The beneficial effects of renin-angiotensin system inhibitors (RASI) on IgA nephropathy with tubulointerstitial lesions categorized by Oxford classification.

Background: Global sclerosis has been reported as the risk factor of IgAN. In Oxford classification, global sclerosis was correlated with tubulointerstitial (T) lesions. Therefore, in patients with T lesions, renin-angiotensin system inhibitors (RASI) might be effective by decreasing glomerular hyperfiltration and hypertension. However, these beneficial effects of RASI have not been reported.

Methods: In this retrospective cohort study, we divided 87 IgAN patients with T1/2 lesions into two groups: RASI group (n = 47, treated with RASI) and APA group (n = 40, treated with anti-platelet agents). We analyzed the background of each group, the serial changes of blood pressure and the amount of proteinuria (U-Prot), progression to end-stage renal disease, and the risk factors for progression.

Results: After propensity score matching, 22 cases from each group were selected, and clinical and histological characteristics were similar. Serial changes of blood pressure had been significantly decreased in RASI group (p = 0.0029), but not in the APA group. Proteinuria was tended to decrease in RASI group, though it was not significant (1.14-0.47 g/gCre) and it was similar in APA group (0.95-0.85 g/gCre). 20 year renal survival rate was 59.5% in RASI group, whereas 21.3% in APA group (p = 0.0119). In multivariate Cox regression analysis, RASI was an independent factor to prevent from progression to ESRD (HR 5.91, p = 0.0039).

Conclusion: RASI has shown a significant beneficial effect on histologically advanced IgAN patients with T lesions. These results are compatible with the previous studies that reported the beneficial effects of RASI on clinically advanced IgAN patients.