Changing patterns in the histopathology of idiopathic nephrotic syndrome in children

Background. It is widely accepted that minimal change nephrotic syndrome (MCNS) is the most common cause of nephrosis in children. Recent studies have demonstrated an increasing incidence of focal segmental glomerulosclerosis (FSGS) in adults. Methods. To determine possible changes in the etiology of childhood nephrosis, the clinical charts of 152 pediatric patients diagnosed with idiopathic nephrotic syndrome between 1978 and 1997 were reviewed. Histopathological diagnosis was available in 105 patients. Results. MCNS was present in 35% of all biopsies, whereas FSGS was observed in 31%. Even if we assume that all patients without a histological diagnosis had MCNS (presumptive MCNS), the total incidence of MCNS (biopsy proven + presumptive) in our population was only 55%. We observed a dramatic increase in the incidence of FS GS during recent years. Before 1990, FSGS was diagnosed in 23% of all renal biopsies but increased to 47% afterward (P = 0.02). This pattern was observed in all ethnic groups. In African Americans, there was a trend for an increase in the incidence of FSGS from 38% before 1990 to 69% after 1990. A similar trend was observed in Caucasians (from 20 to 45%) and Hispanics (from 8 to 33%). Hispanics had the highest incidence of MCNS (biopsy proven + presumptive: 73%), followed by Caucasians (53%) and African Americans (37%). The mean age for presentation of nephrotic syndrome in African Americans (8.0 +/- 0.9 years) was higher than in Caucasians (4.1 +/- 0.05) and Hispanics (3.3 +/- 0.5). Conclusions. Our study showed that the incidence of FSGS in children with idiopathic nephrotic syndrome has increased recently. Furthermore, in African American children, FSGS is the most common cause of nephrotic syndrome. These findings may have significant implications in the management of childhood nephrotic syndrome.