Abstract: Background A few cases of childhood primary nephrotic syndrome showed steroid-resistant nephrotic syndrome (SRNS) which was difficult to treat. For these cases of SRNS, after excluding genetic factors other agents were added such as calcineurin inhibitor and mycophenolate mofetil. However, there were no regular principles or unified therapeutic schedules. Objective To observe the therapeutic effects and safety of steroid combined with calcineurin inhibitors and mycophenolate mofetil on pediatric cases of steroid-resistant nephrotic syndrome. Design Retrospective non-randomized controlled study. Methods Data were collected from children with steroid-resistant nephrotic syndrome treated in the department of pediatrics of Peking University First Hospital from January 2014 to December 2020. After excluding genetic factors, they were divided into four groups as A (steroid + calcineurin inhibitor + mycophenolate mofetil, added sequentially), B (if steroid combined calcineurin inhibitor for over 3 months is ineffective, it will be replaced by steroid combined with mycophenolate mofetil for over 3 months. If there is still no effect, the triple therapy of steroid, calcineurin inhibitor and mycophenolate mofetil will be used.), C (calcineurin inhibitor + mycophenolate mofetil, withdrawal of steroid because of glucocorticoid diabetes or glaucoma) and D (steroid + calcineurin inhibitor + rituximab). Main observation parameters The time of urine protein changed negative, the time percentage of urine protein remained negative and average numbers of relapse. Results There were 39 pediatric cases of steroid-resistant nephrotic syndrome in this study, including 16, 8, 3 and 12 cases in group A, B, C and D, respectively. The urine protein negative rates of group A, B, C and D were 75.0% (12/16), 75.0% (6/8), 100% (3/3) and 75.0% (9/12), respectively. There was no difference on urine protein negative rate between four groups (P>0.05). However, the average time of urine protein conversed to negative was much less while the percentage of urine protein conversed to negative was much higher in groups A and D as compared to group B and C (P<0.05). There was no significant difference in the average time of urine protein conversed to negative and the percentage of urine protein conversed to negative between group A and group D (P>0.05). Conclusion Steroid combined with calcineurin inhibitors and mycophenolate mofetil showed better effects on some idiopathic steroid-resistant nephrotic syndrome in children.

Key words: Nephrotic syndrome, Steroid-resistant, Calcineurin inhibitors, Mycophenolate mofetil