PURPOSE OF REVIEW: Eosinophils play an important role in the pathogenesis of 
allergic, infectious and malignant diseases. Over the last decade, new 
diagnostic tools and treatment modalities have led to the re-evaluation of the 
existing definition of eosinophilic disorders. This review discusses a recent 
proposal for new terminology and classification of hypereosinophilia. The 
results of targeted therapy for hypereosinophilia-related disorders are also 
summarized.
RECENT FINDINGS: A panel of multidisciplinary experts agreed on unifying 
definitions and criteria of eosinophilia-associated disorders and created a new 
classification of hypereosinophilia-related conditions based on clinical, 
haematological and laboratory findings as well as the underlying cause of 
hypereosinophilia. Recent results of the treatment of idiopathic 
hypereosinophilic syndrome (HES) with the anti-interleukin 5 monoclonal antibody 
mepolizumab showed its efficacy and manageable safety profile. The treatment of 
platelet-derived growth factor alpha (PDGFRA)-positive HES with imatinib 
demonstrated long-lasting efficacy and low likelihood of drug resistance.
SUMMARY: The unifying terminology and definitions should aid physicians caring 
for patients with hypereosinophilia. Despite much progress, serum biomarkers 
correlate with disease severity and predict responses to treatment that are 
needed. There is also a great need for understanding and specific therapy for 
PDGFRA-negative HES.