Glomerular Permeability activity: Prevalence and prognostic value in pediatric Patients with idiopathic nephrotic syndrome

A circulating factor that increases in vitro glomerular permeability to albumin (P alb ) has been isolated from patients with recurrence of focal segmental glomerulosclerosis in their renal allografts. The prevalence and prognostic significance of permeability activity has not been examined in children with idiopathic nephrotic syndrome (INS). P alb activity level was determined in sera from 26 children with new-onset INS before the initiation of therapy by using an in vitro assay. Permeability factor was considered present if P alb was greater than 0.5. The following clinical and laboratory data for patients were tabulated: demographic information, serum albumin and cholesterol concentrations, calculated glomerular filtration rate, age at disease onset, response to corticosteroid treatment, and long-term outcome. Patients ranged in age from 2 to 18 years, and 19 patients (73%) were male. Mean P alb was 0.45 +/- 0.04 (SEM). P alb in patients with a steroid-responsive course (n = 17) did not differ from that of patients with steroid-resistant disease (n = 9). Percentages with P alb greater than 0.5 did not differ between patients with steroid-responsive and steroid-resistant disease (47% and 33%, respectively). P alb was determined after 41 +/- 5 months in 6 patients with steroid-responsive INS. These patients had normal serum creatinine concentrations, and 4 of 6 patients were in prolonged remission. P alb at the onset of INS before therapy was 0.51 +/- 0.09 (P alb > 0.5 in 2 patients) and was not changed at follow-up (P alb = 0.40 +/- 0.12; P alb > 0.5 in 2 patients). Permeability activity, defined as P alb greater than 0.5, is present in pretreatment serum samples from nearly half the children with INS. The presence of permeability activity does not predict clinical response to steroid treatment, renal histopathologic characteristics, or clinical outcome at up to 5 years of follow-up.