Is focal segmental glomerulosclerosis increasing in patients with nephrotic syndrome?

Idiopathic nephrotic syndrome in children has conventionally been associated with minimal change disease. However, recent reports have conflictingly suggested that the frequency of focal segmental glomerulosclerosis (FSGS) in children might be on the increase, as has occurred in adults. The aim of the present work was to review the medical literature to ascertain whether an increase in the frequency of FSGS is occurring and, if so, to quantify such increase. We reviewed the studies comparing the frequency of FSGS in two consecutive periods over the past three decades (period 1 versus period 2). We pooled the data of the studies and then estimated FSGS frequency in two ways: (a) including in the denominator all patients with nephrotic syndrome and (b) including only patients who had undergone kidney biopsy. Both analyses were aimed to determine the odds ratio of FSGS occurrence in the second period. Six studies fulfilled the inclusion criteria, involving 1,149 patients with nephrotic syndrome. Four studies were used to calculate FSGS frequency, including in the denominator all nephrotic patients (n = 885), yielding an odds ratio of 2.22 (95% CI = 1.18-4.18). The analysis combining five studies with the number of biopsies in the denominator (n = 603) produced an odds ratio of 1.98 (95% CI = 1.12-3.50). These results suggest that a shift in the pathological pattern of nephrotic syndrome in children might be occurring, resulting in an increase in FSGS frequency. This hypothesis has major clinical significance due to the poorer prognosis associated with FSGS.