What is the hypereosinophilic syndrome (HES)?

• Blood eosinophilia is defined as peripheral blood eosinophil count > 0.5 × 10 ⁹/L.
• Blood hypereosinophilia is persistent eosinophil count > 1.5 × 10⁹/L on 2 examinations over ≥ 1 month without evidence of organ damage.
• Hypereosinophilic syndrome is hypereosinophilia of any cause (reactive or clonal) associated with clear evidence of hypereosinophilia-related organ damage.

Learn more here.