While endoscopic changes were only subtle (slight mucosal irregularities such as fine nodules and rings), these patients showed T cell infiltration (CRTH2 negative, not fulfilling criteria for lymphocytic esophagitis) and moderate mast cell infiltration, and gene expression abnormalities similar to classical EoE (such as MUC4 and CDH26 genes), suggesting a uniform underlying pathogenesis [84]. The gene discussed is PTGDR2; the disease is eosinophilic esophagitis.