Objective Multimorbidity is defined as the co-occurrence of at least two chronic conditions in the same individual. Multimorbidity can have an impact on patient´s quality of life, chronic disease outcome, treatment choices as well as premature death and an increased health care utilization. The aim of our study was to determine the prevalence of multimorbidity in Systemic Lupus Erythematosus (SLE) patients and its impact on disease activity.

Methods We conducted a cross-sectional single centre study including patients followed for diagnosis SLE according to EULAR/ACR 2019 Criteria for the Classification of Systemic Lupus Erythematosus and hospitalized or outpatient followed-up in our rheumatology department. Personal characteristics and disease manifestations were assessed for each patient. Excluding criteria contained cutaneous lupus and age over 60. Multimorbidity was defined as 2 or more comorbidities (excluding SLE). Substantial multimorbidity as the presence of 5 or more comorbidities. Comorbidities were evaluated using the Rheumatic Disease Comorbidity Index (RDCI) and the Multimorbidity index (MMI), disease activity by SLEDAI score.

Results A total of 123 SLE patients were included. 109 females (88,6%) and 14 males (11,4%) with a mean age of 42,12 (SD 10,08). The mean follow-up period was 13,34 (SD 9,13) years, only 7 patients (5,69%) were newly diagnosed. Multimorbidity was noted in 101 patients with SLE (82,4%). Substantial multimorbidity in 41 cases (33,3%). The mean comorbidity score measured by the RDCI was 1,5 (SD 1,3) and MMI 6,5. RDCI and MMI was positively correlated with SLEDAI (p=0,022, p=0,026). Both indexes were significantly higher in SLE patients older than 40years of age. Most frequent comorbidities according to RDCI were hypertension (35%), cardiovascular disease (28%) (except myocardial infarction – 1,6%), lung disease (17%) and depression (8,8%).

Conclusion Multimorbidity is an increasing problem especially in patients with chronic autoimmune disease. In this study, we confirmed the high prevalence of multimorbidity in SLE patients. Increased attention to this issue is necessary because of its impact on disease activity and patient prognosis.