Interaction with
gastroesophageal reflux disease (
GERD) has been a fundamental consideration in
eosinophilic esophagitis (EoE) since the initial reports of this emerging entity. While studies from the '80s identified the presence of esophageal
eosinophilia as being a histologic marker for the diagnosis of
GERD, studies in the '90s demonstrated that high levels of esophageal
eosinophilia were characteristic for a novel immune/
antigen-mediated
esophageal disease, EoE, that was seemingly quite distinct from
GERD. However, several recent studies have demonstrated the effectiveness of
proton pump inhibition (PPI) in reducing symptoms and histopathology in a subset of patients with esophageal
eosinophilia and suspected EoE, leading to the terminology "PPI responsive esophageal
eosinophilia." It remains uncertain as to whether these patients have EoE,
GERD, or a PPI responsive esophageal inflammatory condition that is distinct from either
GERD or EoE. Emerging translational research has evidenced mechanisms by which PPI response in patients with esophageal
eosinophilia may be a consequence of PPI effects on the immune pathogenesis of EoE. Therefore, a symptom and histologic response to PPI in patients with esophageal
eosinophilia does not necessarily "rule in"
GERD. Until further studies better define the pathogenesis of PPI responsive esophageal
eosinophilia, a trial of PPI
therapy remains an important prerequisite to the diagnosis EoE. Following this diagnostic approach allows for the clinical application of available evidence that is derived from research trials in EoE that exclude PPI responsive
eosinophilia.