Clinical, laboratory, and histopathological characteristics of pediatric lupus nephritis: a retrospective study in a national referral center in Mexico.

Background: Pediatric lupus nephritis (LN) remains a major cause of morbidity and mortality, yet data from Latin American populations are limited. This study aimed to describe the clinical, laboratory, and histopathological characteristics of pediatric LN and identify prognostic factors associated with renal replacement therapy (RRT). Methods: We conducted a retrospective cross-sectional study including patients <18 years of age with LN diagnosed between 2020 and 2024 at a national referral center in Mexico. Demographic, clinical, immunological, histopathological, and therapeutic variables at diagnosis were analyzed. Multivariable logistic regression was performed to identify predictors of RRT. Results: Eighty patients were included (83% female; mean age 15.1 ± 2.8 years). Median proteinuria was 41 mg/m²/h; hematuria and leukocyturia were present in 46% and 26% of patients, respectively. All patients were ANA positive, with frequent hypocomplementemia and elevated anti-double-stranded DNA titers. Among biopsied patients, class IV was the most common histological subtype (60%). Proliferative forms were associated with reduced glomerular filtration rate (<90 mL/min/1.73 m²; Conclusions: This study represents one of the largest pediatric LN cohorts reported from Mexico. Proliferative forms were associated with greater inflammatory activity and impaired renal function at diagnosis. Hypoalbuminemia emerged as a simple and accessible biomarker for early risk stratification of severe renal outcomes.