The diagnosis of HES often involves a combination of clinical, laboratory, and histological evaluations:
Peripheral Blood Smear: Examination may reveal an elevated eosinophil count (usually >1,500 eosinophils/μL). Bone Marrow Biopsy: Histological analysis of the bone marrow can show hypercellularity with an increased number of eosinophils. Tissue Biopsy: Biopsies from affected organs may show eosinophilic infiltration and tissue damage, confirming the diagnosis.
