the nervous system. Adverse reactions to drugs or other immunoallergic disorders are most often encountered. Among the parasitic diseases, helminthic infestations are especially incriminated. Cancers, autoimmune diseases and some T lymphoproliferative disorders represent the other reported conditions associated with hypereosinophilia. The detection of interleukin-5 (the most important cytokine involved in the control of eosinophils production and maturation) may contribute to the knowledge of some pathological hypereosinophilic disorders. In the absence of a well defined responsible factor, the idiopathic hypereosinophilic syndrome will be considered. The pathogenic role of a T lymphocyte disorder need to be considered in some cases.