Prediction of Systemic Lupus Erythematosus Exacerbation in Patients with Clinical and Subclinical Musculoskeletal Inflammation.

Background/Objectives: Systemic lupus erythematosus (SLE) is an autoimmune disease affecting multiple organ systems, characterized by remissions and relapses. Musculoskeletal involvement occurs in up to 95% of patients and may present as the initial symptom in 50%. Such involvement is often subclinical, without obvious joint or tendon inflammation. Musculoskeletal ultrasound (US) has proven valuable for detecting pathological changes in joints and periarticular structures, including in SLE patients, and early detection, particularly in subclinical stages, supports optimal therapy, monitoring, and improved prognosis. This study aimed to determine the frequency of new clinical manifestations in patients with previously confirmed clinical and subclinical musculoskeletal inflammation after 2 and 5 years, and to evaluate associations with sex, age, BMI, smoking status, ESR, CRP, SLEDAI-2K, complement components C3 and C4, anti-dsDNA antibodies concentrations, and prior treatment. Methods: The study included 34 SLE patients with clinical and 22 with subclinical musculoskeletal inflammation, confirmed at baseline by history, examination, and US. Follow-up at 2 and 5 years recorded new clinical manifestations. Correlations with patient characteristics were assessed to identify predictors. Results: New clinical manifestations occurred in 34% of patients at 2 years and 48% at 5 years, most commonly cutaneous, musculoskeletal, and hematological. Summary analysis identified female sex, lower BMI, and lower baseline SLEDAI-2K scores as the strongest predictors. In the subclinical group, female sex, smoking, and lower SLEDAI-2K scores were predictive, while in the clinical group, female sex, lower SLEDAI-2K scores, lower ESR, and higher anti-ds DNA levels were associated with new manifestations. Conclusions: Female sex, lower BMI, and lower baseline SLEDAI-2K scores are key predictors of new clinical manifestations in SLE patients, highlighting the importance of early detection and individualized monitoring, particularly in patients with subclinical musculoskeletal inflammation.