Eosinophilic esophagitis in Japan: Focus on response to acid suppressive therapy.

Eosinophilic esophagitis (EoE) is a chronic inflammatory condition characterized by esophageal dysfunction and dense eosinophilic infiltration of esophageal epithelium. According to clinical consensus and guidelines published in 2011, esophageal eosinophilia was classified into two entities based on response to proton pump inhibitor (PPI) administration: EoE and PPI-responsive esophageal eosinophilia (PPI-REE). We have performed a series of investigations to determine whether EoE is actually different from PPI-REE. Consistent with Western reports, more than half of our examined patients with symptomatic esophageal eosinophilia suggestive of EoE achieved histological remission with single PPI therapy. Furthermore, our comparisons of clinical, endoscopic, and histopathological findings between patients with EoE and those with PPI-REE revealed nearly no differences between them. We also compared gene expression profiles in mucosal biopsy specimens between those groups and found that microarray findings obtained from PPI-REE patients substantially overlapped with those from EoE patients, suggesting that both represent the same condition or are variations of a single disease. In addition, we have noted that more than half of EoE patients who show resistance to a PPI therapy respond to vonoprazan, a novel potassium-competitive acid blocker that has been shown to provide more potent and sustained suppression of gastric acid secretion than PPIs. Our results indicate that PPI-REE may constitute a subtype of EoE. Based on novel evidence including results obtained in our studies, the most recently updated guidelines have included responders to PPI therapy within the spectrum of EoE, abandoning the term PPI-REE.