Accumulation of laminin and type IV collagen in the kidney in congenital nephrosis.

The aim of this study was to evaluate qualitatively the occurrence of the basement membrane proteins laminin and type IV collagen in the kidneys of ten infants with congenital nephrotic syndrome of the Finnish type (CNF) aged from 3 to 23 months and to compare the results with those for age-matched controls. A slow accumulation of basement membrane (BM) material occurred in the glomerular mesangium, the peripheral capillaries, around atrophied tubules, and the renal vessels in the course of the disease. The staining pattern of accumulated material depended on the duration of the disease and subsequent renal parenchymal damage. Young CNF patients with slight morphological changes in the kidney had only focal and minimal increases in the amounts of mesangial matrix, but as the disease advanced, so the BMs of the glomerular capillaries, renal arteries, and atrophied tubules also became involved and were thicker than normal. The staining reaction was in all patients similar with antibodies against the fragment P1 of laminin and the 7-S domain of type IV collagen. The accumulation of BM material in CNF kidneys is regarded as a secondary phenomenon induced by an unknown pathogenetic defect in the metabolism of some BM component.