OBJECTIVES: To describe the hospital stays of patients with systemic lupus erythematosus (SLE) in Belgium during one calendar year. METHODS: All adult patients having ≥1 stay with a primary or secondary diagnosis of SLE (ICD-9-CM code 710.0) in 2013 were retrieved from the longitudinal IMS Hospital Disease Database (HDD; capturing 24% of Belgian hospital beds). All stays generated by these patients during the year were retrieved with their characteristics (admission type, associated diagnoses, in-hospital mortality, length of stay, drugs, procedures, costs) and descriptive statistics were derived (mean +/- standard deviation or [interquartile range]). Correlation coefficients (Pearson, Spearman) were calculated between age, number of stays/patient, total length of stay/patient, annual cost/patient and the number of organ systems involved (estimated per patient, based on the ICD-9-CM codes of associated diagnoses, further classified into SLE-specific organ systems). RESULTS: In 2013, 434 adult SLE patients were identified (82.0% female; mean age 54.8 +/- 17.0 years; mean 3.0 [2-4] organ systems involved distributed as follows: Musculoskeletal 97.9%, Circulatory/respiratory 54.4%, Mental/Nervous system 38.8%, Digestive 31.8%, Renal 29.0%, Haematologic 25.0%, Skin/subcutaneous tissue 15.4%, Ophthalmic 6.1%. The mean annual hospitalization cost/patient was €8,741 [1,715-9,533]). These patients generated 939 stays (2.2 [1-2] stays/patient; 29.7% unplanned admissions; 56.4% full hospitalizations with mean length of stay 8.4 days [2-9]). The in-hospital mortality was 2.2% and the mean total cost/stay was €4,069 [366-4,202]). The number of organ systems involved was significantly (p<0.001) correlated to age (Pearson/Spearman: 0.40/0.38), number of stays/patient (0.21/0.26), total length of stay (0.57/0.59) and annual cost/patient (0.53/0.55). CONCLUSIONS: The analysis of real-world hospitalization data showed how the burden and complexity of SLE management increases as the organ systems involvements accrue. Extrapolating the HDD data to the total Belgian population, about 1,800 SLE patients might require hospital treatments every year, representing a substantial burden for patients and society.