Background: Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease predominantly affecting young individuals; however, its late-onset manifestation poses distinct clinical and diagnostic challenges. Methods: This report describes the case of a 93-year-old patient who presented in the Emergency Department with exertional dyspnea, lower limb edema, fatiguability, diffuse abdominal pain, predominantly in the hypogastric region, and loss of appetite. Results: Based on the clinical examination, laboratory tests, and imagistic investigations, we excluded the most common etiologies of edema (decompensated chronic heart failure, glomerular nephropathy/chronic kidney disease, decompensated vascular cirrhosis, hypothyroidism, and hypoproteinemia). Further diagnostic evaluation revealed elevated levels of anti-nuclear antibodies and anti-dsDNA antibodies, along with reduced complement levels, indicating active SLE as the underlying cause of the patient’s edema. During hospitalization, the patient received corticosteroid therapy and, after discharge, was referred to the Rheumatology Department for further treatment. Conclusions: In elderly patients, late-onset SLE exhibits distinct clinical manifestations compared to its early-onset counterpart, likely due to age-related alterations in immune system function.