📊 Definitions & Approach
• Normal absolute eosinophil count (AEC): <450/μL
• Mild: 500-1500, Moderate: 1500-5000, Severe: >5000
• Most common causes: allergic disease (asthma, atopic dermatitis, allergic rhinitis), parasitic infections, drug reactions
🦠 Parasitic Causes
• Tissue-invasive helminths (not protozoa): Toxocara (visceral larva migrans), Ascaris, Strongyloides, hookworm, Trichinella, filarial worms
• Loeffler syndrome: transient pulmonary infiltrates + eosinophilia from larval migration (Ascaris, Toxocara)
• Tropical pulmonary eosinophilia: filarial infection (Wuchereria bancrofti), nocturnal wheezing, high IgE, anti-filarial antibodies
🫁 Allergic/Atopic & Drug-Induced
• Asthma (especially allergic bronchopulmonary aspergillosis - ABPA)
• Atopic dermatitis, allergic rhinitis, eosinophilic esophagitis
• Drug reaction with eosinophilia and systemic symptoms (DRESS syndrome): fever, rash, organ involvement, eosinophilia (anticonvulsants, sulfa drugs, allopurinol)
⚠️ Other Causes
• Hypereosinophilic syndrome: AEC >1500 for >6 months with end-organ damage (heart, skin, CNS), CD3-CD4+ T-cell clone or FIP1L1-PDGFRA mutation
• Immune deficiencies: Hyper-IgE syndrome (Job syndrome), Wiskott-Aldrich, Omenn syndrome (eosinophilia + erythroderma + severe combined immunodeficiency)
• Malignancy: Hodgkin lymphoma (eosinophilia), ALL with t(5;14), eosinophilic leukemia (rare)
📌 Decision strategy: History of travel, pets, atopy, medications. Tissue-invasive helminths (not protozoa) cause eosinophilia. Stool ova/parasite often negative with tissue parasites (Toxocara, Trichinella) → serology needed.