Objectives: The aims of this study were to determine the outcomes and predictors of renal disease progression in Puerto Ricans with systemic lupus erythematosus (SLE) initially presenting mild renal involvement.
Methods: A retrospective cohort of 61 patients with SLE (per American College of Rheumatology classification) with mild renal involvement was studied. Mild renal disease was defined as glomerular filtration rate (GFR) of 90 mL/min or higher in the presence of proteinuria (>0.25 g/d, but <3.5 g/d), hematuria, and/or urinary cellular casts. Demographic parameters, clinical manifestations, serologic markers, comorbidities, pharmacologic treatments, disease activity, and damage accrual were determined at onset of renal disease. Factors associated with renal disease progression were evaluated using recurrent event survival analysis.
Results: Of 61 patients, 55 (90.2%) were women. The mean (SD) age at renal onset was 29 (11.2) years, and the mean (SD) follow-up period was 5.1 (3.4) years. Thirty-eight patients had a decline in GFR. Thirty-two had a mild decline (GFR = 60-89 mL/min), 5 developed moderate to severe renal insufficiency (GFR = 15-59 mL/min), and 1 evolved to end-stage renal disease (GFR < 15 mL/min). In the Cox model, low C4 levels and proteinuria greater than 0.5 g/d were associated with an earlier decline in GFR.
Conclusions: Most Puerto Rican patients with SLE initially presenting with mild renal involvement had a decrease in GFR after an average of 5 years of kidney disease, although most had a mild dysfunction. Low C4 levels and proteinuria were predictors of an earlier decline in GFR. We emphasize that awareness of these factors may contribute to early identification of individuals at risk for renal deterioration.