Introduction:
Systemic lupus erythematosus (SLE) is a complex autoimmune disease with clinical and laboratory characteristics influenced by the age of onset. Despite its significance, data on late-onset SLE (Lo-SLE) compared to early-onset SLE (Eo-SLE) remain limited, particularly in the Polish population. We investigated differences between Lo-SLE and Eo-SLE patients (using 50 years as a cutoff), aiming to improve the diagnosis and management of SLE patients across different age groups.

Material and methods:
We conducted a retrospective analysis of medical records from all SLE patients treated at the University Hospital in Krakow, Poland, from 2012 to 2022. All included patients met the 2019 European Alliance of Associations for Rheumatology and American College of Rheumatology classification criteria for SLE.

Results:
We analyzed 710 patients with Eo-SLE (77.9%) and 201 patients with Lo-SLE (22.1%). Compared to the Eo-SLE group, the Lo-SLE group exhibited shorter disease duration (p < 0.001), a higher mortality rate (p < 0.001), and distinct clinical features: less involvement of the central nervous system (n = 5, 2.5% vs. n = 51, 7.23%, p = 0.014) and kidney (n = 49, 24.38% vs. n = 294, 41.41%, p < 0.001), more frequent interstitial lung disease (n = 19, 9.45% vs. n = 27, 3.84%, p = 0.001), and a higher prevalence of cardiovascular, metabolic, and neoplastic comorbidities (p < 0.05, for all). Autoantibody profiles also differed: in Lo-SLE compared to Eo-SLE patients, anti-SSB were more common, while anti-histone, anti-nucleosome, anti-RNP, and anti-dsDNA antibodies were less pre­valent. Late-onset SLE patients received immunosuppressive treatment less often than Eo-SLE patients.

Conclusions:
Late-onset SLE patients exhibit different disease manifestations but with a higher prevalence of interstitial lung disease, internal medicine comorbidities, malignancies, and cardiovascular events compared to Eo-SLE. Our findings highlight the need for tailored management stra­tegies in elderly SLE patients.