A case of "hidden" diabetic nephropathy diagnosed by a combination of renal biopsy findings and continuous glucose monitoring system.

Although diabetic nephropathy is a microvascular complication of diabetes mellitus, some reports suggest that renal biopsy often shows this pathological change without a diagnosis of diabetes mellitus. Here, we report a case of a 65-year-old man who presented with proteinuria, hypoalbuminemia and hypertension without a diagnosis of diabetes mellitus. He drank alcohol regularly and was a heavy smoker. Renal biopsy revealed a diffuse increase in the mesangial area, mesangial nodules or well-developed hyalinosis, interstitial fibrosis, and arteriosclerosis consistent with the changes of diabetic nephropathy. Although we had initially diagnosed him with idiopathic nodular glomerulosclerosis, use of a continuous glucose monitoring system (CGMS) revealed that the changes in his daily blood glucose concentrations met with the diagnostic criteria of diabetes mellitus. Accordingly, we diagnosed him with diabetic nephropathy and initiated treatment for diabetes mellitus. This case suggests that some cases of diabetic nephropathy may be hidden among patients with impaired glucose tolerance, who are not diagnosed with diabetes mellitus. Use of a CGMS may be helpful in diagnosing this type of "hidden" diabetes mellitus. In addition to diet therapy, smoking control, treatment for hypertension, and strict control of hyperglycemia may be important for these patients.