Purpose of review: The aim of this article is to provide an update of causes of hypereosinophilia, including advances in knowledge of eosinophilic leukemia, and to outline an approach to investigation. We also aim to discuss in more detail the diagnosis and management of various hypereosinophilic syndromes including the clonal eosinophilias and those driven by abnormal cytokine-secreting T cells.
Recent findings: Our understanding of the causative genetic abnormalities in eosinophilic leukemia is increasing, as is the repertoire of techniques available to detect them. New treatments on the horizon include further tyrosine kinase inhibitors for use in eosinophilic leukemia, which should provide an alternative to imatinib for those patients who develop resistance. These may also prove useful for other hypereosinophilic syndromes without PDGFRA or PDGFRB rearrangements. Other new therapies including anti-IL5 monoclonal antibodies are proving beneficial for some patients, especially those with abnormal T-cell populations.
Summary: As our understanding of the various hypereosinophilic syndromes increases, and we are able to characterize many of the causative genetic lesions in the clonal eosinophilias, we are increasingly able to select appropriate therapy for an individual patient. New therapies based on this knowledge should serve to further improve the prognosis for many patients with hypereosinophilia.