Diabetic glomerulopathy: unusual patterns and dual disease.

Diabetic glomerulopathy is a well-recognized consequence of both type I and type II diabetes. Occasionally, pathologic diagnosis may be challenging for the pathologist. These circumstances include atypical light microscopy or diabetic change with a second superimposed glomerulopathy (dual disease). We have compiled a selection of 12 renal biopsies from diabetic patients that show either an unusual pattern of nephropathy or "dual disease," as well as 2 cases in which the patient had no history of diabetes but had renal biopsies exhibiting changes consistent with diabetic nephropathy. The salient diagnostic features are discussed. To accurately assess these biopsies, immunofluorescence and electron microscopy become essential, and a broadened differential diagnosis must be considered.