Eosinophilia Diagnosis and Management

Introduction to Eosinophilia

The most common causes of elevated eosinophils are allergic disorders (approximately 80% of cases), followed by parasitic infections, with tissue-invasive helminths being the primary parasitic culprits 1, 2

The evaluation must distinguish between secondary (reactive) eosinophilia and primary (neoplastic) eosinophilia based on the degree of elevation and clinical context 2

Allergic conditions, including allergic asthma, food allergy, atopic dermatitis, and drug reactions, account for the vast majority of cases 1, 3
Parasitic infections, particularly Strongyloides stercoralis, represent the second most common cause and require stool examination for ova and parasites plus serology if gastrointestinal symptoms or travel history is present 1, 2, 3
Medication reactions should be evaluated through comprehensive medication review, including recent additions or changes 3
Immune checkpoint inhibitor therapy can cause eosinophilia as part of immune-related adverse events 3

For persistent elevations ≥1500 cells/μL lasting more than 3 months, refer to hematology immediately and assess for organ damage 2, 3
Myeloid/lymphoid neoplasms with tyrosine kinase fusion genes (PDGFRA, PDGFRB, FGFR1, JAK2) require bone marrow biopsy, cytogenetics, FISH, and RT-PCR 1, 2
Hypereosinophilic syndrome (HES) affects skin, lungs, gastrointestinal tract, heart, and nervous system, with endomyocardial involvement particularly concerning 1, 4
Eosinophilic granulomatosis with polyangiitis (EGPA) presents with asthma, nasal polyposis, and systemic vasculitis, though only 30-40% are ANCA-positive 4

Eosinophilic esophagitis (EoE) causes tissue eosinophilia (≥15 eos/hpf) but peripheral blood eosinophilia occurs in only 10-50% of adults and 20-100% of children, typically with modest 2-fold elevations 5, 6, 7, 8
EoE requires symptoms of esophageal dysfunction plus exclusion of GERD, hypereosinophilic syndrome, Crohn's disease, infections, connective tissue disorders, and drug hypersensitivity 5, 6
50-80% of EoE patients have concurrent atopic conditions (allergic rhinitis, asthma, atopic dermatitis) which may independently contribute to peripheral eosinophilia 7, 8

Obtain complete blood count with differential, serum chemistries, vitamin B12 levels, and serum immunoglobulin levels for all patients with confirmed eosinophilia 2, 3, 9
Inflammatory markers (C-reactive protein, erythrocyte sedimentation rate) and urinalysis with protein assessment are also recommended 2, 3

For hypereosinophilia, systematically evaluate for end-organ involvement, including cardiac assessment with echocardiography or cardiac MRI, pulmonary function tests, chest imaging, endoscopy with biopsies, skin biopsy, and neurological evaluation with imaging if necessary 2