Idiopathic nephrotic syndrome is a common nephropathy in children basically treated with corticosteroids and, in some cases, with cyclosporin A. There are concerns that proteinuria itself and cyclosporin A could cause renal fibrosis via activation of transforming growth factor beta (TGF-β), which may stimulate deposition of collagen type III, synthesised as procollagen III amino terminal propeptide (PIIINP). The aim of this study was to assess urinary TGF-β and PIIINP to creatinine (Cr) ratio as markers of renal fibrosis in children with idiopathic nephrotic syndrome put on corticosteroid and cyclosporin A treatment. Materials and methods: The study comprised 20 children with idiopathic nephrotic syndrome in remission on prednisone, aged 6.87 years [interquartile range (IQR): 6.37]; 21 children with idiopathic nephrotic syndrome in remission on cyclosporin A, aged 9.66 years (IQR: 5.0); and 21 healthy subjects, aged 7.16 years (IQR: 9.0). First morning urinary PIIINP/Cr and TGF-β/Cr were obtained and compared with Mann–Whitney U test, with the level of significance at p ≤ 0.05. Results: PIIINP/Cr ratio was significantly elevated in the cyclosporin A group [3.44 (2.5) vs. 1.12 (0.96) μg/mmol], p = 0.000, as well as in the prednisone group when compared to controls [1.33 (1.58) vs. 1.12 (0.96) μg/mmol], p = 0.042. The TGF-β/Cr ratio was significantly higher only in the cyclosporin A group when compared to controls [4.03 (3.25) vs. 2.33 (1.62) μg/mmol], p = 0.004. Conclusions: Increased urinary PIIINP/Cr ratio in children with idiopathic nephrotic syndrome either on steroid or on cyclosporin A therapy may suggest that renal fibrosis is a process generally involved in idiopathic nephrotic syndrome. Elevated urinary TGF-β/Cr and PIIINP/Cr ratios in patients with idiopathic nephrotic syndrome on cyclosporin A may reflect nephrotoxicity of this drug.

idiopathic nephrotic syndrome, interstitial fibrosis, cyclosporine A, transforming growth factor beta, procollagen type III aminoterminal propeptide