Three patients with steroid-resistant idiopathic nephrotic syndrome were studied at onset and during recurrent nephrotic syndrome after renal transplantation. Renal biopsies at the onset of the nephrotic syndrome showed typical features of the idiopathic nephrotic syndrome; no or minimal focal glomerular abnormalities were present by light microscopy and glomerular-basement-oriented deposits were not demonstrated by immunofluorescent or electron microscopy. Progression to renal failure occurred in 2, 2, and 6 years. Recurrence of nephrotic syndrome was noted 1, 11/2, and 5 months after transplantation. Renal biopsies done 11/2, 5, and 7 months after transplantation when proteinuria was 12·8, 7·6, and 8·5 g. per 24 hours, respectively, showed minimal or no glomerular abnormalities by light microscopy. Immunofluorescent and electron microscopic studies revealed no evidence suggesting immunological injury. Subsequent kidney specimens after transplantation obtained from two of these patients with recurrent nephrotic syndrome showed focal segmental glomerulosclerosis limited primarily to the juxtamedullary glomeruli-a feature further suggesting recurrence of the original disease in the transplanted kidney. These observations suggest that the pathogenesis of the steroid-resistant idiopathic nephrotic syndrome may involve systemic circulating factors; this hypothesis would account for development of a recurrent nephrotic syndrome in the transplanted kidney.
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