Comorbid autoimmune diseases in patients with pemphigus: a nationwide case-control study in Taiwan.

Previous studies have proposed the association between pemphigus and several autoimmune diseases, but no large-scale study has been reported. To delineate the association between pemphigus and autoimmune diseases including psoriasis. A total of 1,998 patients with pemphigus and 7,992 control subjects were enrolled from the National Health Insurance Research Database in Taiwan from 1997 to 2010. The odds of comorbidities between these two groups were analysed by multivariate logistic regression. Compared with control subjects, patients with pemphigus were much more likely to have Sjögren's syndrome (odds ratio [OR]: 15.0; 95% confidence interval [CI]: 3.16-71.5), psoriasis (OR: 7.18; 95% CI: 5.55-9.29), systemic lupus erythematosus (OR: 4.46; 95% CI: 1.88-10.6), and alopecia areata (OR: 2.68; 95% CI: 1.26-5.67). According to gender-stratified analyses, however, the association between pemphigus and Sjögren's syndrome or alopecia areata was found to be significant only in the female patients. We confirm the association between pemphigus and some autoimmune diseases, including Sjögren's syndrome, systemic lupus erythematosus, and alopecia areata. In addition, we present the novel finding that patients with pemphigus have an increased risk of psoriasis.