Mesangial alterations in steroid-responsive minimal change nephrotic syndrome.

Renal biopsies from 25 children with steroid-sensitive minimal change nephrotic syndrome were evaluated retrospectively to determine whether there is any relation between the morphological changes and the frequency of relapses. Biopsy material was examined by light-, immunofluorescence-, and electron microscopy, and by morphometric methods. The patients were divided in a group of 15 children with frequent relapses (FR) and another group of 10 children with an absence of, or only infrequent, relapses (NR/IR). Semiquantitative evaluation of biopsy specimens disclosed no significant differences between groups, but morphometric measurements performed on toluidine stained semi-thin sections showed a significant increase of mesangial nuclei in FR compared with NR/IR (P less than 0.01). Furthermore, the mean area of mesangial nuclei was decreased and the relative frequency of smaller nuclear profiles was higher in patients with FR compared to NR/IR (p less than 0.01). These findings suggest mesangial cell activation in FR which may be related to a longer course of the disease prior to renal biopsy (mean 4.0 years in FR vs. 1.4 years in NR/IR). In our opinion, morphometric assessment of discrete mesangial alterations is a promising method for exploring clinicopathological correlations in minimal change nephrotic syndrome.