Anti-nephrin antibodies in idiopathic nephrotic syndrome in Japanese children

Background Many patients with childhood idiopathic nephrotic syndrome are steroid-sensitive. Several genome-wide association studies have suggested a polygenic contribution, particularly in the HLA DR/DQ region and a locus including nephrin, but the etiology remains unclear. Anti-nephrin antibodies have recently been reported in both adults and children with biopsy proven minimal change disease (MCD), but the presence of anti-nephrin antibodies in Japanese childhood idiopathic nephrotic syndrome (INS) has not been investigated. Methods Anti-nephrin antibodies were measured by ELISA in paired plasma samples obtained from 14 Japanese pediatric patients with INS (male/female: 8/6), at onset (active disease) and following steroid monotherapy. Results The median age at the onset was 75.5 months (interquartile range (IQR): 45-113). Steroid sensitivity resulted in complete remission in 13 patients and almost complete remission in one patient after 4 weeks of glucocorticoid monotherapy. Circulating anti-nephrin antibodies were detected in seven of 14 patients during active disease. In all cases, anti-nephrin antibodies were significantly reduced following treatment concordant with clinical response. There were no differences between the positive and negative groups in pre-treatment parameters. Of the 13 patients who achieved complete remission, nine had at least one relapse during a median follow-up of 851 days (IQR: 808-973). There was also no significant difference in the relapse-free period after the onset between the two groups (P=0.658). Conclusions We identified circulating anti-nephrin antibodies in half of Japanese pediatric patients with INS at initial presentation, which is higher than has been previously reported in a North American cohort.