The association between sarcoidosis and autoimmune comorbidities has been reported, however, it has seldom been confirmed by a large nationwide study. Our study aimed to clarify the association between sarcoidosis and autoimmune comorbidities in the Taiwanese. A total of 1237 patients with sarcoidosis and 4948 age- and sex-matched control subjects were selected from the National Health Insurance Research Database of Taiwan from 1997 to 2010. Multiple logistic regressions were performed to calculate the odds of comorbidities between the two groups. The prevalence of sarcoidosis was 2.17/100 000 individuals in Taiwan. Sarcoidosis patients tended to run a higher risk of autoimmune comorbidities than the control group (17.6% vs 9.4%, P < 0.05). Autoimmune thyroid disease (adjusted odd ratio [aOR], 1.32; 95% confidence interval [CI], 1.05-1.64), Sjögren's syndrome (aOR, 11.6; 95% CI, 4.36-31.0) and ankylosing spondylitis (aOR, 3.80; 95% CI, 2.42-5.97) were significantly associated with sarcoidosis. The sex-stratified analyses were carried out to demonstrate a significant association of sarcoidosis with ankylosing spondylitis in both sexes, but with autoimmune thyroid disease in male patients and with Sjögren's syndrome female patients, respectively. Besides, the diagnosis of the autoimmune comorbidities strongly associated with sarcoidosis tended to be established after that of sarcoidosis. This study demonstrated that patients with sarcoidosis tended to have autoimmune thyroid disease, Sjögren's syndrome and ankylosing spondylitis, and the diagnosis of sarcoidosis usually preceded that of associated comorbidities. Clinicians should be alert to autoimmune comorbidities in patients with sarcoidosis.

Lichen planus is associated with various autoimmune diseases. Further study is required to elucidate the possible underlying mechanisms and roles of autoimmunity in the aetiology of LP.

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