Associations between sarcoidosis, autoimmune diseases, and autoantibodies: a single-center retrospective study in China.

To describe the clinical manifestations, immunological features, and risk factors in patients with sarcoidosis complicated with autoimmune diseases (ADs) as well as determine the frequency of autoantibodies and possible correlation between autoantibodies and laboratory data. Patients with pathologically confirmed sarcoidosis at Beijing Chaoyang Hospital (China) between January 2017 and October 2020 were included. Age- and sex-matched patients who visited the rheumatology outpatient clinic without systemic or ADs were included as controls. Demographic, clinical, serological, and radiological data of sarcoidosis patients were recorded and analyzed. To exclude ADs, autoantibodies, such as antinuclear antibody, extractable nuclear antigen antibodies, and anti-cyclic citrullinated peptide antibody were assessed in controls. A total of 154 sarcoidosis patients (111 females; 72.1%) with a mean ± standard deviation age of 50.7 ± 10.3 years were included. Nineteen patients (12.3%) had ADs; Hashimoto's thyroiditis (n = 6) and Sjogren's syndrome (n = 4) were common. Age, globulin, immunoglobulin G, erythrocyte sedimentation rate (ESR), and C-reactive protein were significantly different between sarcoidosis patients with and without ADs. The ESR level might be a risk factor for sarcoidosis complicated with ADs (RR = 1.053; P = 0.018). Autoantibodies were detected in 29 patients (18.8%), and the frequency was significantly higher than that in controls (18.8% vs. 3%; P = 0.001). Sarcoidosis patients were more likely to have autoantibodies despite the absence of ADs (10.4% vs. 3%; P = 0.031). Age may be a risk factor for sarcoidosis patients presenting with autoantibodies (RR = 1.077; P = 0.042). An association was identified between ADs and sarcoidosis. The inflammatory indexes, such as ESR, IgG, and CRP, were significantly different between sarcoidosis patients with and without ADs. ESR might be a risk factor for the coexistence of ADs and sarcoidosis. Sarcoidosis patients were prone to being autoantibody-positive despite the absence of ADs, and age might be a risk factor for sarcoidosis presenting with autoantibodies.