Spectrum of renal diseases associated with extreme forms of insulin resistance.

Diabetic nephropathy is the leading cause of ESRD in the United States. Why the pathogenic mechanisms lead to nephropathy in certain patients with type 1 and 2 diabetes and spare others is unclear, but it is clear that hyperglycemia and glomerular hyperfiltration are important factors. In patients with syndromes of extreme insulin resistance, proteinuric forms of renal disease are common, but it is surprising to find that the renal pathology usually is not diabetic nephropathy. For instance, in the lipodystrophy syndromes, membranoproliferative glomerulonephritis type 1 and type 2, focal segmental glomerulosclerosis, and also diabetic nephropathy are seen. In the syndromes of autoantibodies to the insulin receptor, the various forms of lupus glomerulonephritis are seen. Even in patients with type 2 diabetes, the renal pathology may not be diabetic nephropathy. Therefore, in patients with syndromic forms of insulin resistance and type 2 diabetes, renal biopsy has an important role in defining the pathology that leads to proteinuric nephropathy and in formulating a therapeutic approach. It is the purpose of this article to review these unusual aspects of proteinuric nephropathy in patients with diabetes.