Role of tubulointerstitial lesions in predicting renal outcome among pediatric onset lupus nephritis – A retrospective cohort study

Background: Raising evidence suggested a prognostic utility of tubulointerstitial lesions in lupus nephritis (LN). The exact prevalence of tubulointerstitial abnormalities and its predictive value among pediatric onset systemic lupus erythematous (pSLE) cases, however, remained unknown. Methods: Sixty-seven pSLE subjects diagnosed with LN with initial renal samples available were enrolled and followed for an average of 6.49 ± 3.06 years. Renal histology was evaluated according to the International Society of Nephrology/Renal Pathology Society classification, National Institute of Health classification and tubulointerstitial activity index (TIAI). Results: Tubulointerstitial injuries were observed in 38.81% of all LN cases, including 13.33% with non-proliferative lupus nephritis (nPLN) and 46.15% of with proliferative lupus nephritis (PLN). Tubulointerstitial injuries occurred solitarily in cases with nPLN(13.33%), but always associated glomerular changes and significantly impacted renal survival (p = 0.032) among those with PLN. TIAI associated glomerular abnormalities (p = 0.031) but did not correlate renal performance or subsequent outcome (p = 0.445). Among the chronicity index, it was the chronic tubulointerstitial lesions that provided prognostic information (p = 0.012). None of the individual tubulointerstitial factors, however, reached statistical significance in end-stage renal disease prediction. Finally, considering tubulointerstitial injuries in PLN further discriminated subsequent renal outcome (p = 0.006). Conclusion: Tubulointerstitial abnormalities were found in nearly one-third of all pediatric LN cases. With its importance in early identifying those at risk of renal failure, histologic classification considering tubulointerstitial lesions may potentially assist outcome prediction.