Interstitial inflammation and long-term renal outcomes in lupus nephritis

Introduction The International Society of Nephrology/Renal Pathology Society (ISN/RPS) pathological classification criteria of lupus nephritis are limited to glomerular injury. Although the tubulointerstitium is commonly involved, the importance of such involvement is not well defined. The major objective of this study was to evaluate the association of interstitial inflammation with the long-term outcomes of patients with lupus nephritis. Patients and methods A total of 73 patients who were diagnosed with lupus nephritis between 1996 and 2012 were analyzed. The follow-up data were obtained, and the analysis was conducted to determine the effect of interstitial inflammation on the rate of the doubling of serum creatinine or end-stage renal disease (ESRD) in patients with lupus nephritis. Of the patients included in the cohort, 63 underwent a second biopsy. Results The degree of interstitial inflammation was positively correlated with the serum creatinine level at the time of biopsy (p=0.005) but not at the end of the follow-up period (p=0.9). The complements level, anti-dsDNA, ANA, and proteinuria were not related to the degree of interstitial inflammation. There was no relationship between the probability of remission and the severity of interstitial infiltrate. The rate of no remission was 40% among those without interstitial infiltrate, 34.6% in those with mild infiltrate and 23.5% among those with moderate-to-severe infiltrate (p=0.6). There was no relationship between interstitial inflammation at the baseline biopsy and worsening of renal function (p=0.17). There was a strong relationship between interstitial inflammation at the repeat biopsy and renal survival (p=0.005). The recovery of interstitial inflammation in lupus nephritis correlated with a favorable outcome in the patients with interstitial inflammation at baseline that had resolved at the repeated biopsy (p=0.047). Conclusion The persistence of interstitial inflammation is associated with poor renal outcome among patients with lupus nephritis. A comprehensive histological assessment of inflammation in lupus nephritis including interstitial inflammation may provide better prognostic information.