IGHE and allergic disease: As a major mediator of clinical allergy, an elevated serum IgE level was detected in 35.0% to 88.9% of IgG4-RD patients.[32,33] A large retrospective cohort study that investigated serum IgE levels in the clinical features and outcomes of IgG4-RD revealed that IgG4-RD patients with high serum IgE levels at baseline were more likely to have higher disease activity, and baseline high IgE levels were associated with disease relapse.[34] Our patient’s medical history indicated that environmental exposures might have been involved in the development of IgG-RD.