Eosinophil Associations in Health and Disease

Primary Associations of Eosinophilia

Allergic disorders account for approximately 80% of cases of eosinophilia, including asthma, food allergies, and atopic dermatitis 1
Parasitic infections, particularly intestinal helminths, are the second most common cause of eosinophilia 1
Eosinophilic esophagitis (EoE) is characterized by esophageal dysfunction and mucosal biopsy specimens containing ≥15 eosinophils per high-power field 2, 3
Hypereosinophilic syndromes (HES) are characterized by elevated eosinophils in peripheral blood (>1500 cells/μL) and organ damage due to eosinophilic infiltration 4
Autoimmune diseases including eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome) 4

Eosinophilic esophagitis (EoE) presents with symptoms of esophageal dysfunction (dysphagia, food impaction in adults; feeding problems, vomiting in children) 2, 5
EoE is characterized by ≥15 eosinophils per high-power field in esophageal biopsies and is often associated with other atopic conditions 2
50-80% of EoE patients have concurrent atopic conditions (allergic rhinitis, asthma, eczema) 2
Eosinophilic gastroenteritis can involve any part of the GI tract and may be associated with peripheral eosinophilia 4

Eosinophils are key players in allergic rhinitis, where they contribute to nasal mucosal inflammation 6
In asthma, eosinophils contribute to airway inflammation and remodeling 1
Nasal eosinophilia correlates with severity of perennial allergic rhinitis in children 6

Hypereosinophilic syndromes (HES) can affect multiple organs including the gastrointestinal tract, heart, skin, lungs, and nervous system 4
Up to 38% of HES patients have gastrointestinal symptoms 4
Persistent high-grade eosinophilia (>1.5 × 10⁹/L) can cause significant organ damage even without an identifiable cause 1
Eosinophilic granulomatosis with polyangiitis (EGPA) follows a three-stage pattern: prodromal (allergic rhinitis, asthma), eosinophilic (blood and tissue eosinophilia), and vasculitic (affecting multiple organ systems) 4

Eosinophils are associated with Th2 immune responses and produce cytokines including IL-4, IL-5, and IL-13 2
They contain cytotoxic granule proteins (eosinophil cationic protein, eosinophil-derived neurotoxin, peroxidase, major basic protein) that can damage tissues 2

Peripheral eosinophil counts are elevated in 10-50% of adults and 20-100% of children with eosinophilic esophagitis, though usually only modestly (2-fold) 2
Nasal smears for eosinophils can help diagnose allergic rhinitis and nonallergic rhinitis with eosinophilia 6
The absence of eosinophils with large numbers of neutrophils suggests infectious rhinitis or sinusitis 6
A detailed history of travel, exposures, medications, and symptoms is essential for evaluating eosinophilia 1

Topical glucocorticosteroids are effective in reducing esophageal eosinophil counts in EoE 5, 7
Dietary elimination strategies are effective in EoE, with moderate certainty for elemental diets 5, 7
Proton pump inhibitors may be effective in some patients with esophageal eosinophilia 5, 7
Dupilumab, a monoclonal antibody to IL-4 receptor alpha, is FDA-approved for EoE 4

Eosinophilia can be transient during the tissue migration phase of parasitic infections, when microscopic studies may be negative 1
Serological tests for helminths may not become positive until 4-12 weeks after infection and may exhibit cross-reactivity 1
Seasonal variations in symptoms and esophageal eosinophil levels have been reported in EoE patients 2
HES can often be distinguished from EoE by the presence of peripheral eosinophilia (>1500 cells/μL), which is rare in isolated EoE 4
The nasal eosinophil count correlates with the severity of perennial allergic rhinitis and may predict the progression to asthma 6