Prevalence of atopy, eosinophilia, and IgE elevation in IgG4‐related disease

IgG4‐related disease ( I g G 4‐ RD ) is a fibroinflammatory disorder that can affect virtually every organ system. T‐helper type 2 responses have been presumed to be pathogenic in this disease, and a high proportion of patients with I g G 4‐ RD are reported to have longstanding allergies, peripheral blood eosinophilia, and serum I g E elevation. It has therefore been proposed that allergic mechanisms drive I g G 4‐ RD . However, no epidemiological assessment of atopy, peripheral blood eosinophilia, and serum IgE concentrations has ever been undertaken in patients with I g G 4‐ RD . In this study, we evaluated these parameters in a large cohort of patients with I g G 4‐ RD in whom a wide range of organs were affected by disease. Our results demonstrate that the majority of patients with I g G 4‐ RD are nonatopic. Nevertheless, a subset of nonatopic subjects exhibit peripheral blood eosinophilia and elevated I g E , suggesting that processes inherent to IgG4‐ RD itself rather than atopy per se contribute to the eosinophilia and I g E elevation observed in the absence of atopy.