Diabetic nephropathy with crescents

Crescent in a diabetic glomerulus

Diabetic nephropathy (DN) do not usually require kidney biopsy for diagnosis. The history of diabetes and the presence of diabetic retinopathy are suffice. However, when other glomerular disease is suspected, the biopsy is performed. These diabetic patients usually have sudden onset of nephrotic syndrome and/or hematuria. Add-on glomerular diseases such as membranous nephropathy, acute postinfectious glomerulonephritis were found in biopsies from these patients. Hower, no lesion other than DN were found in a lot of them.

When crescents are identified in biopsy with well-defined features of DN, the pathologist will search for evidence of glomerular disease superimposing on DN. Similar to biopsies without diabetic changes, the usual suspects for crescentic glomerulonephritis can be found in diabetic kidneys. Immunofluorescence can identify immune complex disease such as IgA nephropathy or acute postinfectious glomerulonephritis and anti-glomerular basement membrane (Goodpasture) disease. The real problem is pauci-immune (ANCA-associated) glomerulonephritis in which no or minimal amount of immune complex is detected by immunofluorescence or electron microscope. When clinical findings such as extrarenal manifestations of the disease and the serological evidence of ANCA are present, the diagnosis of ANCA-associated GN can be made. In the absence of clinical and serological findings, it is difficult to make this diagnosis. The situation is rather different in non-diabetic kidney with crescents, the pathologist may be more comfortable to call it pauci-immune GN though no clinical or serological findings are present.

Otani et al. demonstrated a case of diabetic nephropathy with crescents. No immune complex, ANCA or its extrarenal manifestations were found. The authors argued for the link between microvascular injury in DN and crescent formation and suggested further investigation to establish this link.