About Hypereosinophilic Syndrome
Hypereosinophilic Syndrome is defined by persistent blood eosinophilia exceeding 1,500 cells per microliter with evidence of eosinophil-mediated organ damage, encompassing heterogeneous subtypes including the FIP1L1-PDGFRA fusion-driven myeloid variant (highly responsive to imatinib), lymphocyte-variant HES (driven by aberrant IL-5-secreting T-cell clones), and idiopathic HES where no underlying cause is identified. End-organ damage from eosinophilic infiltration and granule protein deposition can affect the heart (Loeffler endocarditis), nervous system, skin, and lungs. Mepolizumab (anti-IL-5) has demonstrated efficacy and is approved for HES in patients without FIP1L1-PDGFRA.
Common Clinical Features
Clinical Trial Eligibility Tips
What to know before applying to Hypereosinophilic Syndrome trials.
HES subtype classification (myeloid/FIP1L1-PDGFRA, lymphocytic, idiopathic) determines trial eligibility; FIP1L1-PDGFRA FISH or RT-PCR testing and T-cell clonality studies are required before applying
Anti-IL-5 therapy trials (mepolizumab, benralizumab) typically exclude FIP1L1-PDGFRA positive patients who should instead be on imatinib; confirm and document fusion gene status
Cardiac screening with echocardiography is mandatory in most trials given risk of Loeffler endocarditis; provide most recent echo with ejection fraction and valvular assessment
Patient Resources
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