Nonlupus Nephritides in Patients with Systemic Lupus Erythematosus

Background: Few reports have been published regarding the incidence of non-lupus nephritides in patients with an established systemic lupus erythematosus (SLE) diagnosis Methods: Cross-sectional trial including all kidney biopsies performed in our institution in patients with SLE diagnosis from December 2014 to March 2024. Results: We included 45 biopsies; 38 patients were women (82%) with an average age of 38 years. The most common biopsy indications were: subnephrotic range proteinuria (33%), rapidity progressive renal failure (24%), and nephrotic syndrome (22%). At the time of biopsy, 44% of patients had an estimated glomerular filtration rate <60 ml/min/1.73m2, while 44% had no functional deterioration, and only 2% required renal support therapy at this time. The most common histopathological diagnosis among our sample was class III + V lupus nephritis (20%), followed by class IV and V (both 16%). When analyzing non-lupus nephritides, the most represented were focal segmental glomerulosclerosis (4%) and minimal changes disease (4%) followed by membranoproliferative pattern and IgA nephropathy representing 2% of the sample. Conclusion: In our sample, 10% of patients presented with non-lupus nephritides even though they had an established SLE diagnosis which exemplifies the importance of histopathological diagnosis at any sign of renal activity since a different cause could be responsible and may warrant a different treatment.