Hypereosinophilia Causes and Diagnostic Considerations

Primary and Secondary Causes

Allergic and atopic disorders are the most common cause of hypereosinophilia, accounting for approximately 80% of secondary reactive cases, followed by parasitic infections as the second most frequent etiology 1, 2
The American College of Cardiology is not mentioned in this context, however, the most common parasitic cause is Strongyloides stercoralis, particularly important because it can persist lifelong and cause fatal hyperinfection syndrome in immunocompromised patients 3, 2
Hookworm (Ancylostoma duodenale, Necator americanus) is another common parasitic cause of hypereosinophilia 1, 2
Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase fusion genes are a primary cause of hypereosinophilia 3, 1

Geographic and exposure history is crucial in diagnosing hypereosinophilia, as helminth infections are the most common identifiable cause in returning travelers and migrants (19-80% diagnosis rate) 2
The National Comprehensive Cancer Network recommends considering the temporal patterns of serological tests for helminths, which may not become positive until 4-12 weeks after infection 1, 2
Patients with eosinophilia and evidence of end-organ damage need urgent medical assessment, according to the Praxis Medical Insights guidelines 2

Persistent high-grade eosinophilia (>1.5 × 10⁹/L) can cause significant organ damage, affecting the heart, lungs, gastrointestinal tract, nervous system, and skin 1, 2, 3
The Journal of the National Comprehensive Cancer Network notes that organ damage can occur even without an identifiable cause of hypereosinophilia 3, 2