Can Gastroesophageal Reflux Disease without Concomitant Eosinophilic Esophagitis Cause High-level Esophageal Eosinophilia?

There are no intraepithelial eosinophils present in the normal esophageal mucosa. It is well established that gastroesophageal reflux disease (GERD) and eosinophilic esophagitis (EoE) individually can result in esophageal eosinophilia and that the two disorders frequently coexist in the same patient. Nevertheless, the first step in the diagnostic algorithm for patients with esophageal symptoms associated with esophageal eosinophilia is to exclude non-EoE disorders that can cause esophageal eosinophilia, including GERD. While it is clear that GERD without EoE can cause low-level esophageal eosinophilia, it is less clear whether GERD alone can induce EoE-level esophageal eosinophilia (i.e., ≥15 eosinophils per high-power field). In this report, we have reviewed mechanisms by which reflux might induce eosinophilia in the esophagus and assessed studies suggesting that GERD alone can induce EoE-level esophageal eosinophilia. Studies on the latter issue have suffered from numerous shortcomings, including the use of outmoded or dubious methods for identifying GERD. Many of these studies were published prior to the realization that EoE can respond to proton pump inhibitor treatment. Our review of these studies suggests that GERD alone rarely, if ever, causes EoE-level eosinophilia (perhaps <1% of cases). For patients with definitive evidence of GERD associated with EoE-level esophageal eosinophilia but without endoscopic or clinical features of EoE, it is impossible to determine whether the eosinophilia is caused solely by GERD, by underlying but unrelated EoE that does not manifest typical features, or by EoE driven by GERD-induced defects, such as impaired esophageal barrier function. Until better diagnostic tests for EoE become available, this situation will remain a clinical conundrum.