Eosinophilic esophagitis despite isolated IgG4 deficiency: The still unsolved conundrum of pathogenesis

In recent years, a strong association between IgG4 and eosinophilic esophagitis (EoE) has been recognized. Since 2014, when it was first suggested that IgG4 might be a relevant marker of EoE 1, several studies in both adult and pediatric patients have reported a significant increase in total and food-specific IgG4 levels in the esophageal biopsies and serum of EoE patients compared to controls. Additionally, there has been evidence of a reduction in esophageal and/or serum total and food-specific IgG4 levels following elimination diets or medical therapy 2.