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The purpose of this study is to discuss the clinical, endoscopic and histologic features, pathogenesis and disease mechanisms of proton pump inhibitor (PPI)-responsive oesophageal eosinophilia (PPI-REE), and to highlight similarities and differences with eosinophilic oesophagitis (EoE).PPI-REE is a condition in which patients have clinical and histologic findings similar to EoE, but achieve complete remission with PPI treatment. More than one-third of patients who have oesophageal symptoms associated with oesophageal eosinophilia respond to PPI treatment. Emerging data elucidating the pathogenesis of PPI-REE have shown that Th2-related inflammatory factors such as interleukin (IL)-13, IL-5, eotaxin-3 and major basic protein (MBP) are elevated in PPI-REE, similar to EoE. PPI-REE also shares a genetic expression signature with EoE that reverses with PPI treatment. Mechanisms proposed to explain the PPI response include an acid-independent, anti-inflammatory action of PPIs and PPI-induced restoration of oesophageal barrier function.Multiple features of PPI-REE overlap extensively with EoE. This raises the question of whether PPI-REE is merely a subtype of EoE rather than an independent condition. This similarity may have future implications for algorithms informing evaluation and treatment of oesophageal eosinophilia.