Association between bullous pemphigoid and atopic dermatitis: a population-based case-control study in Taiwan

Although bullous pemphigoid (BP) and atopic dermatitis (AD) share pathogenic mechanisms, their relationship remains controversial. Therefore, we conducted a population-based case-control study to investigate the association between BP and AD in Taiwan. Based on the Taiwan National Health Insurance Research Database, 9344 patients with BP and 18,688 age- and sex-matched controls were enrolled between 2000 and 2013. Furthermore, the study included 7,196 BP patients and 14,392 controls, matched for age, sex, and propensity score of comorbidities, with a case to controls ratio of 1:2. Logistic regression analysis was performed to examine the association between AD and BP. In the age- and sex-matched cohorts, AD (odds ratio [OR], 1.71; 95% confidence interval [CI], 1.50-1.95) was independently associated with BP. In the age, sex, and comorbidities-matched cohorts, AD (OR 1.76, 95% CI 1.55-2.00) remained a significant risk factor for BP. Other significant risk factors included psoriasis, hypertension, diabetes mellitus, chronic kidney disease, chronic obstructive pulmonary disease, neuropsychiatric diseases, and autoimmune connective tissue disease. Limitations of this study include the lack of information on disease severity and phenotypes of BP and misclassification of diseases as potential sources of bias. In conclusion, AD increased the risk of developing BP by 76%, and this association was independent of many BP comorbidities. Further studies are warranted to investigate the clinical and pathophysiological relevance of factors contributing to BP and AD.