#4041 THE INTERSTITIAL TUBULAR INJURY IN THE COURSE OF LUPUS NEPHRITIS

Abstract

Abstract Background and Aims Tubulo-interstitial involvement in lupus nephritis (LN) refers to the presence of interstitial fibrosis and tubular atrophy (IFTA) in the renal biopsies of patients with lupus. The impact of these features on patient outcomes has not been fully established. The aim of this study was to determine the correlation between IFTA and patient outcomes in LN. Method A retrospective descriptive study was conducted on 160 patients with systemic lupus erythematosus who underwent renal biopsy between 2020 and 2022. Clinical and biological data, as well as histologic findings, were analyzed to determine the outcomes associated with IFTA in LN. Other causes of tubulointerstitial nephritis like drugs and toxins were excluded. Results The study population consisted of 148 females and 12 males, with a mean age of 37.2 years (ranging from 18 to 62 years) at the time of renal biopsy. Hematuria was observed in 62.5% of patients, nephrotic syndrome in 28.1%, hypertension in 24.3%, and renal failure in 17.5% with a mean proteinuria of 2.4±0.6 g/24 h. ANA was positive in a diffuse pattern in all cases, positive anti-ds-DNA,mean C3 was 29 (84-122 mg/dL), and mean C4 was 16.2 (20-40 mg/dl). Other serology C-ANCA and P-ANCA were all negative as well as negative HBV and HCV serology. However serology for Sjogren's syndrome was positive in 61 cases (41%). The histopathological study showed mild mononuclear and plasma cell infiltration of the interstitium, and tubular hyaline casts in 87% of cases. Examination of renal vessels was unremarkable in 94.5% of cases. IFTA was present in 72 patients (45%), with the most frequent glomerular involvement being LN class IV (55.5%) followed by LN class III (32.4%) with respectively (P = .09, P = .2)and was associated significantly with the anti-DNA antibody titer (P = .003). The severity of these lesions was found to be independently correlated with worsening of renal failure at 6 months follow-up (P = .02). Conclusion The findings of this study suggest that IFTA is a significant prognostic factor for the progression of renal failure in lupus nephritis, regardless of the class of the disease. The pathogenesis of tubulointerstitial lesions seems to be the result of circulating immune complexes specifically interacting with tubulointerstitial autoantigens.