Hypereosinophilic Syndromes (HES)
Amy Klion, MD
National Institute of Health
Eosinophil Pathology Unit
Laboratory of Parasitic Diseases
Bethesda, Maryland USA
Hypereosinophilic syndromes (HES) are a heterogeneous group of disorders defined by the presence of peripheral eosinophilia and eosinophil-related pathology. In recent years, a number of clinical variants of HES have been described. For some of these, including PDGFRA-positive myeloproliferative neoplasm and lymphocytic variant HES, the etiology has been identified. Although this has simplified treatment and led to improved outcomes for some variants, these advances have created confusion in the definition of HES. Similarly, although the development of a wide variety of therapeutic agents targeting specific pathways or aspects of eosinophilia and eosinophil activation is adding to the armamentarium of agents available to treat patients with HES, our lack of understanding of the mechanisms of pathogenesis in the different clinical variants of idiopathic disease makes selection of the most appropriate agent for an individual patient difficult. Recent advances in HES classification and therapeutic choices will be discussed.