Patients with systemic lupus erythematosus who are underweight have distinct disease characteristics

<bold>Objective: </bold>This study aimed to detail the disease characteristics of systemic lupus erythematosus (SLE) in individuals who are underweight and assess whether underweight status is associated with SLE disease activity.<bold>Methods: </bold>This was a retrospective cohort study involving 218 patients newly diagnosed with SLE. Patients were categorized as underweight (body mass index [BMI] <18.5 kg/m(2)) or not underweight (BMI >= 18.5 kg/m(2)). We reviewed disease characteristics including the SLE Disease Activity Index 2000 (SLEDAI-2K) at diagnosis. High disease activity was defined as SLEDAI-2K >= 10. Disease characteristics were compared between those who were underweight and not underweight. We used multivariable logistic regression analysis to determine whether underweight status is associated with high disease activity.<bold>Results: </bold>Out of the 218 patients, 35 (16.1%) were underweight and 183 (83.9%) were not. Underweight patients had less renal involvement (5.7% vs 20.2%, p = .040), lower C-reactive protein levels (1.0 [0.3-2.3] mg/L vs 1.2 [0.8-5.0] mg/L, p = .028), and lower SLEDAI-2K scores (6.7 +/- 4.6 vs 9.1 +/- 5.7, p = .009), and were less likely to be at high disease activity status (22.9% vs 42.6%, p = .028), compared with those who were not underweight. Following adjustment for multiple covariates, being underweight was inversely associated with high disease activity status (adjusted odds ratio = 0.38, 95% confidence interval = 0.16 to 0.92, p = .031).<bold>Conclusion: </bold>Patients with SLE who were underweight showed less renal involvement and lower SLEDAI-2K scores compared with those who were not underweight. Moreover, those with SLE who were underweight had a 60% lower risk of exhibiting high disease activity.