A case-control study on autoimmune polyendocrine syndromes in patients with systemic lupus erythematosus

Objectives This study aimed to investigate the prevalence of Autoimmune Polyendocrine Syndromes (APS) in patients with Systemic Lupus Erythematosus (SLE) and to assess whether APS predicts higher disease activity or worse outcomes. Methods Clinical charts of 417 SLE patients, meeting SLICC 2012 and/or EULAR/ACR 2019 criteria, referring to our Centre between 2021 and 2023 were analysed. APS cases were identified using ORPHA definitions; 185 APS-free SLE patients, randomly enrolled, served as controls. Demographic, clinical and serological data were collected. Results Forty-seven of 417 (11%) SLE patients had another autoimmune disease affecting the glands that allows the diagnosis of APS: 39 were diagnosed with Hashimoto thyroiditis, 6 with Graves’ disease, and 3 with type 1 diabetes mellitus. Forty-five were affected by APS type 3, and 2 by APS type 4; no patients were diagnosed with APS 1 or 2. The comparison between APS+ and APS- patients revealed no significant differences in clinical or serological features. At the last evaluation, ∼80% of both groups’ patients were in clinical remission and approximately half of the patients remained on steroid therapy. APS+ patients had a slightly higher median damage index (SLICC-SDI), although this was not associated with increased disease activity. Conclusion The prevalence of APS among SLE patients is significantly higher than in the general population (11% vs 0,005%), confirming the association between autoimmune thyroiditis and SLE. However, APS+ patients do not appear to have a more aggressive disease or develop more complications.