Approach to Hypereosinophilia

Initial Assessment and Risk Stratification

The American College of Cardiology recommends that any patient with evidence of end-organ damage requires urgent medical assessment and consideration of emergency treatment regardless of eosinophil count 1
Hypereosinophilia is defined as peripheral blood eosinophil count >0.5 × 10⁹/L, with significant hypereosinophilia at ≥1.5 × 10⁹/L, according to the Journal of Infection 1
Persistent eosinophilia ≥1.5 × 10⁹/L for more than 3 months without end-organ damage warrants hematology referral after infectious causes are excluded or treated, as per the guidelines 1

Cardiac involvement (Löeffler endocarditis) presents with myocardial fibrosis, systemic thromboembolism, and acute heart failure—the primary cause of mortality in hypereosinophilic syndromes, as reported in Circulation 2
Eosinophilic myocarditis progresses through three stages: necrotic, thrombotic, and fibrotic, according to the American Heart Association, with high thromboembolism risk in the thrombotic stage 2
Echocardiography and cardiac MRI are helpful, but myocardial biopsy remains the gold standard for diagnosis, as stated in the Circulation journal 2

Helminths are the most common identifiable cause of eosinophilia in returning travelers or migrants, with diagnosis rates of 19-80%, according to the Journal of Infection 1
Critical helminth to identify: Strongyloides stercoralis can persist lifelong and present as hyperinfection syndrome with high mortality in immunocompromised patients, as warned by the Journal of Infection 1
Schistosoma haematobium is associated with squamous cell bladder carcinoma, as reported in the Journal of Infection 1

Empirical treatment for asymptomatic eosinophilia in those aged >24 months: albendazole 400 mg single dose plus ivermectin 200 μg/kg single dose, as recommended by the Journal of Infection 1
For Hypereosinophilic Syndrome with Cardiac Involvement, corticosteroid therapy is generally considered primary therapy for eosinophilic myocarditis, though efficacy is not well supported, as reported in Circulation 2

Refer to hematology if eosinophilia ≥1.5 × 10⁹/L persists for >3 months after treating infectious causes, as advised by the Journal of Infection 1
Serial cardiac imaging if cardiac involvement was present, as recommended by Circulation 2

Do not delay treatment in patients with end-organ damage—this is a medical emergency requiring prompt aggressive therapy to reduce morbidity and mortality, as warned by the Journal of Infection 1
Testing for eosinophilia alone is not adequate screening for helminth infection—many infected patients do not have eosinophilia, as reported in the Journal of Infection 1

Severe abdominal pain with hepatosplenomegaly can be a presenting symptom of eosinophilia, requiring immediate attention and empirical antiparasitic treatment in travelers/migrants 3
Respiratory distress is a critical red flag in eosinophilia, necessitating prompt evaluation and treatment 3
Reassess eosinophil count 4-6 weeks after empirical antiparasitic treatment in travelers/migrants to determine treatment efficacy 3

The American Society of Hematology recommends a watch-and-wait approach with close follow-up for asymptomatic mild eosinophilia (<1.5 × 10⁹/L) without organ involvement, with monitoring of eosinophil counts every 3-6 months 3
Empirical antiparasitic treatment with albendazole and ivermectin is considered for mild eosinophilia in travelers/migrants (age >24 months) even if asymptomatic, to treat common helminths including Strongyloides 3