A 42-year-old male presents with progressive dysphagia to solids over 6 months and a recent episode of food impaction requiring emergent endoscopic removal. Upper endoscopy reveals the findings marked **A** in the diagram: concentric rings with linear furrows and white exudates. Esophageal biopsies from proximal and distal esophagus show 28 eosinophils per high-power field. Which of the following best describes the pathophysiologic mechanism underlying this patient's condition?
A. Th1-mediated autoimmune destruction of esophageal smooth muscle leading to achalasia-like dysmotility
B. Bacterial overgrowth causing secondary eosinophilic infiltration and stricture formation
C. Gastroesophageal reflux-induced peptic injury with reactive eosinophilic response limited to the distal esophagus
D. Th2-mediated allergic inflammation triggered by food antigens, with key cytokines IL-5 and IL-13 recruiting eosinophils via eotaxin-3/CCL26 in genetically susceptible individuals
Explanation
Why option 1 is correct
The endoscopic findings marked A (concentric rings, linear furrows, white exudates) combined with ≥15 eosinophils/HPF on biopsy are pathognomonic for eosinophilic esophagitis (EoE). The AGA-JTF EoE Guidelines 2020 and AGREE consensus 2018 define EoE as a chronic, immune/antigen-mediated esophageal disease. The pathogenesis is driven by Th2-mediated allergic inflammation triggered by food antigens (milk, wheat, egg, soy, peanut/tree nut, fish/shellfish) and aeroallergens in genetically susceptible individuals. The key cytokines IL-5 and IL-13 recruit eosinophils via eotaxin-3/CCL26, establishing the characteristic eosinophil-predominant inflammation. This mechanism is distinct from GERD and explains the clinical presentation of food impaction and dysphagia.
Why each distractor is wrong
Option 2 (Th1-mediated autoimmune destruction): EoE is fundamentally a Th2-mediated allergic disease, not a Th1-mediated autoimmune condition. Th1 responses are associated with other esophageal conditions (e.g., some infectious esophagitis), not EoE. The histology shows eosinophilic infiltration, not smooth muscle destruction.
Option 3 (Bacterial overgrowth): EoE is an immune/antigen-mediated disease, not an infectious process. Bacterial overgrowth does not produce the characteristic concentric rings and white exudates seen in EoE, nor does it drive the specific Th2 cytokine cascade.
Option 4 (GERD-induced peptic injury): While GERD can cause esophageal eosinophilia (formerly requiring PPI trial to exclude), the 2018 AGREE consensus clarified that PPI-responsive disease is part of the EoE spectrum. However, this patient's biopsies show ≥15 EOS/HPF with the classic endoscopic triad (rings, furrows, exudates), which is diagnostic of EoE itself. GERD-induced eosinophilia is typically distal and does not produce the "trachealization" pattern seen here.
High-YieldNEET PG
EoE is a Th2-mediated allergic disease (not autoimmune, not infectious, not purely GERD); IL-5 and IL-13 via eotaxin-3/CCL26 are the key pathogenic cytokines driving eosinophil recruitment.
AGA-JTF EoE Guidelines 2020; AGREE consensus 2018
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