Massive obesity and nephrotic proteinuria with a normal renal biopsy

The association between massive obesity and nephrotic syndrome has been rarely reported. We herein describe a patient with massive obesity (209 kg) and nephrotic proteinuria who had a normal renal biopsy. The patient was initially polycythemic and had a supranormal creatinine clearance. After losing 89 kg, his hemoglobin and creatinine clearance returned to normal, and proteinuria decreased to 300 mg/24 h. We postulated that increases in glomerular hydrostatic pressure may result in local alterations of glomerular basement membrane sieving characteristics (biologic membrane thixotropy) with resultant nephrotic proteinuria. Prompt remission of proteinuria with weight loss supports a reversible glomerular hemodynamic alteration as a mechanism for the proteinuria of massive obesity.