Histopathologic variability of the congenital nephrotic syndrome.

Five cases of congenital nephrotic syndrome (CNS) were studied with light microscopic (LM), transmission electron microscopic (TEM) and immunofluorescence microscopic (IFM) techniques. All patients, aged between three weeks and one year, had a nephrotic syndrome (NS) and died soon after the diagnosis. Three patients showed mesangial proliferation, thinning of glomerular basement membranes (GBM) and no deposits by IFM or TEM. They probably represent variants of the Finnish type of CNS. One patient had diffuse sclerosis of the mesangium, irregular and thickened GBMs and electron dense deposits, consistent with the diagnosis of diffuse mesangial sclerosis (DMS). The fifth case also showed changes suggestive of DMS, but was clinically atypical, with an early onset and rapid course. Our findings confirm the morphologic heterogeneity of the CNS and point out the difficulties of classification based on clinical and histological manifestations.