RESUMO
<p><b>OBJECTIVE</b>To investigate the pathologic features and diagnostic algorithm of light chain nephropathy (LCN).</p><p><b>METHODS</b>Seven cases of LCN were studied by light microscopy, electron microscopy and immunolabeling of light chains (kappa, lambda) by immunofluorescence and immunoelectron microscopy.</p><p><b>RESULTS</b>The histopathology of 7 cases by light microscopy was variable, with 3 cases showing nodular glomerulosclerosis, 1 case showing mild to moderate mesangial proliferation, and 3 cases showing cast nephropathy with minimal glomerular change. Immunofluorescence study revealed positive staining of a single type of light chain in mesangium (nodular pattern) or along glomerular basement membrane (linear), along tubular basement membrane and around arteriolar walls in all the 7 cases. Ultrastructurally, electron-dense granular deposits were identified in mesangium, subendothelial aspect of glomerular basement membrane, outer aspect of tubular basement membrane and arteriolar walls. Immunogold labeling of light chains showed distinct labeling of a single type light chain in the granular electron-dense materials (5 cases being kappa-positive and 2 being lambda-positive).</p><p><b>CONCLUSIONS</b>LCN typically shows nodular glomerulosclerosis. The ultrastructural change is characteristic and important for diagnosis. Immunolabeling of light chains by immunofluorescence and immunoelectron microscopy carries further diagnostic value, especially in cases with minimal light microscopic change.</p>