Lifetime Allergy Symptoms in IgG4‐RelatedDisease: A Case–Control Study

The etiology of IgG4‐related disease (IgG4‐RD) is unknown, and there has been controversy over the significance of allergic conditions in IgG4‐RD. We examined the prevalence of lifetime allergy symptoms in IgG4‐RD and the association between these and IgG4‐RD. We identified IgG4‐RD patients and non‐IgG4‐RD controls without autoimmune conditions seen at a single center. IgG4‐RD patients were classified using the American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria. Allergy symptoms were ascertained by questionnaire. We assessed the association of IgG4‐RD features with allergy symptoms. We compared the proportion of cases and controls with allergy symptoms using conditional logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) after matching cases and controls 1:1 by age and sex. Lifetime allergy symptoms were reported by 165 (71%) of 231 IgG4‐RD patients. Aeroallergen symptoms were most commonly reported (n = 135, 58%), followed by skin allergy symptoms (n = 97, 42%) and food allergy symptoms (n = 47, 20%). IgG4‐RD cases with a history of allergy symptoms were more likely to have head and neck involvement (OR 2.0 [95% CI 1.1–3.6]) and peripheral eosinophilia (OR 3.3 [95% CI 1.2–9.0]) than those without allergy symptoms. The prevalence of any allergy symptoms was similar between cases and controls (OR 0.7 [95% CI 0.4–1.1]); this remained consistent after stratifying by head and neck involvement. Lifetime allergy symptoms are common in IgG4‐RD but are not reported more often in IgG4‐RD compared to non‐IgG4‐RD patients without autoimmune conditions. These findings suggest that allergies are not uniquely associated with the pathogenesis or presentation of IgG4‐RD.