Associations of pemphigus or pemphigoid with autoimmune disorders in US adult inpatients

Background: The associations and predictors of the gamut of autoimmune conditions in pemphigus and pemphigoid have been examined in few large-scale controlled studies. Objective: To examine associations of pemphigus or pemphigoid with autoimmune disorders and related outcomes in adults. Methods: Data from the 2002-2012 National Inpatient Sample were analyzed, including an similar to 20% sample of all US hospitalizations (n = 72,108,077 adults). Results: In multivariable logistic regression models, pemphigus (adjusted odds ratio 1.46, 95% confidence interval 1.30-1.63) and pemphigoid (adjusted odds ratio 1.35, 95% confidence interval 1.24-1.48) were associated with >= 1 autoimmune disorder. Pemphigus was associated with 9 of 29 and pemphigoid with 13 of 32 autoimmune disorders examined in bivariable models. Among pemphigus inpatients, unspecified autoimmune disease, vitiligo, eosinophilic esophagitis, and myasthenia gravis had the strongest effect sizes. Whereas, among pemphigoid inpatients, unspecified autoimmune disease, vitiligo, and chronic urticaria had the strongest effect sizes. There were significant differences of autoimmune comorbidities by age, sex, and race/ethnicity. The estimated excess annual costs of hospital care attributed to autoimmune disorders among inpatients with pemphigus was $2,286,588 and pemphigoid $4,301,681. Limitation: Lack of treatment history data. Conclusion: Inpatients with pemphigus or pemphigoid had increased odds of multiple cutaneous, extracutaneous, and systemic autoimmune disorders, which were associated with a considerable cost burden.