Does esophageal eosinophilia cause hypoeosinophilia (low eosinophil count)?

Esophageal Eosinophilia Does Not Cause Low Peripheral Eosinophil Counts

Esophageal eosinophilia does not cause hypoeosinophilia (low peripheral eosinophil counts); in fact, patients with eosinophilic esophagitis (EoE) often have normal or elevated peripheral eosinophil counts. 1

Relationship Between Esophageal and Peripheral Eosinophils

Peripheral Eosinophil Patterns in EoE

• Studies show that 10-50% of adults and 20-100% of children with EoE have elevated peripheral eosinophil counts, typically modestly elevated (about 2-fold) 1
• No evidence in the literature suggests that esophageal eosinophilia depletes circulating eosinophils or causes hypoeosinophilia
• Peripheral eosinophilia in EoE patients is likely due to concurrent allergic conditions that are common in these patients 1

Clinical Correlation

• In some studies, persistent blood eosinophilia correlated with persistent dysphagia 1
• The degree of elevation of serum eosinophils has been shown to correlate with the severity of EoE in some patients 1
• Treatment of EoE with corticosteroids or fluticasone has been shown to decrease blood eosinophil counts in most patients 1

Diagnostic Considerations

Peripheral Eosinophil Count as a Biomarker

• While peripheral eosinophil counts may provide supportive evidence for EoE and potentially correlate with tissue involvement, they are not diagnostic on their own 1
• The sensitivity, specificity, and predictive values of peripheral eosinophil counts for EoE diagnosis are limited
• When combined with other markers like eosinophil-derived neurotoxin (EDN), peripheral eosinophil counts can improve diagnostic accuracy (sensitivity 63%, specificity 92%, positive predictive value 83%, negative predictive value 79%) 1

Histological Diagnosis

• The diagnosis of EoE requires ≥15 eosinophils per high-power field (or ≥15 eosinophils/0.3 mm² or >60 eosinophils/mm²) on esophageal biopsy 1
• Multiple biopsy specimens from different anatomical sites within the esophagus should be obtained for accurate diagnosis 1
• Other histological features supporting EoE diagnosis include basal cell hyperplasia, eosinophil microabscesses, eosinophil layering, eosinophil degranulation, and subepithelial sclerosis 1

Pathophysiological Considerations

• EoE is an immune/antigen-driven chronic inflammatory condition with a Th2-predominant immune response 1
• The disease involves elevated levels of eosinophil-active Th2 cytokines (IL-4, IL-5, IL-13) and mast cells in the esophagus 1
• Eosinophils are actively recruited to the esophageal mucosa through specific chemokines like CCL26 (eotaxin-3) 1
• This recruitment represents an active inflammatory process rather than a sequestration that would deplete circulating eosinophils

Clinical Implications

• When evaluating patients with suspected EoE, clinicians should not expect to find low peripheral eosinophil counts
• Normal or elevated peripheral eosinophil counts may actually support the diagnosis of EoE, particularly in patients with appropriate symptoms and endoscopic findings
• Monitoring peripheral eosinophil counts may be helpful in assessing treatment response, but should not be used as the sole marker of disease activity 1

In summary, esophageal eosinophilia in EoE is associated with normal or elevated peripheral eosinophil counts rather than hypoeosinophilia, reflecting the systemic allergic nature of the disease rather than a compartmentalization that depletes circulating eosinophils.